公路通行能力外文翻译文献
Chap05 道路通行能力
Highway Capacity
交通运输学院 王正武
00六年三月二十九日 二00六年三月二十九日
1概述
1.1研究的意义 1.1研究的意义
公路通行能力研究 交通流特性研究 可行性研究 交通构成 车速分布 三参数关系 换算系数 公路勘察设计 公路网规划
通行能力研究 基本路段 交叉路口
工程项目后评估
3.2.4匝道通行能力 3.2.4匝道通行能力
同路段的方法
3高速公路通行能力
3.2.5匝道服务水平 3.2.5匝道服务水平
一级服务水平：车流密度很小，车辆自由行驶，不存 在 一级服务水平：车流密度很小，车辆自由行驶， 相互干扰，车流状态为自由畅通， 相互干扰，车流状态为自由畅通，车辆以近于自由流速的速 度行驶； 度行驶； 二级服务水平：交通流中出现车队，车辆之间出现干扰， 二级服务水平：交通流中出现车队，车辆之间出现干扰， 由于头车原因出现少量排队现象，但排队率还很小， 由于头车原因出现少量排队现象，但排队率还很小，车辆行 驶速度仍很快； 驶速度仍很快； 三级服务水平：车流已经出现不稳定现象， 三级服务水平：车流已经出现不稳定现象，车队长度增 已接近匝道通行能力，车队中加减速频繁， 加，已接近匝道通行能力，车队中加减速频繁，车流状态为 连续不断，车辆行驶速度明显下降； 连续不断，车辆行驶速度明显下降； 四级服务水平：交通流非常不稳定，常常出现停车现象， 四级服务水平：交通流非常不稳定，常常出现停车现象， 非常小的流量变化将严重影响整个匝道的运行质量， 非常小的流量变化将严重影响整个匝道的运行质量，相互间 车头时距处于连续流的临界值，车流状态为饱和。 车头时距处于连续流的临界值，车流状态为饱和。
区间观测法
观 点A 测
观 点B 测
交通工程专业外文翻译外文文献英文文献
土木工程学院交通工程专业中英文翻译Road Design专业：交通工程英文原文The Basics of a Good RoadWe have known how to build good roads for a long time. Archaeologists have found ancient Egyptian roadsthat carried blocks to the pyramids in 4600 BCE. Later,the Romans built an extensive road system, using the same principles we use today. Some of these roads are still in service.If you follow the basic concepts of road building, you will create a road that will last. The ten commandments of a good road are:（1）Get water away from the road（2）Build on a firm foundation（3）Use the best materials（4）Compact all layers properly（5）Design for traffic loads and volumes（6）Design for maintenance（7）Pave only when ready（8）Build from the bottom up（9）Protect your investment（10）Keep good records1．Get water away from the roadWe can’t overemphasize the importance of good drainage.Engineers estimate that at least 90% of a road’s problems can be related to excess water or to poor waterdrainage. Too much water in any layer of a road’sstructure can weaken that la yer, leading to failure.In the surface layer, water can cause cracks and potholes. In lower layers it undermines support, causing cracks and potholes. A common sign of water in an asphalt road surface is alligator cracking — an interconnected pattern of cracks forming small irregular shaped pieces that look like alligator skin. Edge cracking, frost heaves, and spring breakup of pavements also point to moistureproblems.To prevent these problems remember that water:• flows downhill• needs to flow somepla ce• is a problem if it is not flowingEffective drainage systems divert, drain and dispose of water. To do this they use interceptor ditches and slopes,road crowns, and ditch and culvert systems.Divert —Interceptor ditches, located between the road and higher ground along the road, keep the water from reaching the roadway. These ditches must slope so they carry water away from the road.Drain —Creating a crown in the road so it is higher along the centerline than at the edges encourages water to flow off the road. Typically a paved crown should be 1⁄4" higher than the shoulder for each foot of width from the centerline to the edge. For gravel surfaces the crown should be 1⁄2" higher per foot of width. For this flow path to work, the road surface must be relatively water tight. Road shoulders also must be sloped away from the road to continue carrying the flow away. Superelevations (banking) at the outside of curves will also help drainthe road surface.Dispose —A ditch and culvert system carries water away from the road structure. Ditches should be at least one foot lower than the bottom of the gravel road layer that drains the roadway. They must be kept clean and must be sloped to move water into natural drainage. If water stays in the ditches it can seep back into the road structure and undermine its strength. Ditches should also be protected from erosion by planting grass, or installing rock and other erosion control measures. Erosion can damage shoulders and ditches, clog culverts, undermine roadbeds, and contaminate nearby streams and lakes. Evaluate your ditch and culvert system twice a year to ensure that it works. In the fall, clean out leaves and branches that can block flow. In spring, check for and remove silts from plowing and any dead plant material left from the fall.2．Build on a firm foundationA road is only as good as its foundation. A highway wears out from the top down but falls apart from the bottom. The road base must carry the entire structure and the traffic that uses it.To make a firm foundation you may need to stabilize the roadbed with chemical stabilizers, large stone called breaker run, or geotextile fabric. When you run into conditions where you suspect that the native soil is unstable, work with an engineer to investigate the situation and design an appropriate solution.3．Use the best materialsWith all road materials you “pay now or pay later.” Inferior materials may require extensive maintenance throughout the road’s life. They may also force you to replace the road prematurely.Crushed aggregate is the best material for the base course. The sharp angles of thecrushed material interlock when they are compacted. This supports the pavement and traffic by transmitting the load from particle to particle. By contrast, rounded particles act like ballbearings, moving under loads.Angular particles are more stable than rounded particles.Asphalt and concrete pavement materials must be of the highest quality, designed for the conditions, obtained from established firms, and tested to ensure it meets specifications.4．Compact all layersIn general, the more densely a material is compacted, the stronger it is. Compaction also shrinks or eliminates open spaces (voids) between particles. This means that less water can enter the structure. Water in soil can weaken the structure or lead to frost heaves. This is especially important for unsurfaced (gravel) roads. Use gravel which has a mix of sizes (well-graded aggregate) so smaller particles can fill the voids between larger ones. Goodcompaction of asphalt pavement lengthens its life.5．Design for traffic loads and volumesDesign for the highest anticipated load the road will carry. A road that has been designed only for cars will not stand up to trucks. One truck with 9 tons on a single rear axle does as much damage to a road as nearly 10,000 cars.Rural roads may carry log trucks, milk trucks, fire department pumper trucks, or construction equipment. If you don’t know what specific loads the road will carry, a good rule of thumb is to design for the largest piece of highway maintenance equipment that will be used on the road.A well-constructed and maintained asphalt road should last 20 years without major repairs or reconstruction. In designing a road, use traffic counts that project numbers and sizes of vehicles 20 years into the future. These are only projections, at best, but they will allow you to plan for traffic loadings through a road’s life.6．Design for maintenanceWithout maintenance a road will rapidly deteriorate and fail. Design your roads so they can be easily maintained. This means:• adequate ditches that can be cleaned regularly• culverts that are marked for easy locating in the spring• enough space for snow after it is plowed off the road• proper cross slopes for safet y, maintenance and to avoid snow drifts• roadsides that are planted or treated to prevent erosion• roadsides that can be mowed safelyA rule of thumb for adequate road width is to make it wide enough for a snowplow to pass another vehicle without leaving the travelled way.Mark culverts with a post so they can be located easily.7．Pave only when readyIt is not necessary to pave all your roads immediately. There is nothing wrong with a well-built and wellmaintained gravel road if traffic loads and volume do not require a paved surface. Three hundred vehicles per day is the recommended minimum to justify paving.Don’t assume that laying down asphalt will fix a gravel road that is failing. Before you pave, make sure you have an adequate crushed stone base that drains well and is properly compacted. The recommended minimum depth of crushed stone base is 10" depending on subgrade soils. A road paved only when it is ready will far outperform one that is constructed too quickly.8．Ê Build from the bottom upThis commandment may seem obvious, but it means that you shouldn’t top dress or resurface a road if the problem is in an underlying layer. Before you do any road improvement, locate the cause of any surface problems. Choose an improvement technique that will address the problem. This may mean recycling or removing all road materials down to the native soil and rebuilding everything. Doing any work that doesn’t solve the problem is a waste of money and effort.9．Ê Protect your investmentThe road system can be your municipality’s biggest investment. Just as a home needs painting or a new roof, a road must be maintained. Wisconsin’s severe climate requires more road maintenance than in milder places. Do these important maintenance activities: Surface —grade, shape, patch, seal cracks, control dust, remove snow and iceDrainage —clean and repair ditches and culverts; remove all excess materialRoadside —cut brush, trim trees and roadside plantings, control erosionTraffic service —clean and repair or replace signsDesign roads with adequate ditches so they can be maintained with a motor grader. Clean and grade ditches to maintain proper pitch and peak efficiency. After grading, remove all excess material from the shoulder.10．Keep good recordsYour maintenance will be more efficient with good records. Knowing the road’s construction, life, and repair history makes it much easier to plan and budget its future repairs. Records can also help you evaluate the effectiveness of the repair methods and materials you used.Good record keeping starts with an inventory of the system. It should include the history and surface condition of the roadway, identify and evaluate culverts and bridges, note ditch conditions, shoulders, signs, and such structures as retaining walls and guardrails.Update your inventory each year or when you repair or change a road section. A formal pavement management system can help use these records and plan and budget road improvements.ResourcesThe Basics of a Good Road#17649, UW-Madison, 15 min. videotape. Presents the Ten Commandments of a Good Road. Videotapes are loaned free through County Extension offices.Asphalt PASER Manual(39 pp), Concrete PASER Manual (48 pp), Gravel PASER Manual (32 pp). These booklets contain extensive photos and descriptions of road surfacesto help you understand types of distress conditions and their causes. A simple procedure for rating the condition helps you manage your pavements and plan repairs.Roadware, a computer program which stores and reports pavement condition information. Developed by the Transportation Information Center and enhanced by the Wisconsin Department of Transportation, it uses the PASER rating system to provide five-year cost budgets and roadway repair/reconstruction priority lists.Wisconsin Transportation Bulletin factsheets, available from the Transportation Information Center (T.I.C.).Road Drainage, No. 4. Describes drainage for roadways, shoulders, ditches, and culverts.Gravel Roads, No. 5. Discusses the characteristics of a gravel road and how to maintain one.Using Salt and Sand for Winter Road Maintenance,No. 6. Basic information and practical tips on how to use de-icing chemicals and sand.Culverts—Proper Use and Installation, No. 15. Selecting and sizing culverts, designing, installing and maintaining them.Geotextiles in Road Construction/Maintenance andErosion Control, No. 16. Definitions and common applications of geotextiles on roadways and for erosion control.T.I.C. workshops are offered at locations around the state.Crossroads,an 8-page quarterly newsletter published by the T.I.C. carries helpful articles, workshop information, and resource lists. For more information on any of these materials, contact the T.I.C. at 800/442-4615.中文译文一个良好的公路的基础长久以来我们已经掌握了如何铺设好一条道路的方法，考古学家发现在4600年古埃及使用建造金字塔的石块铺设道路，后来，罗马人使用同样的方法建立了一个庞大的道路系统，这种方法一直沿用到今天。
道路路桥工程中英文对照外文翻译文献
道路路桥工程中英文对照外文翻译文献Asphalt Mixtures: ns。
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道桥专业外文文献翻译
Design of reinforced concrete bridgesP. Jackson Giord and PartnersThe shortest span reinforced concrete decks are built as solid slabs. These may be supported on bearings although, due to durability issues with expansion joints and bearings, it is usually preferable to cast them integral with in-situ abutments or place them as part of pre cast box culverts. As the span increases, the optimum form of construction changes to voided slab or beam and slab then box girder bridges. Open spandrel arches enable relatively long spans, more commonly built in steel or prestressed concrete, to be built efficiently in reinforced concrete. Reinforced concrete is also used for deck slabs and substructures for bridges with main elements of steel or prestressed concrete. The key design criteria and checks required by codes are the same regardless of the form of construction. These are for ultimate strength in flexure, shear and torsion and for serviceability issues including crack widths and service stresses. For elements with significant live load ratios, reinforcement fatigue may sometimes also have to be checked. IntroductionMost modern small bridges are of reinforced concrete construction and nearly all modern bridges contain some elements of reinforced concrete (RC). In this chapter, the design of reinforced concrete bridge superstructures is considered and some aspects of the design criteria for reinforced concrete, which are also relevant to other reinforced concrete substructures and reinforced concrete parts of bridges with steel or prestressed main elements, are reviewed.Some specific aspects which are most often relevant to deck slabs in bridges with prestressed or steel beams will be considered in the section on beam and slab bridges.In situ reinforced concrete construction has the great advantage of simplicity; formwork is placed, reinforcement fixed and concrete poured and the structure is then com-plete. In modern practice, precast bridge elements are usually prestressed. For smaller elements, this is because pretensioning on long line beds is a convenient method of providing the steel. For larger structures, post-tensioning provides the most convenient way of fixing manageable sized elements together. The result is that, with some exceptions which will be discussed, purely reinforced concrete bridges are usually cast in situ.In the following, the various types of RC bridge are considered and the design criteria for reinforced concrete are then reviewed.Solid slab bridgesSingle spansThe solid slab is the simplest form of reinforced concrete bridge deck. Ease of construction resulting from the sim-plicity makes this the most economic type for short span structures. Solid slabs also have good distribution properties which makes them efficient at carrying concentrated movable loads such as wheel loads for highway bridges. However, above a span of around 10m the deadweight starts to become excessive, making other forms of construction more economic.Solid slab bridges can be simply supported on bearings or built into the abutments. Until recently, bridge engineers tended to be quite pedantic about providing for expansion and even bridges as short as 9m span were often provided with bearings and expansion joints. However, bearings and expansion joints have proved to be among the most troublesome components of bridges. In particular, deterior-ation of substructures due to water leaking through expan-sion joints has been common especially in bridges carrying roads where de-icing salt is used.Recently, the fashion has changed back to designing bridges that are cast integral with theabutments or bank seats (Department of Transport, 1995). Apart from the durability advantages, this can lead to saving in the deck due to the advantage of continuity. On short span bridges with relatively high abutment walls, being able to use the deck to prop the abutments can also lead to significant savings in the abutments. However, this normally depends on being able to build the deck before backfilling behind the abutments. When assumptions about construction approach such as this are made in design, it is important that they should be properly conveyed to the contractor, normally by stating them on the drawings.A feature of the design of integral bridges which has not always been appreciated is that, because the deck is not structurally isolated from the substructure, the stress state in the deck is dependent on the soil properties. This inevitably means that the analysis is less ‘accurate’than in conventional structures. Neither the normal at-rest pressure behind abutments nor the resistance to movement is ever very accurately known. It might be argued that, because of this, designs should be done for both upper and lower bounds to soil properties. In practice, this is not generally done and the design criteria used have sufficient reserve so that this does not lead to problems.Depending on the ground conditions, span and obstacle crossed, the abutments of asingle-span bridge may be separate or may be joined to form a complete box. Such box type structures have the advantage that they can be built without piles even in very poor ground, as the bearing pressure is low. Since the box structure is likely to be lighter than the displaced fill, the net bearing pressure is often negative. This can lead to problems in made ground as the embankment either side of the box may settle much more than the box, leading to problems with vertical align-ment and damage to the surfacing or rails over the bridge.RC slab bridges are normally cast in situ. An exception is very short span shallower structures (typically up to some 6m span and 3.6m clear height) which can be most eco-nomically precast effectively complete as box culverts, leav-ing only parapets and, where required, wing walls to cast in situ. This form of construction is most commonly used for conveying watercourses under embankments but can be used for footway and cycletracks.In situ construction is very convenient for greenfield sites and for crossing routes that can be diverted. It is less con-venient for crossing under or over live routes. For the latter, spanning formwork can be used if there is sufficient headroom. However, in many cases beam bridges are more convenient and the precast beams will normally be pre-stressed. RC box type structures can, however, be installed under live traffic. They can be pushed under embankments. The issues are considered by Allenby and Ropkins (2004). A reasonable amount of fill over the box is needed to do this under live traffic. The box structure is cast adjacent to its final position and then jacked into position with anti-drag ropes preventing the foundations below and the fill above moving with it. If there is not much fill depth, it becomes impractical to push the box whilst keeping a road or rail route over the top still. A similar approach can, how-ever, be used with the box cast in advance and then jacked into place in open cut over a relatively short possession.Multiple spansIn the past, some in situ multi-span slab bridges were built which were simply supported. However, unlike in bridges built from precast beams, it is no more complicated to build a continuous bridge. Indeed, because of the absence of the troublesome and leak-prone expansion joints, it may actually be simpler. It is therefore only in exceptional circumstances (for example construction in areas subject to extreme differential settlement due to mining subsidence) thatmultiple simply supported spans are now used.Making the deck continuous or building it into the abut-ments also leads to a significant reduction in the mid-span sagging moments in the slab.The advantage of this continuity in material terms is much greater than in bridges of pre-stressed beam construction where creep redistribution effects usually more than cancel out the saving in live load moments.Various approaches are possible for the piers. Either leaf piers can be used or discrete columns. Unlike in beam bridges, the latter approach needs no separate transverse beam. The necessary increase in local transverse moment capacity can be achieved by simply providing additional transverse reinforcement in critical areas. This facility makes slab bridges particularly suitable for geometrically complicated viaducts such as arise in some interchanges in urban situations. Curved decks with varying skew angles and discrete piers in apparently random locations can readily be accommodated.Whether discrete columns or leaf piers are used, they can either be provided with bearings or built into the deck. The major limitation on the latter approach is that, if the bridge is fixed in more than one position, the pier is subject to significant moments due to the thermal expansion and contraction of the deck. Unless the piers are very tall and slender, this usually precludes using the approach for more than one or two piers in a viaduct.Voided slab bridgesAbove a span of about 10–12m, the dead weight of a solid slab bridge starts to become excessive. For narrower bridges, significant weight saving can be achieved by using relatively long transverse cantilevers giving a bridge of ‘spine beam’form as shown in Figure 1. This canextend the economic span range of this type of structure to around 16m or more. Above this span, and earlier for wider bridges, a lighter form of construction is desirable.One of the commonest ways of lightening a solid slab is to use void formers of some sort. The commonest form is circular polystyrene void formers. Although polystyrene appears to be impermeable, it is only the much more expensive closed cell form which is so. The voids should therefore be provided with drainage holes at their lower ends. It is also important to ensure that the voids and reinforcement are held firmly in position in the formwork during construction. This avoids problems that have occurred with the voids floating or with the links moving to touch the void formers, giving no cover.Provided the void diameters are not more than around 60% of the slab thickness and nominal transverse steel is provided in the flanges, the bridge can be analysed much as a solidslab. That is, without considering either the reduced transverse shear stiffness or the local bending in the flanges. Unlike the previous British code, EN 1992-2 (BSI, 2005) does not give specific guidance on voided slabs. However, some is provided in the accompanying ‘PD’pub- lished by the British Standards Institution (BSI, 2008a).The section is designed longitudinally in both flexure and shear allowing for the voids. Links should be provided and these are designed as for a flanged beam with the minimum web thickness.The shear stresses are likely to become excessive near supports, particularly if discrete piers are used. However, this problem can be avoided by simply stopping the voids off, leaving a solid section in these critical areas.If more lightening is required, larger diameter voids or square voids forming a cellular deck can be used. These do then have to be considered in analysis. The longitudinal stiff-ness to be used for a cellular deck is calculated in the normal way, treating the section as a monolithic beam.Transversely, such a structure behaves quite differently under uniform and non-uniform bending. In the former, the top and bottom flanges act compositely whereas in the latter they flex about their separate neutral axes as shown in Figure 2. This means the correct flexural inertia can be an order of magnitude greater for uniform than non-uniform bending. The behaviour can, however, be modelled in a conventional grillage model by using a shear deformable grillage. The composite flexural properties are used and the extra defor-mation under non-uniform bending is represented by calcu-lating an equivalent shear stiffness.Having obtained the moments and forces in the cellular structure, the reinforcement has to be designed. In addition to designing for the longitudinal and transverse moments on the complete section, local moments in the flanges have to be considered. These arise from the wheel loads applied to the deck slab and also from the transverse shear. This shear has to be transmitted across the voidsby flexure in the flanges, that is by the section acting like a vierendeel frame as shown in Figure 2.Voided slab bridges typically have the rather utilitarian appearance typical of bridges with the type of voided section shown in Figure 1 and with either single spans or with intermediate piers of either leaf or discrete vertical pier form. However, one of the potential great advantages of concrete is that any shape can be formed. Figure 3 shows a voided slab bridge of more imaginative appearance which carries main line rail loading. To make most efficient use of the curved soffit varying depth section, different sizes of void were used across the width.Beam and slab bridgesIn recent years, in situ beam and slab structures have been less popular than voided slab forms, while precast beams have generally been prestressed. Reinforced beam andslab structures have therefore been less common. However, there is no fundamental reason why they should not be used and there are thousands of such structures in service.One of the disadvantages of a beam and slab structure compared with a voided slab or cellular slab structure is that the distribution properties are relatively poor. In the UK at least, this is less of a disadvantage than it used to be. This is because the normal traffic load has increased with each change of the loading specification, leaving the abnormal load the same until the most recent change which could actually make it less severe for shorter spans. However, reinforced concrete beam and slab bridges do not appear to have increased in popularity as a result. They are more popular in some other countries.The relatively poor distribution properties of beam and slab bridges can be improved by providing one or more transverse beams or diaphragms within the span, rather than only at the piers. In bridges built with precast beams, forming these ‘intermediate diaphragms’is extremely inconvenient and therefore expensive so they have become unusual. However, in an in situ structure which has to be built on falsework, it makes relatively little difference and is therefore more viable.The beams for a beam and slab structure are designed for the moments and forces from the analysis. The analysis is now usually computerised in European practice, although the AASHTO (2002) code encourages the use of a basically empirical approach.Having obtained the forces, the design approach is the same as for slabs apart from the requirement for nominal links in all beams. Another factor is that if torsion is consid-ered in the analysis the links have to be designed for torsion as well as for shear. Itis, however,acceptable practiceto use torsionless analysis at least for right decks.Because the deck slab forms a large top flange, the beams of beam and slab bridges are more efficiently shaped for resisting sagging than hogging moments. It may therefore be advantageous to haunch them locally over the piers even in relatively short-span continuous bridges.The biggest variation in practice in the design of beam and slab structures is in the reinforcement of the deck slab. A similar situation arises in the deck slabs of bridgeswhere the main beams are steel or prestressed concrete and this aspect will now be considered.Conventional practice in North America was to design only for the moments induced in the deck slab by its action in spanning between the beams supporting wheel loads (the ‘local moments’). These moments were obtained from Westergaard (1930) albeit usually by way of tables given in AASHTO. British practice also uses elastic methods to obtain local moments, usuallyeither Westergaard or influ-ence charts such as Pucher (1964). However, the so-called‘global transverse moments’, the moments induced in the deck slab by its action in distributing load between the beams, are considered. These moments, obtained from the global analysis of the bridge, are added to the local moments obtained from Westergaard (1930) or similar methods. Only‘co-existent’moments (the moments induced in the same part of the deck under the same load case) are considered, and the worst global and local moments often do notcoin-cide. However, this still has a significant effect. In bridges with very close spaced beams (admittedly rarely used in North America) the UK approach can give twice the design moments of the US approach.Although the US approach may appear theoretically unsound (the global moments obviously do exist in American bridges), it has produced satisfactory designs.One reason for this is that the local strength of the deck slabs is actually much greater than conventional elastic analysis suggests. This has been extensively researched (Hewit and Batchelor, 1975; Holowka and Csagoly, 1980;Kirkpatrick et al., 1984).In Ontario (Ontario Ministry of Transportation and Communications, 1983) empirical rules have been devel-oped which enable such slabs to be designed very simply and economically. Although these were developed without major consideration of global effects, they have been shown to work well within the range of cases they apply to (Jack-son and Cope, 1990). Similar rules have been developed in Northern Ireland (Kirkpatrick et al., 1984) and elsewhere but they have not been widely accepted in Europe.Longer span structuresIn modern practice, purely reinforced structures longer than about 20m span are quite unusual; concrete bridges of this size are usually prestressed. However, there is no funda-mental reason why such structures should not be built.The longest span reinforced concrete girder bridges tend to be of box girder form. Although single cell box girders are a well-defined form of construction, there is no clear-cut distinction between a ‘multi-cellular box girder’and a voided slab. However, the voids in voided slab bridges are normally formed with polystyrene or other permanent void formers, whereas box girders are usually formed with removable formwork. The formwork can only be removed if the section is deep enough for access, which effectively means around 1.2m minimum depth. Permanent access to the voids is often provided. In older structures, this was often through manholes in the top slab. This means traffic management is required to gain access and also means there is the problem of water, and de-icing salt where this is used, leaking into the voids. It is therefore preferable to provide access from below.In a continuous girder bridge (particularly one with only two spans) the hogging moments, particularly the perma-nent load moments, over the piers are substantially greater than the sagging moments at mid-span. This, combinedwith the greater advantage of saving weight near mid-span, encourages longer span bridges to be haunched. Haunching frequently also helps with the clearance required for road, rail or river traffic under the bridge by allowing a shallower section elsewhere.The longest span and most dramatic purely reinforced concrete bridges are open spandrel arches as in the Catha-leen’s Falls Bridge shown in Figure 4. The true arch form suits reinforced concrete well as the compressive force in the arch rib increases its flexural strength. As a result, the form is quite efficient in terms of materials.Because of the physical shape of the arch and the require- ment for good ground conditions to resist the lateral thrust force from the arch, this form of construction is limited in its application. It is most suitable for crossing valleys in hilly country. The simplest way to build such a structure is on falsework. However, the falsework required is very extensive and hence relatively expensive. Because of this, such bridges are often more expensive than structurally less efficient forms, such as prestressed cantilever bridges, that can be built with less temporary works. However, they may still be economic in some circumstances, particularly in countries where the labour required to erect the falsework is relatively cheap. A further factor may be local availability of the materials in countries where the prestressing equip-ment or structural steelwork required for other bridges of this span range would have to be imported.It is also possible to devise other ways of building arches.They have been built out in segments from either end supported by tying them back with temporary stays. Another approach, which is only likely to be viable with at least three spans, is to insert temporary diagonal mem- bers so that the bridge, including the columns supporting the deck and at least main longitudinal members at deck level, can be built bay by bay behaving as a truss until it is joined up.The efficiency of arch structures, like other forms used for longer span bridges, arises because the shape is optimised for resisting the near-uniform forces arising from dead load which is the dominant load. The profile of the arch is arranged to minimise the bending moments in it. Theoretically, the optimum shape approximates to a catenary if the weight of the rib dominates or a parabola if the weight of the deck dominates but the exact shape is unlikely to be critical.Arch structures can be so efficient at carrying dead weight that applying the usual load factor for dead load actually increases live load capacity by increasing the axial force in, andhence flexural capacity of, the rib. The design code’s lesser load factor (normally 1.0) for‘relieving effects’should be applied to dead weight when this arises. However, the letter of many codes only requires this to be applied in certain cases which are defined in such a way that it does not appear to apply here. This cannot be justified philosophi-cally and the reduced factor should be used.Because the geometry is optimised for a uniform load,loading the entire span is unlikely to be the critical live load case, unlike in a simple single-span beam bridge. It will normally be necessary to plot influence lines to determine the critical case. For uniform loads, this is often loading a half-span.Arch bridges have been built in which the live load bending moments are taken primarily by the girders at deck level, enabling the arch ribs to be very slim in appear-ance. However, the more usual approach is to build the arch rib first and then build the deck structure afterwards, possibly even after the falsework has been struck so that this does not have to be designed to take the full load.The deck structure is then much like a normal viaduct supported on piers from the arch rib and the rib has to take significant moments.In the past, reinforced concrete truss structures have also been built but they are not often used in modern practice because the building costs are high due to the complexity of formwork and reinforcement.Design calculationGeometryThe shape of reinforced concrete bridges is usually decided by experience aided by typical span-to-depth ratios. The design calculations are only really used to design the reinforcement. A typical simply supported slab has a span-to-depth ratio of around 10–15 but continuous or integral bridges can be shallower. Because the concentrated live load (i.e. the wheel load) the deck has to carry does not reduce with span, the span-to-depth ratio of short span slabs tends to be towards the lower end of the range.However, deck slabs of bigger bridges often have greater span-to-depth ratios than slab bridges. This is economic because the dead weight of the slab, although an insignifi-cant part of the load on the slab, is significant to the global design of the bridge.There was a fashion for very shallow bridges in the 1960s and 1970s as they were considered to look more elegant. However, unless increasing the construction depth has major cost implications elsewhere (such as the need to raise embankments) it is likely to be more economic to use more than the minimum depth. The appearance dis-advantage on short span bridges can be resolved by good detailing of the edges. Bridge decks with short transverse cantilevers at the edges tend to look shallower than vertical sided bridges even if they are actually deeper.Having decided the dimensions of the bridge, the design calculations then serve primarily to design the reinforce-ment and the key checks will now be considered. They will be illustrated mainly by considering slab structures but most of the principles apply to all reinforced concrete. Ultimate strength in flexure and torsionReinforced concrete is normally designed for ultimate strength in flexure first. This is partly because this is usually, although not invariably, the critical design criterion.Another reason is that reinforcement can be more readily designed directly for this criterion. For other criteria, suchas crack width or service stresses, a design has to be assumed and then checked. This makes thedesign process iterative. A first estimate is required to start the iterative procedure and the ultimate strength design provides such an estimate.Although other analytical methods give better estimates of strength, elastic analysis is usually used in design. This has to be used when checking serviceability criteria. Because of this, the use of more economic analyses at the ultimate limit state (such as yield-line analysis) invariably results in other criteria (such as cracking or stress limits) becoming critical leaving little or no advantage.Concrete slabs have to resist torsion as well as flexure. However, unlike in a beam, torsion and flexure in slabs are not separate phenomena. They interact in the same way that direct and shear stresses interact in plane stress situations. They can be considered in the same way: thatis using Mohr’s circle. Theoretically, it is most efficient to use orthogonal reinforcement placed in the directions of maximum and minimum principal moments. Since there is no torsion in these directions, torsion does not then have to be considered. However, it is not often practical to do this as the principal moment directions change with both position in the slab and load case.In right slabs the torsional moments in the regions (the elements of the computer model where this is used),where the moments are maximum, are relatively small and can often be ignored. In skew slabs, in contrast, the torsions can be significant. The usual approach is to design for an increased equivalent bending moment in the reinforcement directions. Wood (1968) has published the relevant equations for orthogonal steel and Armer (1968) for skew steel. Many of the computer programs commonly used for the analysis of bridge decks have post-processors that enable them to give these corrected moments, com-monly known as ‘Wood–Armer’moments, directly. To enable them to do this, it is necessary to specify the direc-tion of the reinforcement.When the reinforcement is very highly skewed, the Wood–Armer approach leads to excessive requirements for transverse steel. When assessing existing structures, this problem can be avoided by using alternative analytical approaches. However, in design it is usually preferable to avoid the problem by avoiding the use of very highly skewed reinforcement. The disadvantage of this is that it makes the reinforcement detailing of skew slab bridges more complicated. This arises because the main steel in the edges of the slab has to run parallel with the edges. Orthogonal steel can therefore only be achieved in the centre of the bridge either by fanning out the steel or bypro-viding three layers in the edge regions. That is, one parallel to the edge in addition to the two orthogonal layers.When torsion is considered, it will be found that there is a significant requirement for top steel in the obtuse corners even of simply supported slabs. It can be shown using other analytical methods (such as yield-line or torsionless grillage analysis) that equilibrium can be satisfied without resisting these moments. The top steel is therefore not strictly necessary for ultimate strength. However, the moments are real and have caused significant cracking in older slab structures which were built without this steel. It is therefore preferable to reinforce for them. Ultimate strength in shearShear does not normally dictate the dimensions of the element. However, codes allow slabs (unlike beams) which do not have shear reinforcement and it is economically desirable to avoid shear reinforcement in these if e of links is particularly inconvenient in very shallow slabs, such as in box culverts or the deck slabs of beam and slab bridges, and many codes do not allow them to be considered effective. The shear strength rules can therefore be critical in design.。
二级公路毕业设计外文文献
外文资料及翻译Effects of Design Features on Rigid Pavement PerformanceThe performance of rigid pavements is affected by a variety of design features, including slab thickness, base type, joint spacing, reinforcement, joint orientation, load trans fer, dowel bar coatings, longitudinal joint design, joint sealant, tied concrete shoulders ,and subdrainage . A study was made by ERES Consultants, Inc. under FHWA contract on the effects of these features on rigid pavement performance . Ninety-five pavemen tsections located in four major climatic regions were thoroughly evaluated . The following conclusions, which provide some revealing insights into pavement performance, are abstracted from the report (Smith et al., 1990a).Slab Thickness The effect of slab thickness on pavement performance was significant.It was found that increasing slab thickness reduced transverse and longitudinal cracking in all cases. This effect was much more pronounced for thinner slabs than fo rthicker slabs . It was not possible to compare the performance of the thinner slabs and the thicker slabs directly, because the thick slabs were all constructed directly on th esubgrade and the thinner slabs were all constructed on a base course .Increasing the thickness of slab did not appear to reduce joint spalling or join tfaulting . Thick slabs placed directly on the subgrade, especially in wet climates an dexposed to heavy traffic, faulted as much as thin slabs constructed on a base course .Base Type Base types, including base/slab interface friction, base stiffness, base erodibility, and base permeability, seemed to have a great effect on the performance of jointed concrete pavements . The major performance indicators, which were affected by variations in base type, were transverse and longitudinal cracking, joint spalling, and faulting .The worst performing base type, consisted of the cement-treated or soil cement bases, which tended to exhibit excessive pumping, faulting, and cracking. This is most likely due to the impervious nature of the base, which traps moisture and yet can brea- k down and contribute to the movement of fines beneath the slab .The use of lean concrete bases generally produced poor performance . Large curl -ing and warping stresses have been associated with slabs constructed over lean concrete bases. These stresses result in considerable transverse and longitudinal cracking of the slab . The poor performance of these bases can also be attributed to a bathtub design, in which moisture is trapped within the pavement cross section .Dense-graded asphalt-treated base courses ranged in performance from very poor to good. The fact that these types of bases were often constructed as a bathtub design contributed to their poor performance . This improper design often resulted in severe cracking, faulting, and pumping.The construction of thicker slabs directly on the subgrade with no base resulted In a pavement that performed marginally. These pavements were especially susceptible to faulting, even under low traffic levels.Pavements constructed over aggregate bases had varied performance, but were generally in the fair to very good category. In general, the more open-graded the aggregate,the better the performance . An advantage of aggregate bases is that they contribute the least to the high curling and warping stresses in the slab . Even though aggregate bases are not open-graded, they are more permeable and have a lower friction factor than stabilized bases .The best bases in terms of pavement performance were the permeable bases . Typical base courses have permeabilities ranging from 0 to less than 1 ft/day (0 .3 m/day) ; good permeable bases have permeabilities up to 1000 ft/day (305 m/day) . Specific areas of concern were the high corner deflections and the low load transfer exhibited by the permeable bases . These can affect their long-term performance, so the use of dowel bars might be required . An unexpected benefit of using permeable bases was the reduction in "D" cracking on pavements susceptible to this type of distress .Slab Length For JPCP, the length of slabs investigated ranged from 7 .75 to 30 ft(2.4to9.1m). It was found that reducing the slab length decreased both the magnitude of the joint faulting and the amount of transverse cracking. On pavements with random joint spacings, slabs with joint spacings greater than 18 ft (5.5 m) experienced more transverse cracking than did the shorter slabs .For JRCP, the length of slabs investigated ranged from 21 to 78 ft (6 .4 to 23 .9 m) .Generally, shorter joint spacings performed better, as measured by the deteriorated transverse cracks, joint faulting, and joint spalling . However, several JRCP with long joint spacings performed quite well . In particular, the long jointed pavements in New Jersey, which were constructed with expansion joints, displayed excellent performance .An examination of the stiffness of foundation was made through the use of the radius of relative stiffness, f . Generally speaking, when the ratio L/E, where L is the length of slab, was greater than 5, transverse cracking occurred more frequently . Thisfactor was further examined for different base types . It was found that stiffer base courses required shorter joint spacings to reduce or eliminate transverse cracking .Reinforcement The amount of steel reinforcement appeared to have an effect in controlling the amount of deteriorated transverse cracking . Pavement sections with less than 0.1% reinforcing steel often displayed significant deteriorated transverse cracking.A minimum of 0 .1% reinforcing steel is therefore recommended, with larger amounts required for more severe climate and longer slabs.Joint Orientation Conventional wisdom has it that skewed joints prevent the application of two wheel loads to the joint at the same time and thus can reduce load-associated distresses . The results from the limited sample size in this study were ambiguous, but all of the nondoweled sections with skewed joints had a lower PSR than similar designs with perpendicular joints . The available data provide no definite conclusions on the effectiveness of skewing transverse joints for nondoweled slabs . Skewed joints are not believed to provide any benefit to doweled slabs.Load Transfer Dowel bars were found to be effective in reducing the amount of joint faulting when compared with nondoweled sections of comparable designs. The diameter of dowels had an effect on performance, because larger diameter bars provided better load transfer and control of faulting under heavy traffic than did smaller dowels.It appeared that a minimum dowel diameter of 1 .25 in . (32 mm) was necessary to provide good performance .Nondoweled JPCP slabs generally developed significant faulting, regardless of pavement design or climate . This effect was somewhat mitigated by the use of permeable bases. However, the sections in this group had a much lower number of accumulated ESAL, so no definite conclusions can be drawn yet .Dowel Bar Coatings Corrosion-resistant coatings are needed to protect dowels from the adverse effects of moisture and deicing chemicals .While most of the sections in this study did not contain corrosion-resistant dowel bars, those that did generally exhibited enhanced performance. Very little deteriorated transverse cracking was identified on these sections. In fact, one section in New Jersey with stainless steel-clad dowel bars was performing satisfactorily after 36 years of service .Longitudinal Joint Design The longitudinal joint design was found to be a critical design element.Both inadequate forming techniques and insufficient depths of joint can contribute to the development of longitudinal cracking . There was evidence of the ad vantage of sawing the joints over the use of inserts . The depth of longitudinal joints is generally recommended to be one-third of the actual, notdesigned, slab thickness, but might have to be greater when stabilized bases are used .Joint Sealant Joint sealing appeared to have a beneficial effect on performance . This was particularly true in harsh climates with excessive amounts of moisture . Preformed compression sealants were shown to perform well for more than 15 years under heavy traffic.Except where "D" cracking occurred, pavement sections containing preformed sealants generally exhibited little joint spalling and were in good overall conditions.Rubberized asphalt joint sealants showed good performance for 5 to 7 years.Tied Concrete Shoulders It is generally believed that tied concrete shoulders can reduce edge stresses and corner deflections by providing more lateral supports to the mainline pavement, thus improving pavement performance . Surprisingly, this study showed that, although tied concrete shoulders performed better than asphalt shoulders,many of the tied shoulders were not designed properly and actually contributed to poor performance of the mainline pavement . The tiebars were spaced too far apart ,sometimes at a spacing of 40 in.(1016 mm), and were not strategically located near slab corners to provide adequate support . In some cases, tied concrete shoulders were constructed over a stabilized dense-graded base in a bathtub design, resulting in the poor performance of mainline pavement.Subdrainage The provision of positive subdrainage, either in the form of longitudinal edge drains or the combination of a drainage layer and edge drains, generally reduced the amount of faulting and spalling related to "D" cracking . With few exceptions, the load-associated distresses, especially faulting and transverse cracking, decreased as the drainage characteristics improved . The overall pavement performance can be improved by using an open-graded base or restricting the percentage of fines . A filter layer must be placed below the permeable base, and regular maintenance of the outlets must be provided .译文结构特点对刚性路面性能的影响刚性路面的性能受种种结构特点的影响，如板厚、基层类型、接缝间距、钢筋用量、接风方向、荷载传递、传力杆涂层、纵缝设计、接缝填封料、有拉杆混凝土道肩和地下排水等。
道路路桥工程中英文对照外文翻译文献
道路路桥工程中英文对照外文翻译文献中英文资料中英文资料外文翻译(文档含英文原文和中文翻译)原文：Asphalt Mixtures-Applications。
Theory and Principles1.ApplicationsXXX is the most common of its applications。
however。
and the onethat will be XXX.XXX “flexible” is used to distinguish these pavements from those made with Portland cement,which are classified as rigid pavements。
that is。
XXX it provides they key to the design approach which must be used XXX.XXX XXX down into high and low types,the type usually XXX product is used。
The low typesof pavement are made with the cutback。
or emulsion。
XXX type may have several names。
However。
XXX is similar for most low-type pavements and XXX mix。
forming the pavement.The high type of asphalt XXX中英文资料XXX grade.中英文资料Fig.·1 A modern XXX.Fig.·2 Asphalt con crete at the San Francisco XXX.They are used when high wheel loads and high volumes of traffic occur and are。
公路建设外文翻译文献
公路建设外文翻译文献(文档含中英文对照即英文原文和中文翻译)PavementHighway pavements are divided into two main categories: rigitand flexible.The wearing surfaceof a rigid pavement is usually constructed of Portland cement concrete such that it acts like a beam over any irregularities in the underlying supporting material.The wearing surface of flexible pavements, on the other hand, is usually constructed of bituminous material such that they remain in contact with the underlying material even when minor irregularities occur.Flexible pavements usually consist of a bituminous surface underlaid with a layer of granular material and a layer of a suitable mixture of coarse and fine materials.Coarse aggregatesFine aggregatesTraffic loads are transferred by the wearing surface to the underlying supporting materials through the interlocking of aggregates, the frictionaleffect of the granular materials, and the cohesion of the fine materials.Flexible pavements are further divided into three subgroups: high type, intermediate type, and low type. High-type pavements have wearing surfaces that adequately support the expected traffic load without visible distress due to fatigue and are not susceptible to weather conditions.Intermediate-type pavements have wearing surfaces that range from surface treated to those with qualities just below that of high-type pavements. Low-type pavements are used mainly for low-cost roads and have wearing surfaces that range from untreated to loose natural materials to surface-treated earth.✹The components of a flexible pavement include the subgradeor prepared roadbed, the subbase, basecourse, and the surface course (Fig.11.1).✹Upper surface courseMiddle surface courseLower surface courseThe performance of the pavement depends on the satisfactory performance of each component, which requires proper evaluation of the properties of each component separately.✹The subgrade is usually the natural material located along the horizontal alignment of the pavement and serves as the foundation of the pavement structure.✹The subgrademay also consist of a layer of selected borrow materials, well compacted to prescribedspecifications.✹Compacting plantCompaction deviceCompactnessIt may be necessary to treat the subgrade material to achieve certain strength properties required for the type of pavement being constructed.Located immediately above the subgrade, the subbase component consists of a superior quality to that which generally is used for subgrade construction. The requirements for subbase materials are usually given in terms of the gradation, plastic characteristics, and strength. When the quality of the subgrade material meets the requirements of the subbase material, the subbase component may be omitted.In cases where suitable subbase material is not readily available ,the available material can be treated with other materials to achieve the necessary properties. This process of treating soils to improve their engineering properties is know as stabilization.✹The base course lies immediately above the subbase. It is placed immediately above the subgrade if a subbase course is not used.✹This course usually consists of granular materials such as crushed stone, crushed or uncrushed.The specifications for base course materials usually include stricter requirements than those for subbase materials, particularly with respect to their plasticity, gradation, and strength.Materials that do not have the required properties can be used as base materials if they are properly stabilized with Portland cement, asphalt, or lime .In some cases, high-quality base course materials may also be treated with asphalt or Portland cement to improve the stiffness characteristics of heavy-duty pavementsThe surface course is the upper course of the road pavement and is constructed immediately above the base course. The surface course in flexible pavement usually consists of a mixture of mineral aggregates and asphaltic materials.It should be capable of withstanding high tire pressures, resisting the abrasive forces due to traffic, providing a skid-resistant driving surface, and preventing the penetration of surface water into the underlying layers.✹The thickness of the wearing surface can vary from 3 in. to more than 6 in.（inch，英寸，2.54cm）, depending on the expected traffic on the pavement.It was shown that the quality of the surface course of a flexible pavement depends on the mix design of the asphalt concrete used.✹Rigid highway pavements usually are constructed to carry heavy traffic loads, although they have been used for residential and local roads. Properly designed and constructed rigid pavements have long service lives and usually are less expensive to maintain than the flexible pavements.✹The Portland cement concrete commonly used for rigid pavements consists of Portland cement, coarse aggregate, fine aggregate, and water. Steel reinforcing rods may or may not be used, depending on the type of pavement being constructed.Rigid highway pavements be divided into three general type: plain concrete pavements, simply reinforced concrete pavements, and continuously reinforced concrete pavement. The definition of each pavement type is related to the amount of reinforcement used.Plain concrete pavement has no temperature steel or dowels for load transfer.However, steel tie bars are often used to provide a hingeeffect at longitudinal joints and to prevent the opening of these joints. Plain concrete pavements are used mainly on low-volume highways or when cement-stabilized soils are used as subbase.Joints are placed at relatively shorter distances (10 to 20 ft) than with the other types of concrete pavements to reduce the amount of cracking.In some case, the transverse joints of plain concrete pavements are skewed about 4 to 5 ft in plan, such that only one wheel of a vehicle passes through the joint at a time. This helps to provide a smoother ride.Simply reinforced concrete pavements have dowels for the transfer of traffic loads across joints, with these joints spaced at larger distances, ranging from 30 to 100 ft. Temperature steel is used throughout the slab, with the amount dependent on the length of the slab. Tie bars are also commonly used in longitudinal joints.Continuously reinforced concrete pavements have no transverse joints, except construction joints or expansion joints when they are necessary at specific positions, such as at bridges.These pavements have a relatively high percentage of steel, with the minimum usually at 0.6 percent of the cross section of the slab. They also contain tie bars across the longitudinal joints.h/2h/25~10cm填缝料 横向施工缝构造填缝料平缝加拉杆型Bituminous Surface CoursesThe bituminous surface course has to provide resistance to the effects of repeated loading by tyres and to the effects of the environment.✹In addition, it must offer adequate skid resistance in wet weather as well as comfortable vehicle ride. It must also be resistant to rutting and to cracking.✹It is also desirable that surface course is impermeable, except in the case of porous asphalt.Hot rolled asphalt (HRA) is a gapgraded material with less coarse aggregate. In fact it is essentially a bitumen/fine aggregate/filler mortar into which some coarse aggregate is placed.The mechanical propertiesare dominated by those of the mortar. This material has been extensively used as the wearing course on major road in the UK, though its use has recently declined as new materials have been introduced.✹It provides a durablelayer with good resistance to cracking and one which is relatively easy to compact. The coarse aggregate content is low (typically 30%) which results in the compacted mixture having a smooth surface. Accordingly, the skid resistance is inadequate and precoated chippings are rolled into the surface at the time of laying to correct this deficiency.In Scotland, HRA wearing course remains the preferred wearing course on trunk roads including motorway but，since 1999 thin surfacings have been the preferred option in England and Wales. Since 1999 in Northern Ireland, HRA wearing course and thin surfacings are the preferred permitted options.Porous asphalt (PA) is a uniformly graded material which is designed to provide large air voids so that water can drain to the verges within the layer thickness. If the wearing course is to be effective, the basecourse below must be waterproof and the PA must have the ability to retain its open textured properties with time.Thick binder films are required to resist water damage and ageing of the binder. In use, this material minimizes vehicle spray, provides a quiet ride and lower rolling resistance to traffic than dense mixtures.✹It is often specified for environmental reasons but stone mastic asphalt (SMA) and special thin surfacings are generally favoured in current UK practice.There have been high profile instances where a PA wearing course has failed early in its life. The Highways Agency does not recommend the use of a PA at traffic levels above 6000 commercial vehicles per day.✹Asphaltic concrete and dense bitumen macadam (DBM) are continuously graded mixtures similar in principle to the DBMs used in roadbases and basecourses but with smaller maximum particle sizes. Asphaltic concrete tends to have a slightlydenser grading and is used for road surfaces throughout the world with the excepting of the UK.✹It is more difficult to meet UK skid resistance Standards with DBMs than HRA, SMA or PA. This problem can be resolves by providing a separate surface treatment but doing so generally makes DBM economically unattractive.✹Stone mastic asphalt (SMA) material was pioneeredin Germany and Scandinavia and is now widely used in the UK. SMA has a coarse, aggregrate skeleton, like PA, but the voids are filled with a fine aggregate/filler /bitumen mortar.✹In mixtures using penetration grade bitumen , fibres are added to hold the bitumen within the mixture (to prevent “binder drainage”).Bitumen✹oil bitumen( earth oil)✹natural bitumen✹TarWhere a polymer modified bitumen is used, there is generally no need for fibres. SMA is a gap-graded material with good resistance to rutting and high durability. modified bitumen✹SBS✹SBR✹PE\EV A✹It differs from HRA in that the mortar is designed to just fill the voids in the coarse aggregate whereas, in HRA, coarse aggregate is introduced into the mortar and does not provide a continous stone matrix. The higher stone content HRAs ,however, are rather similar to SMA but are not wide used as wearing courses in the UK, being preferred for roadbase and basecourse construction.A variety of thin and what were called ultra thin surfacings (nowadays, the tendency is to use the term …thin surfacings‟ for both thin and ultra thin surfac ings ) have been introduced in recent years, principally as a result of development work concentrated in France.These materials vary in their detailed constituents but usually have an aggregate grading similar to SMA and often incorporate a polymer modified bitumen.They may be used over a high stiffness roadbase and basecourse or used for resurfacing of existing pavements. For heavy duty pavements (i .e those designed to have a useful life of forty years), the maintenance philosophy is one of minimum lane occupancy, which only allows time for replacement of the wearing course to these …long life‟ pavement structures. The new generation of thin surfacings allows this to be conveniently achieved.The various generic mixture types described above can be compared with respect to their mechanical properties and durability characteristics by reference to Fig.12.1. This shows, in principle, how low stone content HRA, asphaltic concrete, SMA and PA mixtures mobilize resistance to loading by traffic.Asphaltic concrete (Fig.12.1a)) presents something of a compromise when well designed, since the dense aggregate grading can offer good resistance to the shear stresses which cause rutting, while an adequate binder content will provide reasonable resistance to the tensile stresses which cause cracking.In general, the role of the aggregate dominates. DBMs tend to have less dense gradings and properties which, therefore, tend towards good rutting resistance andaway from good crack resistance.HRA (Fig.12.1b)) offers particularly good resistance to cracking through the binder rich mortar between the coarse aggregate particles. This also provides good durability but the lack of coarse aggregate content inhibits resistance to rutting.SMA and PA are shown in the same diagram ( Fig.c)) to emphasis the dominant role the coarse aggregate. In both case, well coated stone is used. In PA, the void space remains available for drainage of water, whilst in SMA, the space is occupied by a fine aggregate/ filler/ bitumen/ fibre mortar.Both materials offer good rutting resistance through the coarse aggregate content. The tensile strength of PA is low whilst that of SMA is probably adequate but little mechanical testing data have been reported to date.Drainage for Road and Airports✹Provision of adequate drainage is important factor in the location and geometric design of road and airports. Drainage facilities on any highway, street and airport should adequately provide for the flow of water away from the surface of the pavement to properly designed channels.Inadequate drainage will eventually result in serious damage to the structure.✹In addition, traffic may be slowed by accumulated water on the pavement, and accidents may occur as a result of hydroplaning and loss of visibility from splash and spray. The importance of adequate drainage is recognized in the amount of highway construction dollars allocated to drainage facilities. About25 percent of highway construction dollars are spent for erosion control anddrainage structures, such as culverts, bridges, channels, and ditches.✹Highway Drainage Structures✹One of the main concerns of the highway engineer is to provide an adequate size structure, such that the waterway opening is sufficiently large to discharge the expected flow of water.Inadequately sized structures can result in water impounding, which may lead to failure of the adjacent sections of the highway due to embankments being submerged in water for long periods.✹The two general categories of drainage structures are major and minor. Major structures are those with clear spans greater than 20 feet, whereas minor structures are those with clear spans of 20 feet or less .✹Major structures are usually large bridges, although multiple-span culverts may also be included in this class. Minor structures include small bridges and culverts.Emphasis is placed on selecting the span and vertical clearancerequirements for major structures. The bridge deck should be located above the high water mark .The clearance above the high water mark depends on whether the waterway is navigable ✹If the waterway is navigable, the clearance above the high water mark should allow the largest ship using the channel to pass underneath the bridge without colliding with the bridge deck. The clearance height, type, and spacing of piers also depend on the probability of ice jams and the extentto which floating logs and debris appear on the waterway during high water.✹An examination of the banks on either side of the waterway will indicate the location of the high water mark, since this is usually associated with signs of erosion and debris deposits. Local residents, who have lived near and observed the waterway during flood stages over a number of years, can also give reliable information on the location of the high water mark. Stream gauges that have been installed in the waterway for many years can also provide data that can be used to locate the high water mark.Minor structures, consisting of short-span bridges and culverts, are the predominant type of drainage structures on highways. Although openings for these structures are not designed to be adequate for the worst flood conditions, they shouldbe large enough to accommodate the flow conditions that might occur during the normal life expectancy of the structure.✹Provision should also be made for preventing clogging of the structure due to floating debris and large boulders rolling from the banks of steep channels.✹Culverts are made of different materials and in different shapes. Materials used to construct culverts include concrete（reinforced and unreinforced）, corrugated steel, and corrugatedaluminum. Other materials may also be used to line the interiorof the culvert to prevent corrosion and abrasionor to reduce hydraulic resistance. For example, asphaltic concrete may be used to line corrugated metal culverts. The different shapes normally used in culvert construction include circular, rectangular (box), elliptical, pipe arch, metal box, and arch.✹The drainage problem is increased in these areas primarily for two reasons: the impervious nature of the area creates a very high runoff; and there is little room for natural water courses. It is often necessary to collect the entire storm water into a system of pipes and transmit it over considerable distances before it can be loosed again as surface runoff. This collection and transmission further increase the problem, since all of the water must be collected with virtually no pending, thus eliminating any natural storage; and through increased velocity the peak runoffs are reached more quickly.Also, the shorter times of peaks cause the system to be more sensitive to short-duration,high intensive rainfall.Storm sewers,like culverts and bridges,are designed for storms of various intensity-return-period relationships, depending upon the economy and amount of ponding that can be tolerated.✹Airport Drainage✹The problem of providing proper drainage facilities for airports is similar in many ways to that of highways and streets. However, because of the large and relatively flat surface involved, the varying soil conditions, the absence of natural water courses and possible side ditches, and the greater concentration of discharge at the terminus of the construction area, some phases of the problem are more complex. For the average airport the over-all area to be drained is relatively large and an extensive drainage system is required. The magnitude of such a system makes it even more imperative that sound engineering principles based on all of the best available data be used to ensure the most economical design.Overdesigning of facilities results in excessive money investment with no return, and underdesigning can result in conditions hazardous to the air traffic using the airport. In order to ensure surfaces that are smooth, firm, stable, and reasonably free from flooding, it is necessary to provide a system which will do several things.It must collect and remove the surface water from the airport surfaces; intercept and remove surface water flowing toward the airport from adjacent areas; collect and remove any excessive subsurface water beneath the surface of the airport facilities and in many cases lower the ground-water table; and provide protection against erosion of the sloping areas.路面公路的路面被分为两类：刚性的和柔性的。
交通建设项目工程专业外文翻译外文文献英文文献.doc
土木工程学院交通工程专业中英文翻译Road Design专业：交通工程英文原文The Basics of a Good RoadWe have known how to build good roads for a long time. Archaeologists have found ancient Egyptian roadsthat carried blocks to the pyramids in 4600 BCE. Later,the Romans built an extensive road system, using the same principles we use today. Some of these roads are still in service.If you follow the basic concepts of road building, you will create a road that will last. The ten commandments of a good road are:（1）Get water away from the road（2）Build on a firm foundation（3）Use the best materials（4）Compact all layers properly（5）Design for traffic loads and volumes（6）Design for maintenance（7）Pave only when ready（8）Build from the bottom up（9）Protect your investment（10）Keep good records1．Get water away from the roadWe can’t overemphasize the importance of good drainage.Engineers estimate that at least 90% of a road’s problems can be related to excess water or to poor waterdrainage. Too much water in any laye r of a road’sstructure can weaken that layer, leading to failure.In the surface layer, water can cause cracks and potholes. In lower layers it undermines support, causing cracks and potholes. A common sign of water in an asphalt road surface is alligator cracking — an interconnected pattern of cracks forming small irregular shaped pieces that look like alligator skin. Edge cracking, frost heaves, and spring breakup of pavements also point to moisture problems.To prevent these problems remember that water:• flows downhill• needs to flow someplace• is a problem if it is not flowingEffective drainage systems divert, drain and dispose of water. To do this they use interceptor ditches and slopes,road crowns, and ditch and culvert systems.Divert —Interceptor ditches, located between the road and higher ground along the road, keep the water from reaching the roadway. These ditches must slope so they carry water away from the road.Drain —Creating a crown in the road so it is higher along the centerline than at the edges encourages water to flow off the road. Typically a paved crown should be 1⁄4" higher than the shoulder for each foot of width from the centerline to the edge. For gravel surfaces the crown should be 1⁄2" higher per foot of width. For this flow path to work, the road surface must be relativelywater tight. Road shoulders also must be sloped away from the road to continue carrying the flow away. Superelevations (banking) at the outside of curves will also help drainthe road surface.Dispose —A ditch and culvert system carries water away from the road structure. Ditches should be at least one foot lower than the bottom of the gravel road layer that drains the roadway. They must be kept clean and must be sloped to move water into natural drainage. If water stays in the ditches it can seep back into the road structure and undermine its strength. Ditches should also be protected from erosion by planting grass, or installing rock and other erosion control measures. Erosion can damage shoulders and ditches, clog culverts, undermine roadbeds, and contaminate nearby streams and lakes. Evaluate your ditch and culvert system twice a year to ensure that it works. In the fall, clean out leaves and branches that can block flow. In spring, check for and remove silts from plowing and any dead plant material left from the fall.2．Build on a firm foundationA road is only as good as its foundation. A highway wears out from the top down but falls apart from the bottom. The road base must carry the entire structure and the traffic that uses it.To make a firm foundation you may need to stabilize the roadbed with chemical stabilizers, large stone called breaker run, or geotextile fabric. When you run into conditions where you suspect that the native soil is unstable, work with an engineer to investigate the situation and design an appropriate solution.3．Use the best materialsWith all road materials you “pay now or pay later.” Inferior materials may require extensive maintenance throughout the road’s life. They may also force you to replace the road prematurely.Crushed aggregate is the best material for the base course. The sharp angles of thecrushed material interlock when they are compacted. This supports the pavement and traffic by transmitting the load from particle to particle. By contrast, rounded particles act like ballbearings, moving under loads.Angular particles are more stable than rounded particles.Asphalt and concrete pavement materials must be of the highest quality, designed for the conditions, obtained from established firms, and tested to ensure it meets specifications. 4．Compact all layersIn general, the more densely a material is compacted, the stronger it is. Compaction also shrinks or eliminates open spaces (voids) between particles. This means that less water can enter the structure. Water in soil can weaken the structure or lead to frost heaves. This is especially important for unsurfaced (gravel) roads. Use gravel which has a mix of sizes (well-graded aggregate) so smaller particles can fill the voids between larger ones. Goodcompaction of asphalt pavement lengthens its life.5．Design for traffic loads and volumesDesign for the highest anticipated load the road will carry. A road that has been designed only for cars will not stand up to trucks. One truck with 9 tons on a single rear axle does as much damage to a road as nearly 10,000 cars.Rural roads may carry log trucks, milk trucks, fire department pumper trucks, or construction equipment. If you don’t know what specific loads the road will carry, a good rule of thumb is to design for the largest piece of highway maintenance equipment that will be used on the road.A well-constructed and maintained asphalt road should last 20 years without major repairs orreconstruction. In designing a road, use traffic counts that project numbers and sizes of vehicles 20 years into the future. These are only projections, at best, but they will allow you to plan for traffic loadings through a road’s life.6．Design for maintenanceWithout maintenance a road will rapidly deteriorate and fail. Design your roads so they can be easily maintained. This means:• adequate ditches that can be cleaned regularly• culverts that are marked for easy locating in the spring• enough space for snow after it is plowed off the road• proper cross slopes for safety, maintenance and to avoid snow drifts• roadsi des that are planted or treated to prevent erosion• roadsides that can be mowed safelyA rule of thumb for adequate road width is to make it wide enough for a snowplow to pass another vehicle without leaving the travelled way.Mark culverts with a post so they can be located easily.7．Pave only when readyIt is not necessary to pave all your roads immediately. There is nothing wrong with a well-built and wellmaintained gravel road if traffic loads and volume do not require a paved surface. Three hundred vehicles per day is the recommended minimum to justify paving.Don’t assume that laying down asphalt will fix a gravel road that is failing. Before you pave, make sure you have an adequate crushed stone base that drains well and is properly compacted. The recommended minimum depth of crushed stone base is 10" depending on subgrade soils. A road paved only when it is ready will far outperform one that is constructed too quickly.8．Ê Build from the bottom upThis commandment may seem obvious, but it means that you shouldn’t top dress or resurface a road if the problem is in an underlying layer. Before you do any road improvement, locate the cause of any surface problems. Choose an improvement technique that will address the problem. This may mean recycling or removing all road materials down to the native soil and rebuilding everything. Doing any work that doesn’t solve the problem is a waste of money and effort.9．Ê Protect your investmentThe road system can be your municipality’s biggest investment. Just as a home needs painting or a new roof, a road must be maintained. Wisconsin’s severe climate requires more road maintenance than in milder places. Do these important maintenance activities: Surface —grade, shape, patch, seal cracks, control dust, remove snow and iceDrainage —clean and repair ditches and culverts; remove all excess materialRoadside —cut brush, trim trees and roadside plantings, control erosionTraffic service —clean and repair or replace signsDesign roads with adequate ditches so they can be maintained with a motor grader. Clean and grade ditches to maintain proper pitch and peak efficiency. After grading, remove all excess material from the shoulder.10．Keep good recordsYour maintenance will be more efficient with good records. Knowing the road’s construction, life, and repair history makes it much easier to plan and budget its future repairs. Records can also help you evaluate the effectiveness of the repair methods and materials you used.Good record keeping starts with an inventory of the system. It should include the history and surface condition of the roadway, identify and evaluate culverts and bridges, note ditch conditions, shoulders, signs, and such structures as retaining walls and guardrails.Update your inventory each year or when you repair or change a road section. A formal pavement management system can help use these records and plan and budget road improvements.ResourcesThe Basics of a Good Road#17649, UW-Madison, 15 min. videotape. Presents the Ten Commandments of a Good Road. Videotapes are loaned free through County Extension offices.Asphalt PASER Manual(39 pp), Concrete PASER Manual (48 pp), Gravel PASER Manual (32 pp). These booklets contain extensive photos and descriptions of road surfacesto help you understand types of distress conditions and their causes. A simple procedure for rating the condition helps you manage your pavements and plan repairs.Roadware, a computer program which stores and reports pavement condition information. Developed by the Transportation Information Center and enhanced by the Wisconsin Department of Transportation, it uses the PASER rating system to provide five-year cost budgets and roadway repair/reconstruction priority lists.Wisconsin Transportation Bulletin factsheets, available from the Transportation Information Center (T.I.C.).Road Drainage, No. 4. Describes drainage for roadways, shoulders, ditches, and culverts.Gravel Roads, No. 5. Discusses the characteristics of a gravel road and how to maintain one.Using Salt and Sand for Winter Road Maintenance,No. 6. Basic information and practical tips on how to use de-icing chemicals and sand.Culverts—Proper Use and Installation, No. 15. Selecting and sizing culverts, designing, installing and maintaining them.Geotextiles in Road Construction/Maintenance andErosion Control, No. 16. Definitions and common applications of geotextiles on roadways and for erosion control.T.I.C. workshops are offered at locations around the state.Crossroads,an 8-page quarterly newsletter published by the T.I.C. carries helpful articles, workshop information, and resource lists. For more information on any of these materials, contact the T.I.C. at 800/442-4615.中文译文一个良好的公路的基础长久以来我们已经掌握了如何铺设好一条道路的方法，考古学家发现在4600年古埃及使用建造金字塔的石块铺设道路，后来，罗马人使用同样的方法建立了一个庞大的道路系统，这种方法一直沿用到今天。
土木工程公路工程中英文对照外文翻译文献
(文档含英文原文和中文翻译) 中英文对照外文翻译外文翻译（译文）公路工程20世纪的初期，美国的大多数的街道和马路都是用泥土、砖块和松柏木材建造而成的。
由于只是为马匹、马车和步行建造的，这些马路通常得不到细心维护，而且很窄，根本就容纳不下汽车的通行。
随着汽车制造业的发展，在当地有关部门监管下的私立收费公路开始涌现出来。
截止到1921年，美国有了共计38.7万公里的公路。
他们中的很多都是采用19世纪苏格兰工程师托马斯•特尔福德和约翰•麦克亚当（碎石路面正是因为他们而得名的）所制定的规范，他们的标准强调了充分排水的重要性。
除此之外，根本就没有关于大小尺寸、重量限制以及商业标识的国家标准。
在第一次世界大战期间，全国的马路几乎完全被重型卡车破坏了。
当艾森豪威尔将军——在德国服役于美国陆军第一洲际车队——于1919年从德国归国时，他说道：“旧的车队让我开始考虑完善的双车道的公路，但是德国的高速公路让我看到了更宽阔的跨地域纽带可显示出的智慧。
”又经过了一次战争，联邦政府才开始行动起来来建设全国范围的高速公路体系。
第二次世界大战期间，对货车和新道路数量的需求大幅度上升。
战争证明了道路对于防御系统工作的重要性。
13%生产防御设备的工厂都是靠卡车来获得原材料，而且几乎其他所有的工厂半数以上的产品都由机动车来运送。
战争同样也暴露了这样一个现象，对公路的地方管制已经导致已经导致了众多令人混淆的设计标准。
甚至联邦政府和各州的公路都不遵循基本的标准。
一些州允许卡车载重量高达36000磅，但另一些却限制载重不可以超过7,000磅。
一项政府研究项目建议在全国建设一个总长度为33,920英里的国家公路系统。
不久之后，国会很快通过了《1944年联邦资助公路法案》，这项法案呼吁建立严格的、由中央控制的道路设计标准。
州际公路系统最终于1956年正式动工，它被誉为上个世纪最伟大的公共工程之一。
为了修建长达44000公里的公路、桥梁、隧道网，人们必须制定出数以百计的有针对性的特殊工程设计方案和问题解决方针。
交通工程学：12_CapacityWeaving
Capacity and level of service analysis for freeways and multilane highway高速公路和多车道公路的通行能力和服务水平分析Los A Los B Los CLos D Los E Los FLevel of service服务水平HCM2000Level of service (LOS) is a quality measure describing operational conditions within a traffic stream, generally in terms of such service measures as speed and travel time, freedom to maneuver, traffic interruptions, and comfort and convenienceHighway Capacity Manual 2000 The Committee on Highway Capacity and Quality of Service of the TRB⏹Part I: Overview⏹ 1. Introduction⏹ 2. Capacity and level-of-service concepts ⏹ 3. Applications⏹ 4. Decision making⏹ 5. Glossary⏹ 6. Symbols ⏹Part II: Concepts⏹7. Traffic flow parameters ⏹8. Traffic characteristics⏹9. Analytical proceduresoverview⏹10. Urban street concepts ⏹11. Pedestrian and bicycleconcepts⏹12. Highway concepts⏹13. Freeway concepts⏹14. Transit concepts⏹Part III: Methodologies⏹15. Urban streets⏹16. Signalized intersections⏹17. Unsignalized intersections⏹18. Pedestrians⏹19. Bicycles⏹20. Two-lane highways ⏹21. Multilane highways ⏹22. Freeway facilities ⏹23. Basic freewaysegments⏹24. Freeway weaving ⏹25. Ramps and rampjunctions⏹26. Interchange rampterminals⏹27. Transit⏹Part IV: Corridor and areawide analyses ⏹28. Assessment of multiple facilities⏹29. Corridor analysis⏹30. Areawide analysis⏹Part V: Simulation and other models⏹31. Simulation and other toolsComparison of LOSLevel of service Description AverageSpacingMetersAverageSpacingCarsLOS A Operation is not greatly influenced by others; at flowfree speed; lane changing, merging, and divergingmaneuvers are easy;14624LOS B Begin to respond to other vehicles; drivers must bemore vigilant in searching for gaps8915LOS C The presence of other vehicles begin to restrictmaneuverability; any significant blockage could leadto breakdown and queuing6210LOS D Speed begin to decline with increase flows;breakdowns can occur quickly in response to smallincreases in flow467LOS E Represents operation in the vicinity of capacity;maneuvering within the traffic stream is very difficult36 6LOS F Describes operation within the queue that formsupstream of a breakdown point; stop and goService flow rateService flow rate is the maximum flow rate that can be accommodated while maintaining a designed level of service8001300180022002400FFS 120km/h freewayv/c ratio⏹The ratio of current or projected demand flow to the capacity of the facility⏹Demand and capacity video exampleTypical rural and urban roadwayclassification Subcategory Rural UrbanFreeways Interstate freeways, otherfreeways, expresswaysprincipal arterials,orArterials MajorMinor arterials Collectors Major collectors, MinorcollectorsLocal roads Residential, Commercial,Industrial中国的道路体系⏹公路高速公路一级公路二级公路三级公路四级公路⏹城市道路快速路主干路次干路支路Basic freeway segment（高速公路基本段） HCM2000 video exampleBASE CONDITIONS FOR BASICFREEWAY SEGMENTS⏹Minimum lane widths of 3.6 m;⏹Minimum right-shoulder lateral clearance between the edge of the travel lane and⏹the nearest obstacle or object that influences traffic behavior of 1.8 m;⏹Minimum median lateral clearance of 0.6 m;⏹Traffic stream composed entirely of passenger cars;⏹Five or more lanes for one direction (in urban areas only);⏹Interchange spacing at 3 km or greater;⏹Level terrain, with grades no greater than 2 percent;⏹A driver population composed principally of regular users of the facility.Speed-flow curves for basic freeway segmentsDensity is used to define LOSTypes of analysis for basic freeway sections and multilane highways ⏹Operational analysis⏹Service flow rate and service volume analysis⏹Design analysis⏹Page 302Free-flow speed (FFS)⏹In practical terms, it is the average speed of the traffic stream when flow rates are less than 1000 veh/h/ln⏹In theory, it is the speed intercept when flow is “zero”on a calibrated speed-flow curveFactors affecting FFSAdjustment for lane widthHow to find LOS ⏹Determine free flow speed⏹Determine flow rate⏹Then you will find LOSDetermine flow rateDriver population factor⏹The values of fp range from 0.85 to 1.00.⏹In general, the analyst should select 1.00ExampleFind LOS for an existing four-lane freewayWeaving, merging, and diverging movements on freeways andmultilane highwaysWeaving, merging and divergingWeavingWeaving occurs when one movement must cross the path of another along a length of facility without the aid of signals or other control devices,with the exception of guide and/or warning signsMerging and diverging⏹Merging occurs when two separate traffic stream join to form a single stream⏹Diverging occurs when one traffic stream separates to form two separate trafficHow to judge a weaving section ⏹Weaving occurs when a merge is closely followed by a diverge⏹HCM 2000 defines the distance to be less than 2500 ft(762 m)Level of service criteria for weaving, merging and divergingMerge and diverge influence areasAnalysis of weaving areasHistory of weaving areas study I ⏹In 1960s, the Bureau of Public Roads specially collected 12 sets data for weaving study, formeda complex and iterative methodology⏹It was part of a study of freeway related methodologies in the late 1970s⏹In 1980, a set of interim analysis procedures was published by TRB, 1960s methodology and a new independent developed methodology were includedHistory of weaving areas study II ⏹In the early 1980s, a study was carried on to solve the difference between the two methodologies. A third method was produced⏹In 1985 HCM, 3 methodologies were judgmentally merged⏹Studies throughout the 1980s and 1990s found no common consensus emerging⏹HCQSC of TRB rejected a simulation based approach⏹The method of HCM 2000 is still a judgmental modification of earlier procedures。
道路通行英文作文
道路通行英文作文Driving on the road can be quite an adventure. You never know what kind of traffic you'll encounter or what obstacles might come your way. It's a constant game of dodging potholes and avoiding reckless drivers.The key to successful road travel is to always stay alert and focused. You have to be ready for anything that comes your way, whether it's a sudden stop or a pedestrian crossing the street without looking.One of the most frustrating things about driving on the road is dealing with traffic jams. It's like being stuck in a never-ending line that never seems to move. You just have to be patient and hope that things will start moving again soon.Of course, it's important to always follow the rules of the road. That means obeying speed limits, using your turn signals, and not driving under the influence. It's allabout keeping everyone safe while on the road.Sometimes, you might encounter road construction or detours that can throw off your travel plans. It's just another part of the road experience that you have to navigate through. You might have to take a different route or deal with a longer commute, but it's all part of the journey.At the end of the day, driving on the road is all about being prepared for the unexpected. You never know what might happen, so it's best to be ready for anything. And remember, it's not just about getting to your destination, but also enjoying the ride along the way.。
道路交通工程专业外文翻译外文文献英文文献
土木工程学院交通工程专业中英文翻译Road Design专业：交通工程英文原文The Basics of a Good RoadWe have known how to build good roads for a long time. Archaeologists have found ancient Egyptian roadsthat carried blocks to the pyramids in 4600 BCE. Later,the Romans built an extensive road system, using the same principles we use today. Some of these roads arestill in service.If you follow the basic concepts of road building, you will create a road that will last. The ten commandments of a good road are:（1）Get water away from the road（2）Build on a firm foundation（3）Use the best materials（4）Compact all layers properly（5）Design for traffic loads and volumes（6）Design for maintenance（7）Pave only when ready（8）Build from the bottom up（9）Protect your investment（10）Keep good records1．Get water away from the roadWe can’t overemphasize the importance of good drainage.Engineers estimate that at least 90% of a road’s problems can be related to excess water or to poor waterdrainage. Too much water in any laye r of a road’sstructure can weaken that layer, leading to failure.In the surface layer, water can cause cracks and potholes. In lower layers it undermines support, causing cracks and potholes. A common sign of water in an asphalt road surface is alligator cracking — an interconnected pattern of cracks forming small irregular shaped pieces that look like alligator skin. Edge cracking, frost heaves, and spring breakup of pavements also point to moisture problems.To prevent these problems remember that water:• flows downhill• needs to flow someplace• is a problem if it is not flowingEffective drainage systems divert, drain and dispose of water. To do this they use interceptor ditches and slopes,road crowns, and ditch and culvert systems.Divert —Interceptor ditches, located between the road and higher ground along the road, keep the water from reaching the roadway. These ditches must slope so they carry water away from the road.Drain —Creating a crown in the road so it is higher along the centerline than at the edges encourages water to flow off the road. Typically a paved crown should be 1⁄4" higher than the shoulder for each foot of width from the centerline to the edge. For gravel surfaces the crownshould be 1⁄2" higher per foot of width. For this flow path to work, the road surface must be relatively water tight. Road shoulders also must be sloped away from the road to continue carrying the flow away. Superelevations (banking) at the outside of curves will also help drainthe road surface.Dispose —A ditch and culvert system carries water away from the road structure. Ditches should be at least one foot lower than the bottom of the gravel road layer that drains the roadway. They must be kept clean and must be sloped to move water into natural drainage. If water stays in the ditches it can seep back into the road structure and undermine its strength. Ditches should also be protected from erosion by planting grass, or installing rock and other erosion control measures. Erosion can damage shoulders and ditches, clog culverts, undermine roadbeds, and contaminate nearby streams and lakes. Evaluate your ditch and culvert system twice a year to ensure that it works. In the fall, clean out leaves and branches that can block flow. In spring, check for and remove silts from plowing and any dead plant material left from the fall.2．Build on a firm foundationA road is only as good as its foundation. A highway wears out from the top down but falls apart from the bottom. The road base must carry the entire structure and the traffic that uses it.To make a firm foundation you may need to stabilize the roadbed with chemical stabilizers, large stone called breaker run, or geotextile fabric. When you run into conditions where you suspect that the native soil is unstable, work with an engineer to investigate the situation and design an appropriate solution.3．Use the best materialsWith all road materials you “pay now or pay later.” Inferior materials may require extensive maintenance throughout the road’s life. They may also force you to replace the road prematurely.Crushed aggregate is the best material for the base course. The sharp angles of thecrushed material interlock when they are compacted. This supports the pavement and traffic by transmitting the load from particle to particle. By contrast, rounded particles act like ballbearings, moving under loads.Angular particles are more stable than rounded particles.Asphalt and concrete pavement materials must be of the highest quality, designed forthe conditions, obtained from established firms, and tested to ensure it meets specifications.4．Compact all layersIn general, the more densely a material is compacted, the stronger it is. Compaction also shrinks or eliminates open spaces (voids) between particles. This means that less water can enter the structure. Water in soil can weaken the structure or lead to frost heaves. This is especially important for unsurfaced (gravel) roads. Use gravel which has a mix of sizes (well-graded aggregate) so smaller particles can fill the voids between larger ones. Goodcompaction of asphalt pavement lengthens its life.5．Design for traffic loads and volumesDesign for the highest anticipated load the road will carry. A road that has been designed only for cars will not stand up to trucks. One truck with 9 tons on a single rear axle does as much damage to a road as nearly 10,000 cars.Rural roads may carry log trucks, milk trucks, fire department pumper trucks, or construction equipment. If you don’t know what specific loads the road w ill carry, a good rule of thumb is to design for the largest piece of highway maintenance equipment that will be used on the road.A well-constructed and maintained asphalt road should last 20 years without major repairs or reconstruction. In designing a road, use traffic counts that project numbers and sizes of vehicles 20 years into the future. These are only projections, at best, but they will allow you to plan for traffic loadings through a road’s life.6．Design for maintenanceWithout maintenance a road will rapidly deteriorate and fail. Design your roads so they can be easily maintained. This means:• adequate ditches that can be cleaned regularly• culverts that are marked for easy locating in the spring• enough space for snow after it is plowed off the road• proper cross slopes for safety, maintenance and to avoid snow drifts• roadsi des that are planted or treated to prevent erosion• roadsides that can be mowed safelyA rule of thumb for adequate road width is to make it wide enough for a snowplow to pass another vehicle without leaving the travelled way.Mark culverts with a post so they can be located easily.7．Pave only when readyIt is not necessary to pave all your roads immediately. There is nothing wrong with a well-built and wellmaintained gravel road if traffic loads and volume do not require a paved surface. Three hundred vehicles per day is the recommended minimum to justify paving.Don’t assume that laying down asphalt will fix a gravel road that is failing. Before youpave, make sure you have an adequate crushed stone base that drains well and is properly compacted. The recommended minimum depth of crushed stone base is 10" depending on subgrade soils. A road paved only when it is ready will far outperform one that is constructed too quickly.8．Ê Build from the bottom upThis commandment may seem obvious, but it means that you shouldn’t top dress or resurface a road if the problem is in an underlying layer. Before you do any road improvement, locate the cause of any surface problems. Choose an improvement technique that will address the problem. This may mean recycling or removing all road materials down to the native soil and rebuilding everything. Doing any work that doesn’t solve the problem is a waste of money and effort.9．Ê Protec t your investmentThe road system can be your municipality’s biggest investment. Just as a home needs painting or a new roof, a road must be maintained. Wisconsin’s severe climate requires more road maintenance than in milder places. Do these important maintenance activities: Surface —grade, shape, patch, seal cracks, control dust, remove snow and iceDrainage —clean and repair ditches and culverts; remove all excess materialRoadside —cut brush, trim trees and roadside plantings, control erosionTraffic service —clean and repair or replace signsDesign roads with adequate ditches so they can be maintained with a motor grader. Clean and grade ditches to maintain proper pitch and peak efficiency. After grading, remove all excess material from the shoulder.10．Keep good recordsYour maintenance will be more efficient with good records. Knowing the road’s construction, life, and repair history makes it much easier to plan and budget its future repairs. Records can also help you evaluate the effectiveness of the repair methods and materials you used.Good record keeping starts with an inventory of the system. It should include the history and surface condition of the roadway, identify and evaluate culverts and bridges, note ditch conditions, shoulders, signs, and such structures as retaining walls and guardrails.Update your inventory each year or when you repair or change a road section. A formal pavement management system can help use these records and plan and budget road improvements.ResourcesThe Basics of a Good Road#17649, UW-Madison, 15 min. videotape. Presentsthe Ten Commandments of a Good Road. Videotapes are loaned free through County Extension offices.Asphalt PASER Manual(39 pp), Concrete PASER Manual (48 pp), Gravel PASERManual (32 pp). These booklets contain extensive photos and descriptions of road surfaces to help you understand types of distress conditions and their causes. A simple procedure for rating the condition helps you manage your pavements and plan repairs.Roadware, a computer program which stores and reports pavement conditioninformation. Developed by the Transportation Information Center and enhanced by the Wisconsin Department of Transportation, it uses the PASER rating system to providefive-year cost budgets and roadway repair/reconstruction priority lists.Wisconsin Transportation Bulletin factsheets, available from the Transportation Information Center (T.I.C.).Road Drainage, No. 4. Describes drainage for roadways, shoulders, ditches, and culverts.Gravel Roads, No. 5. Discusses the characteristics of a gravel road and how to maintain one.Using Salt and Sand for Winter Road Maintenance,No. 6. Basic information and practical tips on how to use de-icing chemicals and sand.Culverts—Proper Use and Installation, No. 15. Selecting and sizing culverts, designing, installing and maintaining them.Geotextiles in Road Construction/Maintenance andErosion Control, No. 16. Definitions and common applications of geotextiles onroadways and for erosion control.T.I.C. workshops are offered at locations around the state.Crossroads,an 8-page quarterly newsletter published by the T.I.C. carries helpfularticles, workshop information, and resource lists. For more information on any of these materials, contact the T.I.C. at 800/442-4615.中文译文一个良好的公路的基础长久以来我们已经掌握了如何铺设好一条道路的方法，考古学家发现在4600年古埃及使用建造金字塔的石块铺设道路，后来，罗马人使用同样的方法建立了一个庞大的道路系统，这种方法一直沿用到今天。
公路通行能力外文翻译文献
公路通行能力外文翻译文献(文档含中英文对照即英文原文和中文翻译)Highway Capacity And Levels of Service Capacity DefinedA generalized definition of capacity is: The capacity of any element of the highway system is the maximum number of vehicles which has a reasonable expectation of passing over that section (in either one or both directions) during a given time period under prevailing roadway and trafficconditions. A sampling of capacities for modern highway elements is as follows:Capacity in PassengerFacilityCars Freeways and expressways away from ramps and2000 weaving sections, per lane per hourTwo-Lane highways, total in both directions, per2000hourThree-lane highways, total in each direction, per2000hourTwelve-foot lane at signalized intersection, per hour1800of green signal time(no interference and idealprogression)In treating capacity，TRB Circular 212 divides freeways into components: basic freeway segments and those in the zone of influence of weaving areas and ramp junctions. Capacities of expressways，multilane highways，and two- and three-lane facilities also have the two components: basic and those in the zone of influence of intersections. Each of these is treated separately below.Speed-Volume-Capacity Relationships for BasicFreeway and Multilane Highway SegmentsA knowledge of the relationships among speed，volume，and capacity is basic to understanding the place of capacity in highway design and operation. Figurel3.1，which gives such a relationship for a single freeway or expressway lane, is used for illustrative purposes.If a lone vehicle travels along a traffic lane，the driver is free to proceed at the design speed. This situation is represented at the beginning of the appropriate curve at the upper left of Fig. 13.1. But as the number of vehicles in the lane increases, the driver's freedom to select speed is restricted. This restriction brings a progressive reduction in speed. For example，many observations have shown that，for a highway designed for 70 mph (113km/h)，when volume reaches 1900 passenger cars per hour，traffic is slowed to about 43 mph (69km/h). If volume increases further, the relatively stable normal-flow condition usually found at lower volumes is subject to breakdown. This zone of instability is shown by the shaded area on the right side of Fig. 13. 1. One possible consequence is that traffic flow will stabilize at about 2000 vehicles per hour at a velocity of 30 to 40 mph (48 to 64km/h) as shown by the curved solid line on Fig. 13. 1. Often，however , the quality of flow deteriorates and a substantial drop in velocity occurs; in extreme cases vehicles may come to a full stop. In this case the volume of flow quickly decreases as traffic proceeds under a condition known as …forced flow.‟ V olumes under forced flow are shown by the dashed curve at the bottom of Fig. 13. 1. Reading from that curve，it can be seenthat if the speed falls to 20 mph (32km/h)，the rate of flow will drop to 1700 vehicles per hour; at 10 mph （16km/h) the flow rate is only 1000;and,of course，if vehicles stop，the rate of flow is 0. The result of this reduction in flow rate is that following vehicles all must slow or stop，and the rate of flow falls to the levels shown. Even in those cases where the congestion lasts but a few seconds, additional vehicles are affected after the congestion at the original location has disappeared. A …shock wave’develops which moves along the traffic lane in the direction opposite to that of vehicle travel. Such waves have been observed several miles from the scene of the original point of congestion，with vehicles slowing or stopping and then resuming speed for no apparent reason whatsoever.Effects of the imposition of speed limits of 60, 50, and 40 mph are suggested by the dotted lines on Fig. 13. 1. A 55-mph (88km/h) curve could also be drawn midway between the 60 and 50 mph dotted curves to reflect the effects of the federally imposed 55-mph limit, but this is conjectural since the level of enforcement varies so widely.Vehicle spacing，or its reciprocal, traffic density, probably have the greatest effect on capacity since it generates the driver's feeling of freedom or constraint more than any other factor. Studies of drivers as they follow other vehicles indicate that the time required to reach a potential collision point，rather than vehicle separation，seems to control behavior. However，this time varies widely among drivers and situations. Field observations have recordedheadways (time between vehicles) ranging from 0. 5 to 2 sec, with an average of about 1. 5s.Thus，the calculated capacity of a traffic lane based on this 1. 5 s average, regardless of speed，will be 2400 vehicles per hour. But even under the best of conditions, occasional gaps in the traffic stream can be expected，so that such high flows are not common. Rather, as noted，they are nearer to 2000 passenger cars per hour.The ‘Level of Service’ ConceptAs indicated in the discussion of the relationships of speed, volume or density, and vehicle spacing, operating speed goes down and driver restrictions become greater as traffic volume increase. …Level of service‟ is commonly accepted as a measure of the restrictive effects of increased volume. Each segment of roadway can be rated at an appropriate level，A to F inclusive，to reflect its condition at the given demand or service volume. Level A represents almost ideal conditions; Level E is at capacity; Level F indicates forced flow.The two best measures for level of service for uninterrupted flow conditions are operating or travel speed and the radio of volume to capacity达到最大限度的广播，called the v/c ratio. For two- and three-lane roads sight distance is also important.Abbreviated descriptions of operating conditions for the various levels of service are as follows:Level A—Free flow; speed controlled by driver's desire，speed limits, orphysical roadway conditions.Level B—Stable flow; operating speeds beginning to be restricted; little or no restrictions on maneuverability from other vehicles.Level C—Stable flow; speeds and maneuverability more closely restricted.Level D—Approaches unstable flow; tolerable speeds can be maintained but temporary restrictions to flow cause substantial drops in speed. Little freedom to maneuver，comfort and convenience low.Level E—V olumes near capacity; speed typically in neighborhood of 30 mph (48km/h); flow unstable; stoppages of momentary duration. Ability to maneuver severely limited.Level F—Forced flow，low-operating speeds，volumes below capacity; queues formed.A third measure of level of service suggested in TRB Circular 212 is traffic density. This is，for a traffic lane，the average number of vehicles occupying a mile (1. 6km) of lane at a given instant. To illustrate，if the average speed is 50 mph，a vehicle is in a given mile for 72 s. If the lane carrying 800 vehicles per hour，average density is then 16 vehicles per mile ;spacing is 330 ft (100m)，center to center. The advantage of the density approach is that the various levels of service can be measured or portrayed in photographs.From: Clarkson H. Oglesby and R. Gary Hicks “Highwayengineering”, 1982公路通行能力和服务水平通行能力的定义道路通行能力的广义定义是：在繁忙的道路和交通条件下公路系统任何元素的通行能力是对在指定的时间通过一断面（一个或两个方向）的最大数量的车辆有一个合理的预期。
专业英语论文-如何提高城市道路通行能力
How to improve the city road traffic capacityAbstractWith the rapid development of science and technology and economy, the road construction of our country is getting larger and larger, the road traffic system has become more and more perfect. However, in our country, there are always some local traffic quality can not meet people's travel demand, traffic congestion not only affects people's travel time, but also affect people's mood. China is a country with a large population, is also a transit country. Because of the rapid growth of the number of vehicles in today's society, available roads resources become more limited. Due to the restriction of land and economic factors such as road construction, can not be unlimited. Therefore, improving the traffic capacity of the road is not only for the existing roads, which are essential for the new road construction.Keywords: the traffic capacity of the road traffic managementThe traffic capacity of the road is a road in a unit of time, capable of handling traffic flow. Road conditions, traffic conditions, control conditions and climate, temperature, heart and other factors can directly or indirectly affect the traffic capacity of roads. Because the basic element of road traffic is the human, vehicle, road, so the correct handling of the relationship between people, car, road these three aspects is the key to explore how to improve the city road traffic capacity.On the Wuhan City, in order to improve the city road traffic capacity, traffic infrastructure construction is increasing. New bridge over Yangtze River tarted construction, the third ring road traffic, rail transit line 1, put into operation...... Full speed city traffic construction to alleviate traffic congestion, enhance city functions, provides a basic guarantee for improving the traffic environment. But at the same time, along with the development of Wuhan City People's economic level, Wuhan City vehicle capacity sharply, the total has exceeded million motor vehicles, to enter the high-speed growth period. Due to a sharp rise in the number of motor vehicles, the traffic pressure center region continues to increase, the traffic congestion from time and space has been the trend of diffusion. Although the city public traffic service quality has improved, but the basic pattern of the bus as the theme has not been a fundamental change. Therefore, in order to improve the traffic efficiency, alleviate the situation of traffic congestion, through scientific planning, reasonable organization, tackling the problem, a multi pronged.Human act as protagonist in the city traffic ,and what can be done to improve the ability of city road traffic? First, for pedestrians on the road, walking on the road, we must obey the traffic rules. In real life, we often hear this argument -- China crossing the street. In Chinese street, you can often see such a crossing method, a group of people, no matter the red light green light, directly across the road. Pedestrians crossing the road affected the normal passage of vehicles, causing traffic jams. However, the pedestrian crossing the road not only affected the normal traffic of City Road, but also to the security of the hidden dangers. "China type cross the road" is not bad, but it is certainly a common. From a social psychological perspective, "China type cross the road" shows the herd effect. When it was discovered that red light running rarely punished, egoism consciousness will sing leading role. In fact, India and other countries there is a red light phenomenon, just friends to "divorce" China type, the "Chinese type cross the road" of concern. Of course, the red light in many countries is beneath contempt. Many people go through a red light, can give this reason: to cross the road, as a very important matter, then is not near the car, wear the past is 10 seconds, and the car for at least 1 minute. Two, some light is unreasonable. The original design of red light conversion, have failed to account for changes in road, the traffic flow? If the green light is only 10 seconds, but the road is wide, I don't run a red light who break? We have a problem in cultural psychology, that is the rules are not strictly in accordance with the rules to perform, it also makes the "not illegal, small irregularities" is popular in society. In the environment, people often not prefect rules. "China type cross the road" reflects the unruly manner in which we appear in the development process. "". Can only rely on the integrity of the national quality education, improve safety awareness education. Let the society formed by signal lamp etiquette, is a long-term process. In the street walking, perhaps one you think small change, can cause very big effect to the traffic capacity, so we should cultivate good moral accomplishment and the heart of literacy. For example, when we obey the traffic rules through the crosswalk, sometimes encountered such a situation, when you get to the sidewalk central, signal lamp sidewalk direction turned red, the roadway direction will turn green. At this time, some people will rely on their own have the priority right, he will neither fast nor slow through the crosswalk, and during this time, the vehicle will have to avoid pedestrians pass by, and in. If in this case, a little change, fast through the intersection, perhaps will not be blocked so many cars, so, not good for small.In order to improve the city road traffic capacity, motor vehicle driver and can do what? As a qualified driver, first of all should obey the traffic rules. A qualified driver, not only technically adept, is more important to have good driving habits and moral cultivation. So what is with good habits and moral self-cultivation? As a driver, not only should they be responsible for their own safety, also should be responsible for the safety of others. So do not open her car, not in spite of driving, not fatigue driving. In the driving process, should be strictly in accordance with the traffic signs andmarkings on road driving. On the road, we can often see such people, to show their ability, open car avail oneself of loopholes, stuck in traffic junctions, there is always someone forced gasser, should be for the behavior of these people, making the road more plugging, sometimes because of bitter dispute, serious or even cause traffic accident. Therefore, in order to improve the city road traffic capacity, but also for the sake of others and their own interests and security, driving on the road, so as not to cause contradiction, do better to stop for three minutes, do not get a second.For the drivers, especially the internship driver, choose the right road is conducive to the improvement of city road traffic capacity. Because in each city, according to a combination of factors to consider, there are different levels of road construction, such as: the fast lane, the main road, secondary road. The fast track vehicle traveling speed is high. As for different driver, because the driving technology and psychological factors, the performance of vehicles and other reasons, the driving speed is not so high, if such a car driving on the freeway, one is the driving safety can not be guaranteed, and because these low speed car now the fast lane, the other vehicles had to slow down so fast, not so fast, the capacity can be reduced, so, according to its own speed optional road to improve road capacity.In order to improve the traffic capacity of the road, there must be an overall plan. First of all to the regional land use, social economy, national economic development plan, regional or city master plan and other relevant background and planning have a very good understanding and mastering. According to the regional and city planning and traffic development objectives and requirements, making reference to foreign advanced experience of city traffic rules, combined with the characteristics of traffic development, local area and the city present situation, development trends, the use of advanced ideas and technology of traffic planning, through technical and economic comparison of full, forward-looking, scientific formulation and preparation, targeted, guidance and traffic facilities system planning and traffic operational countermeasures. For example, more pedestrian traffic, frequent traffic junctions, can according to need to set up the pedestrian bridge, can construct interchange bridge in vehicle flow very large crossroads, instead of the original indicator traffic signal lamp.In the city the road intersection, together with a mixed traffic flow consisting of motor vehicles, non motor vehicles and pedestrians, traffic congestion and traffic accident prone locations, there exist many cross traffic flow with the same plane shunting, intersection and conflict traffic behavior, become the bottleneck capacity of road network in the city. Therefore, crucial design of intersection is reasonable. In order to reduce conflict between point plane intersection and reduce the degree of conflict, in normal traffic flow without the use of regional settings appropriate right into the right Island, provisions of vehicle location, can be of different models, different direction, different velocity and different state of motion of pedestrian andtraffic flow guidance, isolation and control, specification vehicle, organize the orderly flow through the intersection of roads, maximize the resource utilization, provide a refuge place for pedestrian and bicycle.The island into four sidewalk pedestrians, the main crossing distance greatly reduced. It also reducing the exposure time of each pedestrian in the driveway, improve pedestrian safety, while improving the pedestrian psychological safety.Relative to the intersection channelization after, intersection channelized intersection without conflict, wider range, all kinds of vehicles in the intersection interlaced track area has a lot of uncertainty, so when there are turning vehicles, easily to other direction of vehicle impact, resulting in conflict, and even lead to traffic accident.According to the road vehicle parking casually, should fundamentally solve the problem, through the investigation of parking and parking, rational planning of parking spaces, parking problem.....When the traffic system formed in a city, it is important to manage and control problems properly. Duality of traffic management and control of social science and natural science, involves people, vehicles, road, environment. A wide range of complex content, including technology, management, administration, laws and regulations management, traffic safety education and training, traffic monitoring. For the morning and evening rush hour this can implement the peak work, it can reduce the traffic flow in a certain extent, ease the traffic pressure peak. At the intersection can be used in intelligent traffic signal control lamp, according to the road lane vehicle, automatic control release time and cycle.In order to improve the traffic capacity of the road, there is to reduce unnecessary or unreasonable travel, must achieve this point should be reasonable selected station passenger and freight station. Optimization of guest, freight transportation hub, logistics distribution center, transfer station, would reducing the concentration of total travel, travel and travel distance. Rational planning and layout of the primary and secondary school, take the nearest school; variable concentration of single center for the centre etc..At present, the road was blocked because of the quantity of the vehicles running on the road too much. In many cases, a car can only take 1 people, while a bus can take more than 20 people, compared with the transport efficiency is greatly increased, the road are greatly reduced, so it should be possible development time less resource consumption, less environmental pollution, high transport efficiency, transport mode. The priority development of public transport, public transport development from the aspects of policy support, financial, tax, improve the service level of public transit.The conditions of the city should actively the development of rail transportation, the traffic, pollution small, covers an area of metro rail transit passenger flow to meet the requirements of small city. As the public transport develop to a certain extent, service level reaches a certain height, it will attract more people to choose this kind of preferential access to public transport, at that time , the number of private car on the road will become less, that is, the city road traffic capacity would be improved.如何提高城市道路通行能力摘要随着科学技术和经济的飞速发展，我国道路建设的规模越来越大，道路交通系统也日趋完善。
道路通行能力
§3-1 高速公路基本路段通行能力
高速公路基本路段 是指主线上不受匝道附近车辆汇合、分离 以及交织运行影响的路段部分
基本路段的理想条件
(1) 3.75m≤ 车道宽度≤ (2) 侧向净宽≥ (3) 车流中全部为小客车 (4) 驾驶员均为经常行驶高速公路且技术熟练遵守交通法规者
§3－2 双车道公路路段通行能力
路段车流运行特性
理想条件（影响因素） P167表9-19、9-20对双车道公路影响最大是速度、车道宽 度、交通量的方向分布和车型构成。 服务水平 P167 表9-21 计算思路 双车道公路中任何一方向的车辆在行驶过程中，不仅受到同向 车辆的制约，还受到反向车流的影响。因此，对通行能力和服 务水平的计算要采用双向同时分析的思路。
基本通行能力 basic capacity
公路的某组成部分在理想的道路、交通、控制和环境条件下，一条车道的一 横断面上，不论服务水平如何，1h所能通过标准车辆的最大辆数(pcu)
→ 通常以高速公路上观测到的最大交通量为基准(理想、理论通行能力)
可能通行能力 possible capacity
公路的某组成部分在实际的道路、交通、控制及环境条件下，一条车道的一 横断面上，不论服务水平如何，1h所能通过的车辆的最大辆数(pcu) → 是现实条件道路上的最大交通量（实际通行能力）
20 2 0 0 .9 0 7 0 .6 2 1 .0 5 24 v2 e /hh 5
达到可能通行能力前可增加的交通量V＝2425-1800＝625veh/h (5) 求理想条件下之速度及密度
1800veh/h的V/C在(2)中已求出为。查图9-2得平均行程速度为 78km/h，远大于观测到的速度56km/h，这由于有大型车及非平原的重丘 地形所致。
土木工程(道桥方向)专业外文翻译—路(公路)
毕业设计（论文）外文资料翻译系别：土木系专业：土木工程（道桥方向）班级：工077姓名：学号：外文出处：Prof essional Englishon Ci vilE ngineering M echanics附件：1、外文原文；2、外文资料翻译译文。
1、外文原文（复印件）Theroad(highway)The road i s one k indof l inearconstruction used for travel. It i s made of the roadbed, the roadsurface,thebridge,theculvertandthetunnel.Inaddition,italsohasthecrossingof lines, theprotective project and the traffic engineeringand the route facility.Theroadbedisthebaseofroadsurface,roadshoulder,sideslope,sideditchfoundations.Itisstonematerialstructure,whichisdesignedacc ording toroute'splaneposition.Theroadbed,asthebaseoftravel,mustguaranteethatit hasthe enough intensity andthe stability thatcanpreventthew a terand other natural disaster from corroding.The road surface is the surface of road. It is sing le or complex structure built w ithmix ture. Theroadsurfacerequirebeingsmooth,havingenoughintensity,goodstabilityandanti-slipperyfunction.The quality of road surface directly affects the safe, comfort and the traffic.The route marking i s one k indof traffic safety facility painted by oil paint or m adeby theconcreteandtilesonhigh-level,lesshigh-typesurface.Itsfunctioniscoordinatingthesigntomaketheeffectivecontroltothetransportation,directingthevehicle sskiproadtravel,servingunimpededandthesafepurpose.Ourcountry’s r oadroutemarkinghasthelanemedian l ine,thetrafficlaneboundary,thecurbline,theparkingline,theconductioncurrentbelt,thepedestriancrossingline,thef ourcornerscentercircle,theparkingazimuthline.Theroutemarkinghasthecontinualsolidline,thebroken l ineand the arrow indicator and itscolor uses the w hiteor the yellow.Thearchofbridgeisthe structurewhichstridesoverrivers,mountainvalleyandchannel.Itismade g enerallyby steel rod, concrete andstone.Thetunnelisthecavewhichconnectsbothsidesoftheroad.Thetechniqueofthisconstructionisverycomplex,thecostofthe projectsishigherthancommonroad.However,itreducesthe drivingdistancebetweentwoplaces,enhancesthegradeofthetechnicalinbuildingtheroadandguaranteesthe cars can drive fast and safely, thus reduces the cost of transportation.The protective project i s to protect and consolidate the roadbed in order that i t can g uaranteetheintensity and the stability of the road, thus maintains the automobile to pass throughsafely.In order to g uaranteethat safe operation of the highway transportation, besides the highwayengineeringandthevehiclesperformance,itmusthavesometrafficsignal,routemarking,eachkindofdirector anddemonstratefacility.Thehighwaymarkingusescertainmarkanddrawsymbol,simplewordsandnumber,theninsta llsinthesuitableplacetoindicatethe front road's condition or theaccidentconditionincludingtheinformationalsign,thewarningsignal,theprohibitorysign,theroadsig n and soon.The road w hichJoin city, village and industry, mainly are used for the automobile and hascertaintechnicalstandardandthefacilitypathcanbecalledthehighway.“T hehighway”in C hinesei sthemodernview,butitwasnotexistedinoldday.Itgetsthenamefromthemeaningofbeingusedforthepublictraffic.Whe rearethe human,therearetheroad.Itis a truth.However,the roadis notthehighway.Ifwetalkthehistoryabouttheroad,theearliesthighwayisthatbuiltbytheoldEgyptiansformakingthepyra mid.NextisthestreetwhichbuiltbytheBabylonpeopleabout4000yearsago.Allthese are much earlier than our country.A bout 500B .C ., the Persian Empire road has l inked up East and West, and connected the road toC hina. It i s the earliest and longest S ilkR oad. 2500 y ears ag o, i t mightbe the g reatestroad .Theancient R omeEmpire’s r oadw asoncecelebrated;i t took R omeasthecenter, a llaroundbuilt29roads.Thereforeitcameoutonecommonsaying:everyroadleadstoRome.The road's construction i s the process to enhance technique and renew the building materials.Theearliestistheoldroad,itiseasytobuildbutitisalsotodestroy.Ifthereistoomuchwaterorcars,itwillbeuneven andevenbedestroyed.ThemacadamroadappearedintheEuropewhichoutbalancedtheearliestmudroad.Thenthebri ckroadappearedwhichwasearlierthanChina.Itwasonegreatbreachthatwemoldedbitumenonthemacadamroad.Fro mancienttimestothepresent,Chinahascourierstationandcourierroad,whilethefirstmoreadvanceroadwastheonetha tfromLongZhouinGangXitoZhenNanGuanin1906.The difference betweenR oad and pathThe path i s the project for each k indof vehicles and people to pass through. A ccordingto itsfunction,wecandivideitintotheurbanroad,theroad,thefactoriesandminespath,theforestroadand county road.The classification of roadFirst, according to administrative rank, i t includes national highway, province road, countyroadand the special road. Generally the national highway and province road are named main l ine; thecounty road i s named branch line.The national road i s the m a in l ineand has political and economy s ignificance, includingtheimportantnationaldefenseroadandtheroadcollectingourcapitalwithotherprovinces,autonomousregi onsandmunicipalities.Itisalsotheroadlinkstheeconomycenter,seaporthinge,factoryandimportant strategicplace. The highway striding over different provinces are built, protected andmanagedby the special org anizationsw hichare approved by the ministry of communications.The provincial road i s the main l inebuilt, protected, managedby the road manage department.Iti s full of political and economic sense to the w hole province.The sing le w ay four levels of roads can adapt below each day and nightmedium-duty truckvolumeoftraffic200.The county route is refers to has county -w ide ( county -level city ) politics,theeconom-icsignificance,connectsinthecountyandthecountythemaintownship(town),theprin-cipalcommoditiesproductionandthecollectionanddistributioncenterroad,aswellasdoesnotbelongtothefederalhig hway,provincialroad'scountybordertheroad.Thecoun-tyroutebythecounty,thecityroad Departmentresponsible for the w orkis responsibleto construct, the maintenance and the management.The tow nshiproad refers to mainly the road w hichfor the tow nship( tow n) thev i l la -g eeconomy,theculture, the administration serves, as w ell as does not belong to above t-hecountyroutebetweenroad's townshipandthetownshipandthe townshipandthe exte-riorcontactroad.Townshipisresponsible by the people's governmentto construct, the m-aintenanceand themanagement.The special-purpose road i s refers to feeds specially or mainly supplies the factoriesandmines,theforestregion,thefarm,the oilfield,the touristarea,themilitaryimportantplaceandsoonandtheexternalrelationsroad.Thespecial-purposeroadisresponsiblebythespecial-purpose unit toconstruct,themaintenanceandthemanagement.Mayalsoentrustthelocalroad departmenttoconstruct, the maintenance and the management.S econd, according to the use duty, the function and adapts the volume of traffic division.A ccordingto our country present "Highway engineering Technical standard" theroadaccordingto the use duty, the function and the adaptation volume of tra-fficdividesinto highway,arterialroad,second-class road, tertiary highway, four level of road five ranks:1 st, the highway to feed specially the automobile and should control the differencec-ompletelyrespectively tow ardthe dividing strip on roads travel the multiple highway.The four traffic lane highway s oughtto be able to adapt each k indof automobile reduce passengervehicle'syearmeandiurnalvolumeoftraffic25000~55000.Thesixtrafficlanehighwaysoughttobeabletoadapteachkindofautomobilereducepassengervehicle'syearmean diurnalvolumeoftraffic45000~80000.The eighttraffic lane highway s oughtto be able to adapt each k indof automobiler-educepassengervehicle'syearmeandiurnalvolumeoftraffic60000~100000.2 nd, the arterial road to supplythe automobile and mayaccording to need to control thedifferencerespectivelytowardthe dividingstriponroadstravelthemultiplehighway.The four traffic lane arterial roads oughtto be able to adapt each k indof automobilreducepassengervehicle'syearmeandiurnalvolumeoftraffic15000~30000.The six traffic lane arterial roads oughtto be able to adapt each k indof automobilereducepassengervehicle'syearmeandiurnalvolumeoftraffic25000~55000.3rd,thesecond-classroadtosupplytheautomobiletravelthetwo-lanehighway.Canadapteachdayandnights3000~7500medium-dutytruckvolumeoftrafficgenerally.4 rd, tertiaryhighway s to mainly supply the automobile travel the two-lane highway.Canadapteachdayandnights1000~4000medium-dutytruckvolumeoftrafficgenerally.The5,fourlevelsofroadstomainlysupplytheautomobiletravelthetwo-laneorthesingle-lanehighway.The two-lane four levels of roads canadapt below each day and nightmedium-dutytruckvolumeoftraffic1500.Highway engineeringincludes Highway planning location design and maintenance. B eforethedesignandconstructionofa newhighwayorhighwayimprovementcanbeundertakentheremintbegeneralplaningandconsiderationoffinancingA spartofgeneralplanningitisdecidedwhatthetrafficneedofthereawillbeforaconsiderableperiod,generally20years,andwhatconstructionwillmeetthoseneeds.Toassesstrafficneedsthehighwaye ngineercollectsandanalyzesinformationaboutthephysicalfeaturesofexistingfacilities,thevolume,distribution,an dcharacterofpresenttraffic,andthechangestobeexpectedinthesefactor.Thehighwayengineermust determine the most suitablelocation lay out, and capacity of the new route and structures. Frequently, a preliminary l ineor locationand several a l ternate routes are studied. The detailed design i s normally beg un only w henthe preferredlocation has been chosen.In selecting the best route, careful consideration i s g ivento the traffic requirements terrain tobetraversedvalueoflandneededfortheright-of-way.andestimatedcostofconstructionforthevariousplans.Thephotogrammetricmethod,whichmakesuse ofaerialphotographsisusedextensivelytoindicate the character of the terrain on la rg e projects w here i t is most economical. On small project,Financing considerations determine w hetherthe project can be carried out t\t one time or whetherconstructionmustbeinstageswitheachstageinitiatedasfundsbecomeavailable.Indecidingthebestmethodof financingthe work, the engineermakesan analysis of whomit willbenefit.Importanthighway s and streets benefit* in vary ingdegrees, three g roups* users ow nersof adjacent property andthe g eneralpublic.U sersof improved highway s benefit from decreased cost of transportation, g reater travelcomfort,increasedsafetyandsavingoftime.Theyalsoobtainrecreationalandeducationalbenefits.Ownersofab uttingoradjacentpropertymaybenefitfrombetteraccess,increasedpropertyvalue,moreeffectivepoliceandfireprot ection,improvedstreetparkinggreaterpedestriantrafficsafety,andtheuseofthestreet rig ht-of-w ay for the location of public utilities such as w a terl inesand sewers.Evaluation of various benefits from highway construction i s often difficult but i s a m ostimportantphaseofhighwayengineering.Somebenefitscanbemeasuredwithaccuracy,buttheevaluationofothersismorespeculative.Asaresultnumerousmethodsarcusedtofinanc econstruction,andmuchengineeringw orkmay heinvolved in selecting the bestprocedure.Environmental evaluation. The environmental impact of constructing highway s hasreceivedincreasedattentionandimportance.Manyprojectshavebeendelayedandnumerousotherscanceledbec auseotenvironmentalproblems.Theenvironmentalstudyorreportcoversmanyfactors,includingnoisegeneration, airpollutiondisturbanceofareastraverseddestructionofexisting housing andpossible a l ternateroutes.Highway engineersmust a l so assist in the acquisition of rig ht-of-w ay needed for new highwayfacilitiesAcquisitionofthelandrequiredforconstructionofexpresswaylendinginto the centralbusiness areas of cities has proved extremely difficult ithe public i s demanding that traffic engineersworkcloselywithcityplanners,architects,sociologistsandallgroupsinterestedinbeautificationandimprove mentofcitiestoassurethatexpresswaysextendinxthroughmetropolitanareasbebuiltonlyafter coordinated evaluation of a l lmajor questions, including the follow ing;( 1 ) Is sufficient a ttentionbeing paid -to beautification of the ex pressway itself? ( 2 ) Wouldachangeinlocationpreserve major natural beauties of the city? (3) Coulda depressed design helogicallysubstitutedforthosesectionswhereanelevatedexpresswayisproposed?(4)Canthegeneraldesignheimpro vedtoreducethenoisecreatedbylargevolumesoftraffic?(5)Aresomesectionsofthe city being isolatedby the proposed location?Detailed design. Detailed design of a highway project includes preparation of draw ingsorblueprintstobeusedforconstruction.Theseplansshow,forexample,thelocation,thedimensionsofsucheleme ntsasroudwaywidth*thefinajprofilefor(heroad,thelocationandtypeofdrainagefacilities, and the quantities of w orkinvolved, including earthworkand surfacing.In planning the g radingoperations the design engineer considers the ty pe of material tobeencounteredinexcavatingorincuttingawaythehighpointsalongtheprojectandhowthe rnaterialremovedcanbestbeutilisedforfillorforconstructingembankmentsacrosslow areaselsewhereontheproject.Forthistheengineermustanalyzethegradationandphysicalpropertiesofthesoil,determ inehowtheembankmentscanbestbecompacted,andcalculatethevolumeofearthworktobedone.Electroniccalculati ngproceduresarenowsometimesusedforthelaststep.Electronicequipmenthas alsospeededupmanyotherhighwayengineeringcalculations.Powerfulandhighlymobile earth moving machines have been developed TO permit rapid and economical operations., S e lection of the ty peand thickness of roudw ay surfacing to be constructed i s an importantpartofdesign.Thetypechosendependsuponthemaximumloadstobeaccommodated,thefrequencyofthese loadsandotherfactors.Forsome mures,trafficvolumemaybeso lowthatnosurfacingiseconomicallyjustifiedandnaturalsoilservesastheroadway.Astrafficincreases,asurfacingofsan dycluy,crushedslag,crushedstonecalichecrushedoystershells,oracombinationofthesemaybeapplied.Ifgravelisuse d,itusuallycontainssufficientclay andfinematerialtohelpstabilizethesurfacing.Gravel surfaces may be further stubilizedby application of calcium chloride, w hicha l so a ids incontrollingdust.AnothersurfacingiscomposedofPortlandcementandwatermixediutotheupperfewinchesofthesuhg radeandcompactedwithrollers.Thisprocedureforms A soil-cementbasethatcanbesurfacedwithbituminousmaterials.Roadwaysrocarrylargevolumes ofheavyvehiclesmustbecarefully designedand made of considerable thickness.M uchof highway engineeringi s devoted to the planingand construction of facilities to drainthehighwayorstreetandlocarrystreamsacrossthehighwayright-of-way.R emovalof surface w a terfrom the road or street i s know n a surface druiuage . It isaccomplishedbyconstructingtheroadsothatithasacrownandbyslopingtheshouldersandadjacentareassoastocontr oltheflowofwatereithertowardexistingnaturaldrainage,suchasopenditches,orintoastormdrainagesystemofcalehba sinsandundergroundpipes.Ifastormdrainagesystemisused,asitwouldbewithcitystreets,thedesignengineermustgivec onsiderationtotherntalareadrainingontothestreet,themaximumrateofrunoffexpected,thedurationofthedesignstor m,theamountofpondingallowableateachcarchbasin,andtheproposedspacingofthecatchbasinsalongthestreet.Fro mthisinformationthedesiredcapacityoftheindividualeatehbaxinandthesizeoftheundergroundpipingnetworkurcc alculated.Indesigningfacilitiestocarrystreamsunderthehighway theengineermustdeterminetheareato be drained the maximumprobableprecipitationoverthe drainage basin,thehighestex pectedrunoffrare.and then, using ( hit information, must calculate the required capacity of l li t: drainagestructure.Generally designs a remade adequate to accommodatenot only the la rgestflow ever recorded for thatlocation but the g reatestdischarge that might be expected under the most adverse conditions for ag iven number of years.Factor considered in calculating the expected flow through a culvert opening include size, length,andshapeoftheopening,roughnessofthewalls,shapeoftheentranceanddownstreamendoftheconduit, maxim um a l low able heightof w atera t the entrance, and w a terlevel a t theoutletM uchengineeringund construction w orkhas been done to provide rest stops a longmajorexpresswayroutes t especiallythenationalsystemofinterstatehighways.Thesefacilitiesmustbecarefullylo catedtopermiteasyandsafeexitandreturnaccesstothehighway.Manyunitshavebeenbuilt^sceniclocationsinforested areastopermitpicnicgroundsandwalkwaysthroughtheforest.These rest areas are especially beneficial to tho« e drivers traveling long distances w ithfewstops.. The control and reduction of noise a long busy routes, especially expressway s, has become animportantpartofhighwayengineering.Inmanycommunitieshighwallshavebeenhuiltalongeithersideoftheexpress way.Suchwallscanhecostlytoconstruct,hutcanproveverybeneficial,barrierscan reduce overall noise levels by over 50 %.Constructionoperations.Althoughmuchengineeringandplaningmustbedonepreliminarytoit,the actual construction i s normally the costliest part of making highway uudstreet improvements.W i l li t h e aw ardof a construction contract follow ingthe preparation of the detailed plansandspecifications t engineersgoontotheftiteandlayouttheproject.Aspartofthisstakingout.limitsofearthworkar e show n, location of drainage structures indicated, and profiles established.Heavy rollers are used to compact the soil or subgradebelow the roadway in order to eliminatelatersettlement.Pneumatictiredrollersandsheepsfootrollers(steelcylindersequippedwithnumerousshort steelteethorfeetJareoftenemployedforthisoperation.Vibratoryrollershavebeendevelopedandusedonsomeproject sinrecentyears.Onetypevibratesupto3400times/min,compactingtheunderlyingmaterial to an appreciabledepth.M a intenanceand operation. Highway maintenance consists of the repair and upkeep of surfacingandshoulders,bridgesanddrainagefacilities?signs,trafficcontroldevices,guardrails,trafficstripingonthep avement,retainingwalls,andside slopes. Additionaloperationsincludeicecontrol undsnowremoval,becauseitisvaluabletoknowwhysomehighwaydesignsgivebetterperformanceandprove less costly to maintain than others, engineerssupervising maintenance can offer valuableguidanceto design engineers. Consequently, maintenance and operation arc important parts ofhighwayengineering.2、外文资料翻译译文路（公路）公路是供汽车或其他车辆行驶的一种线形带状结构体。
公路路面毕业论文中英文资料外文翻译文献
公路路面中英文资料外文翻译文献PavementHighway pavements are divided into two main categories: rigitand flexible.The wearing surfaceof a rigid pavement is usually constructed of Portland cement concrete such that it acts like a beam over any irregularities in the underlying supporting material.The wearing surface of flexible pavements, on the other hand, is usually constructed of bituminous material such that they remain in contact with the underlying material even when minor irregularities occur.Flexible pavements usually consist of a bituminous surface underlaid with a layer of granular material and a layer of a suitable mixture of coarse and fine materials.Coarse aggregatesFine aggregatesTraffic loads are transferred by the wearing surface to the underlying supporting materials through the interlocking of aggregates, the frictionaleffect of the granular materials, and the cohesion of the fine materials.Flexible pavements are further divided into three subgroups: high type, intermediate type, and low type. High-type pavements have wearing surfaces that adequately support the expected traffic load without visible distress due to fatigue and are not susceptible to weather conditions.Intermediate-type pavements have wearing surfaces that range from surface treated to those with qualities just below that of high-type pavements. Low-type pavements are used mainly for low-cost roads and have wearing surfaces that range from untreated to loose natural materials to surface-treated earth.The components of a flexible pavement include the subgradeor preparedroadbed, the subbase, basecourse, and the surface course (Fig.11.1).✹Upper surface courseMiddle surface courseLower surface courseThe performance of the pavement depends on the satisfactory performance of each component, which requires proper evaluation of the properties of each component separately.✹The subgrade is usually the natural material located along the horizontal alignment of the pavement and serves as the foundation of the pavement structure.✹The subgrademay also consist of a layer of selected borrow materials, well compacted to prescribedspecifications.✹Compacting plantCompaction deviceCompactnessIt may be necessary to treat the subgrade material to achieve certain strength properties required for the type of pavement being constructed.Located immediately above the subgrade, the subbase component consists of a superior quality to that which generally is used for subgrade construction. The requirements for subbase materials are usually given in terms of the gradation, plastic characteristics, and strength. When the quality of the subgrade material meets the requirements of the subbase material, the subbase component may be omitted.In cases where suitable subbase material is not readily available ,the available material can be treated with other materials to achieve the necessary properties. This process of treating soils to improve their engineering properties is know as stabilization.✹The base course lies immediately above the subbase. It is placed immediately above the subgrade if a subbase course is not used.✹This course usually consists of granular materials such as crushed stone, crushed or uncrushed.The specifications for base course materials usually include stricter requirements than those for subbase materials, particularly with respect to their plasticity, gradation, and strength.Materials that do not have the required properties can be used as base materials if they are properly stabilized with Portland cement, asphalt, or lime .In some cases, high-quality base course materials may also be treated with asphalt or Portland cement to improve the stiffness characteristics of heavy-duty pavementsThe surface course is the upper course of the road pavement and is constructed immediately above the base course. The surface course in flexible pavement usually consists of a mixture of mineral aggregates and asphaltic materials.It should be capable of withstanding high tire pressures, resisting the abrasive forces due to traffic, providing a skid-resistant driving surface, and preventing thepenetration of surface water into the underlying layers.✹The thickness of the wearing surface can vary from 3 in. to more than 6 in.（inch，英寸，2.54cm）, depending on the expected traffic on the pavement.It was shown that the quality of the surface course of a flexible pavement depends on the mix design of the asphalt concrete used.✹Rigid highway pavements usually are constructed to carry heavy traffic loads, although they have been used for residential and local roads. Properly designed and constructed rigid pavements have long service lives and usually are less expensive to maintain than the flexible pavements.✹The Portland cement concrete commonly used for rigid pavements consists of Portland cement, coarse aggregate, fine aggregate, and water. Steel reinforcing rods may or may not be used, depending on the type of pavement being constructed.Rigid highway pavements be divided into three general type: plain concrete pavements, simply reinforced concrete pavements, and continuously reinforced concrete pavement. The definition of each pavement type is related to the amount of reinforcement used.Plain concrete pavement has no temperature steel or dowels for load transfer. However, steel tie bars are often used to provide a hingeeffect at longitudinal joints and to prevent the opening of these joints. Plain concrete pavements are used mainly on low-volume highways or when cement-stabilized soils are used as subbase.✹Joints are placed at relatively shorter distances (10 to 20 ft) than with the other types of concrete pavements to reduce the amount of cracking.In some case, the transverse joints of plain concrete pavements are skewed about 4 to 5 ft in plan, such that only one wheel of a vehicle passes through the joint at a time. This helps to provide a smoother ride.Simply reinforced concrete pavements have dowels for the transfer of traffic loads across joints, with these joints spaced at larger distances, ranging from 30 to 100 ft. Temperature steel is used throughout the slab, with the amount dependent on the length of the slab. Tie bars are also commonly used in longitudinal joints.h/2 h/25~10cm 填缝料横向施工缝构造Continuously reinforced concrete pavements have no transverse joints, except construction joints or expansion joints when they are necessary at specific positions, such as at bridges.These pavements have a relatively high percentage of steel, with the minimum usually at 0.6 percent of the cross section of the slab. They also contain tie bars across the longitudinal joints.Bituminous Surface CoursesThe bituminous surface course has to provide resistance to the effects of repeated loading by tyres and to the effects of the environment.✹ In addition, it must offer adequate skid resistance in wet weather as well ascomfortable vehicle ride. It must also be resistant to rutting and to cracking.✹ It is also desirable that surface course is impermeable, except in the case ofporous asphalt.Hot rolled asphalt (HRA) is a gapgraded material with less coarse aggregate. In fact it is essentially a bitumen/fine aggregate/filler mortar into which some coarse aggregate is placed.The mechanical propertiesare dominated by those of the mortar. This material has been extensively used as the wearing course on major road in the UK, though its use has recently declined as new materials have been introduced.✹ It provides a durablelayer with good resistance to cracking and one which isrelatively easy to compact. The coarse aggregate content is low (typically 30%) which results in the compacted mixture having a smooth surface. Accordingly, the skid resistance is inadequate and precoated chippings are rolled into the surface at the time of laying to correct this deficiency.In Scotland, HRA wearing course remains the preferred wearing course on trunk roads including motorway but ， since 1999 thin surfacings have been the preferred option in England and Wales. Since 1999 in Northern Ireland, HRA wearing course and thin surfacings are the preferred permitted options.Porous asphalt (PA) is a uniformly graded material which is designed to provide平缝加拉杆型large air voids so that water can drain to the verges within the layer thickness. If the wearing course is to be effective, the basecourse below must be waterproof and the PA must have the ability to retain its open textured properties with time.Thick binder films are required to resist water damage and ageing of the binder. In use, this material minimizes vehicle spray, provides a quiet ride and lower rolling resistance to traffic than dense mixtures.✹It is often specified for environmental reasons but stone mastic asphalt (SMA) and special thin surfacings are generally favoured in current UK practice.There have been high profile instances where a PA wearing course has failed early in its life. The Highways Agency does not recommend the use of a PA at traffic levels above 6000 commercial vehicles per day.✹Asphaltic concrete and dense bitumen macadam (DBM) are continuously graded mixtures similar in principle to the DBMs used in roadbases and basecourses but with smaller maximum particle sizes. Asphaltic concrete tends to have a slightlydenser grading and is used for road surfaces throughout the world with the excepting of the UK.✹It is more difficult to meet UK skid resistance Standards with DBMs than HRA, SMA or PA. This problem can be resolves by providing a separate surface treatment but doing so generally makes DBM economically unattractive.✹Stone mastic asphalt (SMA) material was pioneeredin Germany and Scandinavia and is now widely used in the UK. SMA has a coarse, aggregrate skeleton, like PA, but the voids are filled with a fine aggregate/filler /bitumen mortar.✹In mixtures using penetration grade bitumen , fibres are added to hold the bitumen within the mixture (to prevent “binder drainage”).Bitumen✹oil bitumen( earth oil)✹natural bitumen✹TarWhere a polymer modified bitumen is used, there is generally no need for fibres. SMA is a gap-graded material with good resistance to rutting and high durability. modified bitumen✹SBS✹SBR✹PE\EV A✹It differs from HRA in that the mortar is designed to just fill the voids in the coarse aggregate whereas, in HRA, coarse aggregate is introduced into the mortar and does not provide a continous stone matrix. The higher stone content HRAs ,however, are rather similar to SMA but are not wide used as wearing courses in the UK, being preferred for roadbase and basecourse construction.A variety of thin and what were called ultra thin surfacings (nowadays, the tendency is to use the term ‘thin surfacings’ for both thin and ultra thin surfacings )have been introduced in recent years, principally as a result of development work concentrated in France.These materials vary in their detailed constituents but usually have an aggregate grading similar to SMA and often incorporate a polymer modified bitumen.They may be used over a high stiffness roadbase and basecourse or used for resurfacing of existing pavements. For heavy duty pavements (i .e those designed to have a useful life of forty years), the maintenance philosophy is one of minimum lane occupancy, which only allows time for replacement of the wearing course to these ‘long life’ pavement structures. The new generation of thin s urfacings allows this to be conveniently achieved.The various generic mixture types described above can be compared with respect to their mechanical properties and durability characteristics by reference to Fig.12.1. This shows, in principle, how low stone content HRA, asphaltic concrete, SMA and PA mixtures mobilize resistance to loading by traffic.Asphaltic concrete (Fig.12.1a)) presents something of a compromise when well designed, since the dense aggregate grading can offer good resistance to the shear stresses which cause rutting, while an adequate binder content will provide reasonable resistance to the tensile stresses which cause cracking.In general, the role of the aggregate dominates. DBMs tend to have less dense gradings and properties which, therefore, tend towards good rutting resistance and away from good crack resistance.HRA (Fig.12.1b)) offers particularly good resistance to cracking through the binder rich mortar between the coarse aggregate particles. This also provides good durability but the lack of coarse aggregate content inhibits resistance to rutting.SMA and PA are shown in the same diagram ( Fig.c)) to emphasis the dominant role the coarse aggregate. In both case, well coated stone is used. In PA, the void space remains available for drainage of water, whilst in SMA, the space is occupied by a fine aggregate/ filler/ bitumen/ fibre mortar.Both materials offer good rutting resistance through the coarse aggregate content. The tensile strength of PA is low whilst that of SMA is probably adequate but little mechanical testing data have been reported to date.Drainage for Road and Airports✹Provision of adequate drainage is important factor in the location and geometric design of road and airports. Drainage facilities on any highway, street and airport should adequately provide for the flow of water away from the surface of the pavement to properly designed channels.Inadequate drainage will eventually result in serious damage to the structure.✹In addition, traffic may be slowed by accumulated water on the pavement, and accidents may occur as a result of hydroplaning and loss of visibility from splash and spray. The importance of adequate drainage is recognized in the amount of highway construction dollars allocated to drainage facilities. About25 percent of highway construction dollars are spent for erosion control anddrainage structures, such as culverts, bridges, channels, and ditches.✹Highway Drainage Structures✹One of the main concerns of the highway engineer is to provide an adequate size structure, such that the waterway opening is sufficiently large to discharge the expected flow of water.Inadequately sized structures can result in water impounding, which may lead to failure of the adjacent sections of the highway due to embankments being submerged in water for long periods.✹The two general categories of drainage structures are major and minor. Major structures are those with clear spans greater than 20 feet, whereas minor structures are those with clear spans of 20 feet or less .✹Major structures are usually large bridges, although multiple-span culverts may also be included in this class. Minor structures include small bridges and culverts.Emphasis is placed on selecting the span and vertical clearancerequirements for major structures. The bridge deck should be located above the high water mark .The clearance above the high water mark depends on whether the waterway is navigable ✹If the waterway is navigable, the clearance above the high water mark should allow the largest ship using the channel to pass underneath the bridge without colliding with the bridge deck. The clearance height, type, and spacing of piers also depend on the probability of ice jams and the extentto which floating logs and debris appear on the waterway during high water.✹An examination of the banks on either side of the waterway will indicate the location of the high water mark, since this is usually associated with signs of erosion and debris deposits. Local residents, who have lived near and observed the waterway during flood stages over a number of years, can also give reliable information on the location of the high water mark. Stream gauges that have been installed in the waterway for many years can also provide data that can be used to locate the high water mark.Minor structures, consisting of short-span bridges and culverts, are the predominant type of drainage structures on highways. Although openings for these structures are not designed to be adequate for the worst flood conditions, they should be large enough to accommodate the flow conditions that might occur during the normal life expectancy of the structure.✹Provision should also be made for preventing clogging of the structure due to floating debris and large boulders rolling from the banks of steep channels.✹Culverts are made of different materials and in different shapes. Materials used to construct culverts include concrete（reinforced and unreinforced）, corrugated steel, and corrugatedaluminum. Other materials may also be used to line the interiorof the culvert to prevent corrosion and abrasionor to reduce hydraulic resistance. For example, asphaltic concrete may be used to line corrugated metal culverts. The different shapes normally used in culvert construction include circular, rectangular (box), elliptical, pipe arch, metal box, and arch.✹The drainage problem is increased in these areas primarily for two reasons: the impervious nature of the area creates a very high runoff; and there is little room for natural water courses. It is often necessary to collect the entire storm water into a system of pipes and transmit it over considerable distances before it can be loosed again as surface runoff. This collection and transmission further increase the problem, since all of the water must be collected with virtually no pending, thus eliminating any natural storage; and through increased velocity the peak runoffs are reached more quickly.Also, the shorter times of peaks cause the system to be more sensitive to short-duration,high intensive rainfall.Storm sewers,like culverts and bridges,are designed for storms of various intensity-return-period relationships, depending uponthe economy and amount of ponding that can be tolerated.✹Airport Drainage✹The problem of providing proper drainage facilities for airports is similar in many ways to that of highways and streets. However, because of the large and relatively flat surface involved, the varying soil conditions, the absence of natural water courses and possible side ditches, and the greater concentration of discharge at the terminus of the construction area, some phases of the problem are more complex. For the average airport the over-all area to be drained is relatively large and an extensive drainage system is required. The magnitude of such a system makes it even more imperative that sound engineering principles based on all of the best available data be used to ensure the most economical design.Overdesigning of facilities results in excessive money investment with no return, and underdesigning can result in conditions hazardous to the air traffic using the airport. In order to ensure surfaces that are smooth, firm, stable, and reasonably free from flooding, it is necessary to provide a system which will do several things.It must collect and remove the surface water from the airport surfaces; intercept and remove surface water flowing toward the airport from adjacent areas; collect and remove any excessive subsurface water beneath the surface of the airport facilities and in many cases lower the ground-water table; and provide protection against erosion of the sloping areas.路面公路的路面被分为两类：刚性的和柔性的。
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公路通行能力外文翻译文献(文档含中英文对照即英文原文和中文翻译)Highway Capacity And Levels of Service Capacity DefinedA generalized definition of capacity is: The capacity of any element of the highway system is the maximum number of vehicles which has a reasonable expectation of passing over that section (in either one or both directions) during a given time period under prevailing roadway and trafficconditions. A sampling of capacities for modern highway elements is as follows:Capacity in PassengerFacilityCars Freeways and expressways away from ramps and2000 weaving sections, per lane per hourTwo-Lane highways, total in both directions, per2000hourThree-lane highways, total in each direction, per2000hourTwelve-foot lane at signalized intersection, per hour1800of green signal time(no interference and idealprogression)In treating capacity，TRB Circular 212 divides freeways into components: basic freeway segments and those in the zone of influence of weaving areas and ramp junctions. Capacities of expressways，multilane highways，and two- and three-lane facilities also have the two components: basic and those in the zone of influence of intersections. Each of these is treated separately below.Speed-Volume-Capacity Relationships for BasicFreeway and Multilane Highway SegmentsA knowledge of the relationships among speed，volume，and capacity is basic to understanding the place of capacity in highway design and operation. Figurel3.1，which gives such a relationship for a single freeway or expressway lane, is used for illustrative purposes.If a lone vehicle travels along a traffic lane，the driver is free to proceed at the design speed. This situation is represented at the beginning of the appropriate curve at the upper left of Fig. 13.1. But as the number of vehicles in the lane increases, the driver's freedom to select speed is restricted. This restriction brings a progressive reduction in speed. For example，many observations have shown that，for a highway designed for 70 mph (113km/h)，when volume reaches 1900 passenger cars per hour，traffic is slowed to about 43 mph (69km/h). If volume increases further, the relatively stable normal-flow condition usually found at lower volumes is subject to breakdown. This zone of instability is shown by the shaded area on the right side of Fig. 13. 1. One possible consequence is that traffic flow will stabilize at about 2000 vehicles per hour at a velocity of 30 to 40 mph (48 to 64km/h) as shown by the curved solid line on Fig. 13. 1. Often，however , the quality of flow deteriorates and a substantial drop in velocity occurs; in extreme cases vehicles may come to a full stop. In this case the volume of flow quickly decreases as traffic proceeds under a condition known as …forced flow.‟ V olumes under forced flow are shown by the dashed curve at the bottom of Fig. 13. 1. Reading from that curve，it can be seenthat if the speed falls to 20 mph (32km/h)，the rate of flow will drop to 1700 vehicles per hour; at 10 mph （16km/h) the flow rate is only 1000;and,of course，if vehicles stop，the rate of flow is 0. The result of this reduction in flow rate is that following vehicles all must slow or stop，and the rate of flow falls to the levels shown. Even in those cases where the congestion lasts but a few seconds, additional vehicles are affected after the congestion at the original location has disappeared. A …shock wave’develops which moves along the traffic lane in the direction opposite to that of vehicle travel. Such waves have been observed several miles from the scene of the original point of congestion，with vehicles slowing or stopping and then resuming speed for no apparent reason whatsoever.Effects of the imposition of speed limits of 60, 50, and 40 mph are suggested by the dotted lines on Fig. 13. 1. A 55-mph (88km/h) curve could also be drawn midway between the 60 and 50 mph dotted curves to reflect the effects of the federally imposed 55-mph limit, but this is conjectural since the level of enforcement varies so widely.Vehicle spacing，or its reciprocal, traffic density, probably have the greatest effect on capacity since it generates the driver's feeling of freedom or constraint more than any other factor. Studies of drivers as they follow other vehicles indicate that the time required to reach a potential collision point，rather than vehicle separation，seems to control behavior. However，this time varies widely among drivers and situations. Field observations have recordedheadways (time between vehicles) ranging from 0. 5 to 2 sec, with an average of about 1. 5s.Thus，the calculated capacity of a traffic lane based on this 1. 5 s average, regardless of speed，will be 2400 vehicles per hour. But even under the best of conditions, occasional gaps in the traffic stream can be expected，so that such high flows are not common. Rather, as noted，they are nearer to 2000 passenger cars per hour.The ‘Level of Service’ ConceptAs indicated in the discussion of the relationships of speed, volume or density, and vehicle spacing, operating speed goes down and driver restrictions become greater as traffic volume increase. …Level of service‟ is commonly accepted as a measure of the restrictive effects of increased volume. Each segment of roadway can be rated at an appropriate level，A to F inclusive，to reflect its condition at the given demand or service volume. Level A represents almost ideal conditions; Level E is at capacity; Level F indicates forced flow.The two best measures for level of service for uninterrupted flow conditions are operating or travel speed and the radio of volume to capacity达到最大限度的广播，called the v/c ratio. For two- and three-lane roads sight distance is also important.Abbreviated descriptions of operating conditions for the various levels of service are as follows:Level A—Free flow; speed controlled by driver's desire，speed limits, orphysical roadway conditions.Level B—Stable flow; operating speeds beginning to be restricted; little or no restrictions on maneuverability from other vehicles.Level C—Stable flow; speeds and maneuverability more closely restricted.Level D—Approaches unstable flow; tolerable speeds can be maintained but temporary restrictions to flow cause substantial drops in speed. Little freedom to maneuver，comfort and convenience low.Level E—V olumes near capacity; speed typically in neighborhood of 30 mph (48km/h); flow unstable; stoppages of momentary duration. Ability to maneuver severely limited.Level F—Forced flow，low-operating speeds，volumes below capacity; queues formed.A third measure of level of service suggested in TRB Circular 212 is traffic density. This is，for a traffic lane，the average number of vehicles occupying a mile (1. 6km) of lane at a given instant. To illustrate，if the average speed is 50 mph，a vehicle is in a given mile for 72 s. If the lane carrying 800 vehicles per hour，average density is then 16 vehicles per mile ;spacing is 330 ft (100m)，center to center. The advantage of the density approach is that the various levels of service can be measured or portrayed in photographs.From: Clarkson H. Oglesby and R. Gary Hicks “Highwayengineering”, 1982公路通行能力和服务水平通行能力的定义道路通行能力的广义定义是：在繁忙的道路和交通条件下公路系统任何元素的通行能力是对在指定的时间通过一断面（一个或两个方向）的最大数量的车辆有一个合理的预期。