软土路基外文翻译--论公路路基施工技术

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论公路路基施工技术1引言公路路基施工是整个公路施工工程的关键所在，稍有偏差，将给整个工程埋下质量隐患。

例如，在公路施工中常会遇到诸如软土路基，黄土路基等不良路基，如不加以特别处理，会引起填方路堤施工后沉降或不均匀沉陷，路面纵横坡变碎，平整度下降，导致行车颠簸等，严重影响公路的正常使用，造成大量的人力、物力、财力浪费。

因此，路基施工应根据施工当地地形、地质状况、公路等级、所在地区的气候、结合施工填挖方平衡等来选择施工方法。

2路基填压公路路基的强度和稳定性很大程度取决于路基填料的性质及其压实的程度。

从现有条件出发，改进填土要求和压实条件是保证路基质量经济有效的方法。

2.1路基填料现行《公路路基设计规范》（以下简称规范）规定了对路基填料的要求。

对路基填料的最小强度和最大粒径给了量化的标准，采用承载比实验（CBR）值表征路基土的强度，引入了路床的概念。

对上路床的填料提出了限制条件，高速公路和一级公路路面底以下0cm-30cm的路床填料，其CBR值应大于8，对下路床及下面的填土也给出相应的规定值。

2.2路基压实当前路基施工，普遍采用了大吨位的压路机，碾压效果有了明显的改善。

对于提高路基土的压实度起了很好的作用。

规范规定高速公路和一级公路路面底面以下80cm－150cm部分的上路堤其压实度必须≥95％，对其它等级公路当铺筑高级路面时，其压实度亦应按高速公路和一级公路的标准采用。

此外，还增加了对路堤基底的压实度不宜小于93％的规定。

随着我国高速公路的飞速发展，路基施工技术也取得了相当大的进步，对于特殊路基的处理技术也日渐成熟和完善。

（1）过湿地区路基的填压。

过湿土地基的填筑比较简单，一般采用填砂砾垫层和加铺土工格栅的方法，该方法简单易行，处理效果较好。

但路基的压实是相当困难的，规范对此作出了若干调整：一是压实度标准可根据试验资料确定或较表列数值降低2—3个百分点；二是对于天然稠度小于1.1，液限大于40，塑性指数大于18的粘质土，用于下路床及下路堤填料时，可采用规定的轻型压实标准；三是改善填料的性质，在土中掺加生石灰，通常可以获得预期的效果，也可采用新型吸水材料加固。

（2）黄土路基的压实。

与其他公路路基黏性土相比，黄土尤其易受水的侵害，是一种特殊的黏性土。

常将黄土路基划分为两类：非湿陷性黄土和湿陷性黄土。

其中，湿陷性黄土主要分布在我国中西部地区，其作为路堤填筑材料时，由于水浸湿后，本身结构被迅速破坏，应有强度减小，若施工不当则会发生很大的下沉量，引起路基失稳，特别是高路堤地段的填筑更是会引发一系列的工程病害。

因此，黄土路基的压实也应根据实际情况的不同合理选择。

①冲击压实：冲击压实处理地基的原理是用一定的冲击能量使土体里的水分扩散固结并挤密压实土体而达到加固土体的目的。

冲击压实技术只适合于浅层湿陷性及湿软性黄土地基的处理，且其有效影响深度一般不超过80cm，冲压遍数以30遍左右为宜。

在冲压施工的过程中应注意：保持最佳含水量；受冲击压实机的机型限制，被冲压的路基长度一般不应小于120m，宽度不宜小于15m；每一层冲压前，应先沿路基边沿冲压5遍左右，以减少在冲压过程中冲击能对路基的侧向挤压作用；用冲击压实机进行路堤边沿压实时速度应稍慢，否则，可能引起车身滑出路堤；冲压时应注意轮迹的连续性，特别是调头处，不要预留空白带而影响压实效果。

②强夯施工：又称动力固结法，是用起重机械将8t～40t夯锤起吊到6m～25m 高度后，自由落下，给地基以强大的冲击能量的夯击，使土中出现冲击波和冲击应力，迫使土体孔隙压缩，土体局部液化，在夯击点周围产生裂隙，形成良好的排水通道，孔隙水和气体逸出，使土粒重新排列，经时效压密达到固结，从而提高地基承载力，降低其压缩性的一种有效地基加固方法。

3路基排水水是影响路基强度和稳定性的一个重要因素，水的侵蚀会造成许多路基病害的。

同时，从环境保护和不损害当地农田水利设施考虑，必须做好路基排水，形成排水系统，并与地区排水规划相协调，防止因各种原因造成的水患，给路基、路面施工造成不必要的损失。

公路排水主要包括两个方面：一是地下排水，即减少地下水、农田排灌水对路基稳定性及其强度的影响；二是路表排水，除将路面、地面的水迅速排出之外，应最大限度地减少雨水对路基、路面质量的影响，减少因路表水排水不畅或路表水下渗对路基、路面结构和使用性能产生的损害。

地下水排水设计可以采用适当提高路基最小填土高度或在路基底部设置隔水垫层等办法。

在施工前开挖临时排水边沟，排除施工期地表水并降低地下水，同时在路基底部掺加低剂量石灰处理，设置40cm厚的稳定层等，可起到较好的效果。

路表排水设计，一是可以通过路面横坡、边沟、边沟急流槽等将路表水迅速排出路基以外。

二是设计中央分隔带纵向碎石盲沟、软式透水管及横向排水管将施工期进入中央分隔带的雨水及运营期中央分隔带的下渗水迅速排出路基之外。

三是设计泄水孔以迅速排除桥面水。

四是采用沥青封层、土路肩纵横向碎石盲沟或排水管将渗入路面面层的水引出路基之外。

路面渗水的排水设计，沿路面边缘设置由透水性填料集水沟、横向出水管和过滤织物组成的路面边缘排水系统，通过设置沥青封层、土路肩纵横向碎石盲沟和排水管，将渗入路面面层的水引出路基之外。

由于通过沥青面层下渗的水量有限，设计中应在每10m左右设置一道Ф5cm 横向排水管以确保路面下渗水的排除。

4路基防护路基防护主要有三个方面。

（1）坡面防护。

坡面防护的目的是防止地表水流的冲刷、坡面岩土的风化剥落以及与环境的协调。

通常措施是采用石砌圬工防护，混凝土预制块护坡多用在路堤边坡，连片的及带窗孔的护面墙，用于路堑边坡。

但由于石砌圬工及混凝土防护存在造价高、易破损等诸多问题。

现在，种草防护技术应用较为广泛，边坡较高则采用砌石框格种草防护，起到改善生态环境、美化景观和坡面防护的三重效果。

石砌圬工防护的使用仍较普遍，混凝土预制块护坡多用在路堤边坡，连片的及带窗孔的护面墙用于路堑边坡。

破裂的或易于风化破碎的岩石路堑边坡采用锚杆挂铁丝网或高强塑料网格喷浆或喷射混凝土以及喷射纤维混凝土防护也有较好的效果。

但考虑到石砌圬工及混凝土防护造价高、易破损等诸多问题，从环境保护的角度出发，建议大力推广既能改善生态环境又美化景观的种草防护技术。

（2）冲刷防护。

传统的方法是用砌石、抛石、铁丝石笼和挡土墙防护，改进后可以用高强土工格栅代替铁丝做石笼，用聚脂或聚胺脂类土工织物混凝土护坡模袋做成的护面板防护受水冲击的边坡，很能适应土体不均匀沉降。

（3）支挡防护。

挡土墙用于支挡防护目前仍占主要。

①石砌的重力式挡土墙多用于石料丰富、墙高较低、地基较好的场合；②钢筋混结构的悬臂式挡土墙、扶壁式挡土墙和板柱挡土墙其受力比较合理，墙身圬工体积小，也已广泛应用于公路路基的防护；③垛式挡土墙易于调整墙的高度，并采用预制构件拼装，是一种特殊形式的挡土墙。

On the road subgrade construction technology1 IntroductionRoadbed construction is the key to the highway construction project, the slightest error will lay the whole project quality risks. For example, the Central Standing Committee met in the highway construction such as soft soil roadbed, roadbed and other bad loess roadbed, if not special treatment, would lead to construction of the embankment fill or uneven settlement after settlement, the road becomes broken vertical and horizontal slope, roughness decreased, resulting in road bumps, etc., seriously affect the normal use of the highway, causing a lot of manpower, material and financial resources to waste. Therefore, construction of embankment construction should be based on local topography, geology, road grade, where the region's climate, combined with the construction of such fill and cut Fang Pingheng to select the construction method.2 roadbed fill pressureRoad subgrade strength and subgrade stability largely depends on the nature and degree of compaction. Starting from the existing conditions, requirements and compacted fill to improve conditions is to ensure the quality and cost-effective way to subgrade.2.1 subgradeThe existing "roadbed design specification" (hereinafter referred to as norms) provides for the embankment fill requirements. The minimum strength of the subgrade and the maximum size for a quantitative standard, using Bearing Ratio test (CBR) value of the strength of the subgrade soil characterization, the introduction of the concept of the road bed. Of fill material for road beds proposed restrictions, highway and a road surface at the end of the following 0cm-30cm road bed fill, the CBR value should be greater than 8, the next road on the bed and fill the following provisions also give the corresponding value.2.2 Subgrade compactionThe current roadbed construction, generally with a large tonnage of rollers, rolling effect has been significantly improved. For improving the degree of compaction of subgrade soil played a positive role. Specification of the underside of the highway and a road surface the following 80cm -150cm part of the road embankment compaction degree must ≥ 95%, when the paved road to the other senior level surface,its degree of compaction should also highway and a class road from the criterion used. In addition, it increased the degree of compaction of the embankment base of not less than 93% of the requirement. With the rapid development of highway roadbed construction technology has also made considerable progress, for special subgrade treatment technology has become mature and improve.(1) wet areas embankment filling pressure. Through wet soil filling the foundation is relatively simple, commonly used to fill gravel cushion and processing shop geogrid method is simple, the treatment effect is better. However, compaction of subgrade is very difficult to regulate a number of adjustments to this: First, the standard compaction test data can be determined according to or lower than the tabulated value of 2-3 percentage points; the second is for the natural consistency of less than 1.1, liquid limit greater than 40, plasticity index greater than 18 of the clayey soil, for the next road-bed and under the embankment, the light can be specified compaction standards; third is to improve the nature of filler, mixed with lime in the soil, can usually get the desired results, but also a new absorbent material can be reinforced.(2) loess subgrade compaction. And compared to other road subgrade clay, loess are particularly vulnerable to violations of water, is a special kind of clay. Loess roadbed will often be divided into two categories: non-loess and loess. Among them, the loess mainly in central and western regions, as embankment material, due to water soaked, their structure is rapidly destroyed, should reduce the intensity, improper construction will occur if large subsidence, causing embankment instability, especially high embankment filling the lot is a series of projects will lead to disease. Therefore, the loess subgrade compaction should be reasonable based on the actual situation of the different options.①impact compaction: impact compaction process is the foundation of the principle that a certain impact energy of water diffusion in soil consolidation and compaction of soil compaction to achieve the purpose of soil reinforcement. Impact compaction technique is only suitable for shallow and marshy nature of collapsible loess foundation treatment, and its effective impact on the depth of not more than 80cm, punch a few times to 30 times or so. In the stamping process of construction should be noted: to maintain the optimum moisture content; by impact compactor models limit the length of the embankment by the general press of not less than 120m, width of not less than 15m; before pressing each layer should be punching along the edge of the first five times around the base to reduce the impact energy in the process of stampingthe lateral compression of the embankment; with the impact of edge of embankment compaction pressure of real-time machine speed should be slower, or may cause the body slid off the embankment; Stamping should pay attention to the continuity of the tracks, especially at the U-turn, do not affect the reserved space with the compaction effect.② dynamic compaction of construction: also known as dynamic consolidation method is used to 8t ~ 40t crane lifting hammer to 6m ~ 25m height, free fall, to the foundation with a strong impact energy of tamping, so that shock waves appear in the soil and the impact of stress, forcing compressed soil porosity, soil partial liquefaction, resulting in tamping points around the crack, forming a good drainage channel, pore water and gas escape, so that soil particles rearrange, compaction achieved by the time of consolidation, which improve the bearing capacity, reduce the compression of an effective foundation reinforcement methods.3 subgrade drainageSubgrade strength and influence of water is an important factor in stability, water erosion can cause many diseases of the roadbed. Meanwhile, from the local environmental protection and water conservancy facilities, without prejudice to consideration, must be prepared subgrade drainage, the formation of drainage systems, and coordination with regional drainage plan to prevent flooding due to various causes, to the embankment, causing unnecessary road construction the loss.Highway drainage include two aspects: First, underground drainage, a reduction of groundwater, farmland irrigation discharge stability and strength of the impact of the roadbed; second road surface drainage, in addition to the road, the rapid discharge of ground water outside, should be the maximum limits to reduce water on the roadbed, road surface quality, reducing water drainage due to poor road surface or road surface water infiltration on the roadbed, pavement structure and the use of performance damage.Groundwater drainage design appropriate to improve the subgrade or embankment fill height minimum set impermeable bottom cushion and other methods. In the pre-construction excavation temporary drainage ditches, excluding the construction period and reduce the groundwater surface water, while the bottom of the embankment lime mixed with low-dose treatment, setting 40cm thick stable layer, can play a good effect. Road surface drainage design, one can cross the road slope, Ditch, Ditch jet slot so the road surface water quickly discharged outside the embankment. Second, the design of the median longitudinal gravel blind ditch, softwater pipe and lateral drains into the median of the construction period and operation period of rain in the median of the rapid discharge of water seepage under the embankment beyond. Third, the design of the deck scuppers to quickly rule out the water. Fourth, the use of asphalt sealing layer of soil to the gravel shoulder vertical and horizontal blind ditch or drain to infiltration of water leads to the road surface outside the embankment. Seepage of surface drainage design, set up by the water permeability along the side edge of the filling gullies, horizontal outlet pipe and filter fabric composed of the edge of the road drainage system, by setting the seal layer of asphalt, stone blind to the vertical and horizontal soil shoulder and drainage ditch , the infiltration of water leads to the road surface outside the embankment. As the infiltration through the asphalt surface layer of water is limited, the design should be in every 10m or so to set a Ф5cm horizontal drains to ensure that the road surface seepage exclusion.4 embankment protectionThere are three main protective embankment.(1) slope protection. Slope protection to prevent surface water erosion, peeling and weathering of rock slope and environmental coordination. Usually measures is the use of stone masonry protection, precast concrete block is used in embankment slope protection, and the contiguous retaining wall with apertures for cutting slope.However, stone masonry and concrete protection there is high cost, easily damaged, and many other issues. Now, grass protection technology is widely used, the higher slope grass is used masonry sash protection, play to improve the ecological environment, landscaping and slope protection of the triple effect. The use of stone masonry protection are still quite common, many precast concrete blocks used in the embankment slope, contiguous, and the retaining wall with apertures for cutting slope. Easily broken or weathered broken rock cutting slope using high-strength bolt hanging wire or plastic mesh and shotcrete or sprayed concrete, sprayed fiber reinforced concrete and has a good protective effect.However, considering the stone masonry and concrete protection, high cost, easily damaged, and many other issues, from environmental point of view, it is recommended to promote not only improve the ecological environment and beautify the landscape and grass protection technology.(2) scour protection. The traditional method is to use masonry, riprap, and wire gabion retaining wall protection, improved high-strength geogrid can do instead of stone cage wire with polyester or polyurethane type geotextile bags made of concrete slope protection mode water-retaining panel by the impact of slope protection, it is ableto adapt to uneven soil settlement.(3) retaining protection. Protection for retaining walls which still accounts for the major. ①the gravity retaining wall stone used for stone-rich, high-low walls, foundation a better occasion; ② reinforced concrete cantilever retaining wall structure, wall bulkhead and retaining the slab-column by reasonable force, small masonry walls, has also been widely used in highway embankment protection; ③ pile retaining wall is easy to adjust the height of the wall, and the use of prefabricated assembly, is a special form of retaining walls.。