Rock mass strength by rock mass classification
新东门码头砂泥岩互层边坡分类及坡率取值
2021年6月第6期总第583期水运工程Port & Waterway Engineering Jun. 2021No. 6 Serial No. 583新东门码头砂泥岩互层边坡分类及坡率取值田文丰，林锐，杨堉果，李剑伟（四川省交通勘察设计研究院有限公司，四川 成都610017）摘要：新东门码头堆场岩质边坡开挖工程量大，开挖坡率会对工程造价产生较大影响。
针对这一问题，在依据现有规范坡率取值的基础上，探索新的边坡坡率计算公式。
在对比单一岩性质量分类（定性、RMR 及BQ 定量）和坡率取值（分类取 值、破裂角）的基础上，创新地提出了单一岩性抗剪强度坡率取值、互层岩体等效BQ 质量分类、互层岩体加权厚度抗剪强度坡率取值等方法，现场验证效果较好。
得出结论：1）由抗剪强度坡率公式法计算的坡率可较好地利用岩体自身稳定、控制 边坡安全、优化工程量。
2）此方法可为无软弱外倾结构面、地下水不丰富、非顺层情况下类似互层岩体边坡质量分类、坡 率取值提供一种新思路。
关键词：岩质边坡；单一岩性；抗剪强度坡率法；互层岩体；等效BQ 质量分类；加权厚度抗剪强度坡率法中图分类号：U65文献标志码：A文章编号：1002-4972（2021）06-0238-07Classification of sand-mudstone interbedded slope and value ofslope ratio at Xindongmen wharfTIAN Wen-feng, LIN Rui, YANG Yu-guo, LI Jian-wei(Sichuan Communication Surveying & Design Institute Co., Chengdu 610017, China)Abstract : The amount of excavation works on the rock slope of the Xindongmen Wharf Yard is large, and theexcavation slope rate will have a greater impact on the project cost. In response to this problem, new slope ratiocalculation formulas are explored based on the existing standard slope ratio. Compared with single lithologic qualityclassification (qualitative, RMR and BQ quantitative) and slope ratio method (classified value and fracture angle), the methods are innovatively proposed, such as the value of the shear strength gradient of a single lithology, theequivalent BQ quality classification of interbedded rock mass, and weighted thickness shear strength slope ratiomethod. And the on-site verification effect is better. It is concluded that: 1) The slope ratio calculated by the formula method of shear strength slope ratio can make good use of rock mass self-stability, control slope safety, and optimizeengineering quantity. 2) This method can provide a new idea for the quality classification and slope rate selection ofsimilar interbedded rock mass slopes in the case of no weak outwardly inclined structural planes, insufficient groundwater, and non-stratified conditions.Keywords ： rock slope; single lithology; shear strength slope ratio method; interbedded rock mass; qualityclassification of equivalent BQ; weighted thickness shear strength slope ratio method四川山区工程建设过程中，出现了大量的由 不同岩性组成的人工开挖岩质边坡，开挖坡率对工程量、造价将产生直接影响。
Strength of Rock and Rock Mass
Strength of Rock and Rock MassDesigning with rocks and rock masses bears many similarities to techniques that have been developed for soils. There is however a number of major differences:(1)The scale effect is overwhelming in rocks. Rock strength varies widely with sample size. Atone end, we have the intact rock (homogenous, isotropic, solid, continuous with no obvious structural defects) which really exists only at the hand-specimen scale. At the other end is the rock mass that is heterogeneous and anisotropic carrying all the defects that is characteristic of the rock mass at the field scale. In the design of engineering structures in rock, the size of interest is determined by the size of the rock mass that carries the stresses that are imposed on it.(2)Rock has tensile strength. It may have substantial tensile strength at the intact rock scale, butmuch smaller at the scale of the rock mass. Even then only in exceptional circumstances can the rock mass be considered as a “tensionless” material. Intact ro ck fails in tension along planes that are perpendicular to maximum tension (or minimum compression) and not along shear planes as suggested by the Coulomb theory).(3)The effect of water on the rock mass is more complex.(a)Pore space in most intact rocks is very small and so is the permeability. The watercontained in the pore space is not necessarily free water. The truly free water existsonly in the rock mass, in fractures, where water may flow at high rates.(b)In contrast to soils, water is more compressible (by about one order of magnitude)than intact rock. The difference would be smaller when compared with thecompressibility of the rock mass (especially close to the free surface where loose rockcommonly found).Note that in the derivation of the effectivesmall. This is not so for rocksincreasing the grain-to grain contactsignificant degree. The assumption ofwater controls the way anstress (total stress) is distributedconditions, the effective stressconcept passes the whole externalin rock, because water is more include its effect separately as a “water force” rather than mix its effect with the rock response (as in the effective stress theory).(4)In compression, intact rock does not fail according to the Coulomb theory. It is true, that itsstrength increases with confining pressure, but at failure there is no evidence for theappearance of a shear fracture as predicted by the Coulomb theory. Furthermore the “envelope “ is usually nonlinear following a y 2=x type of parabolic law. Interestingly, shear fractures do form, but not at peak stress; they form as part of the collapse mechanism, usually quite late in the post-failure history.Strength of Intact RockIntact rock has both tensile and compressive strength, but the compressive to tensile strength ratio is quite high, about 20. In uniaxial tension, failure follows the maximum principal stress theory:σ3=T owhich would suggest that the other two principal stresses have no influence. At failure a fractureplane forms that is oriented perpendicular to the σ3(Figure 28) Note that the Coulomb theory would predict shear failure in uniaxial tension at 45-φ/2with σ3. There was a suggestion to combine theCoulomb theory with the maximum stress theory (the tension cutoff) which would predict the properorientation of the failure plane for both tension andcompression. Others would rather replace both witha y 2=x type of parabola (Figure 29). As discussedearlier, the shear fracture does not appear at point of failure, so that this aspect of the Coulomb theory is meaningless. In fact, there is little point in using theMohr’s diagram. In rock mechanics, failure conditions are more meaningfully presented in theσ3-σ1 space using a nonlinear function for strength. Although there are many variations of this function, the most popular one is due to Hoek and Brown (1980) which has the general form of σσσσσ1332f c c m s =++This is shown in Figure 30. H ere σc is the uniaxial compressive strength of the intact rock, m is aconstant (characteristic of the rock type) and s is arock mass parameter. s =1 for intact rock. Typicalvalues of the m parameter can be found in the first row of Table 1. The s parameter is significant only in extending the strength function to the strength ofthe rock mass. The same diagram is often used to define the safety factor for an existing state of stress (σ3,σ1):τσSafety Factor f =σσ11where both σ1 and σ1f are measured at the value of σ3Strength of the Rock MassThe strength of the rock mass is only a fraction of the strength of the intact strength. The reason for this is that failure in the rock mass is a combination of both intact rock strength and separation or sliding along discontinuities. The latter process usually dominate. Sliding ondiscontinuities occurs against the cohesional and/or frictional resistance along the discontinuity. The cohesional component is only a very small fraction of the cohesion of the intact rock.Table 1. Finding the parameters m and s from classification parameters.In designing with the rock mass, two different procedures are used. When a rock block is well defi ned, its stability is best evaluated through a standard “rigid -body” analysis technique. All the forces on the block are vector-summed and the resultant is resolved into tangential and normal components with respect to the sliding plane. The safety factor becomes the ratio of the available resistance to sliding to the tangential (driving) force. This is the technique used in slope stabilityanalysis. The second technique is stress rather than force-based. Here the stresses are evaluated (usually modeled through numerical procedures) and compared with available strength. The latter is expressed in terms of the Hoek and Brown rock mass strength function. This is where the s parameter becomes useful. s=1 for intact rock and s<1 for the rock mass. Essentially, what we are doing is simply to discount the intact rock strength. The difficult question is what value to assign to s? There is no test that will define this value. In theory, its is possible to do field tests of the rock mass, but it is expensive and not necessarily very reliable. Hoek and Brown however have compiled a list of s values depending on the rock type and the rock classification ratings.A simplified version of this is presented in Table 1. To make use of this Table, one needs only the rock type and one of the ratings from either the CSIR or the NGI classification. Ratings that are not listed will have to be interpolated. User’s of this Table are however warned that this approach is given here as a guide and its reliability is open to question. Nevertheless, the given s values are so small that they would tend to under rather than overestimate thestrength of the rock mass. Problems however could arise when failure occurs along a single weak discontinuity (slope stability), in which case the stress-based approach is obviously invalid.We are going to show how design engineering structures in rocks through two examples. One will use the rock mass design using the Hoek and Brown approximation for strength and the other the technique of applying the block theory to designing rock slopes.In earlier discussions, we have worked an examplewith rock mass classification. Now let us assumethat we are going to build a twin-tunnel roadsystem at some depth in the worked rock mass.The plan is two make two inverted-U shapedtunnels, each tunnel to be 3 m high and 4 m wide.The tunnels are to be separated by a pillar (rockleft in place), preferably no more than 4 m wide.The safety factor for the pillar should be 1.5 orbetter. The depth of siting for the roadway has notbeen established yet, but it could range anywherebetween 100 and 300 m, the deeper the better.Your job is to find the appropriate depth withinthis range. This is an example for pillar design.The loading condition is determined by assuming that the weight of the overlying rock mass, as shown in Figure 31, is distributed evenly across the width of the pillar at AA (this is not quite true, the stresses are usually higher at the tunnel perimeter than at the center, but the high safety factor should take care of this). You follow this procedure now:(1)Find the rock mass strength using your classification and the strength table give above.(2)Find the volume and the weight of the overlying rock using 100 m for depth (check if youhave a unit weight for the rock in the report).(3)Distribute the total weigh over the cross sectional area AA. This is the average vertical stresson the cross section(4)Formulate the safety factor asSfStrength Vertical Sress(5) Check the safety factor at 300 m(6) See if you can get an algebraic expression for the safety factor using h as a variable.(7) What is the story you are going to tell the boss?In the second example, we are going to examine the stability of a block of rock found on a slope. Although this is going to be a simple problem, it will still illustrate the procedure involved in analyzing rock slope stability. Pay particular attention how the effect of ground water is incorporated into the stability analysis. We use block analysis when we expect the block to slide on a single or a combination of discontinuities and we have pretty good control over the geometry. This means that we have good knowledge of the size and through this the weight of the block and the geometry of the slope. In the simple two-dimensional case, which we are to discuss, the geometry is simply the slope angle. The biggest problem is how to get a decent estimate of the resistance to slide. In this regard, conditions are similar to rock mass analysis, where we had to come up with an estimate of the rock mass strength. Again, we will have to use a lot of judgement. There are two ways to proceed. One is to accept the definition of shear resistance as in the Coulomb theory. This means that the discontinuity shear strength is made up of two components, a cohesion and a frictional resistance. The cohesion supposed to represent the strength of "solid rock bridges" that may exist at the base and will have to be sheared off to let the block move. This is the hardest part to estimate, because it may vary between zero and the strength of the solid rock (no bread at the base). Usually, it is a very small fraction of the solid strength. The frictional part is simply the normal force times the tangent of the friction angle. We use forces rather than stresses here and the resistance force according to the Coulomb specification becomes:Discontinuity shear strength Cohesive force N =+tan φThe Coulomb type of specification is useful only in the "back analysis" of slope failures. In theconsulting business, a common chore is toredesign slopes that have either failed orshowed signs of instability (tension crack at the back of the slope). In cases like this, thea good estimate of the frictionand find the value of theshear strength. Having this,force is practically impossible. discontinuity strengthby the same author who wasinvolved in constructing the NGIw a t e r w a t e r t h r u s tclassification (reference). The Coulomb theory proposes a linear law for discontinuity strength, the Barton specification advances a non-linear law:τσσφ=⎛⎝⎫⎭⎪+⎛⎝⎫⎭⎪nnbJRCJCStan log10Here stress rather than force units are used. σn and τ would refer to the average normal stress and the unit shear strength respectively. For comparison with the Coulomb specification, τ and σn are obtained by dividing the shear resistance force and the normal force by the area of contact. The Barton strength uses three material parameters: JRC (joint roughness coefficient), JCS (joint compressive strength) and φb (basic friction angle). JRC varies between 0 (very smooth, planar joint) and 20 (rough undulating surface). JCS is a fraction of the compressive strength of the rock. The compressive strength should be discounted depending on the condition of the rock walls on the two sides of the joint. Usually the surface is weathered and altered and may carry soft filling. In the latter case, the strength would be very small indeed. The basic friction angle is what we would normally call the friction angle determined on a flat surface rubbing against another flat surface of the same rock.Besides needing three parameters as opposed to Coulomb's two, the nonlinear strength is different from the Coulomb law that it has no strength at zero normal stress. Essentially, the Barton specification is defined in terms of a friction angle that is adjusted for joint roughness and the strength of rock.Being armed with some knowledge of discontinuity strength, we can now attempt to find the safety factor for the problem shown in Figure 32. We are looking at the stability of the dark-shaded mass of rock. There is the possibility of sliding down along joint plane sloping at angle α. First, we should establish the forces that act on this block of rock. Weight is an obvious one. The water forces are based on the assumption that water flows along the slide plane and perhaps along other joints or as in this case in a tension crack as well. If there was no tension crack, we would have an uplift force alone arising from the fact that water would normally flow in at the high-elevation end and flow out at the low elevation. The head of water at the intake and discharge points is zero. It would normally maximize between. Here we assume a triangular distribution, assuming that the maximum head occurs at midpoint and its value is one half of the elevation difference between intake and the discharge points. The uplift force itself is equal to the area of the pressure distribution diagram (light-shaded area) and acts perpendicular to the slide surface. With a tension crack, there could be a slope-parallel water thrust due to water accumulating in the tension crack. Its value would be calculated from the upper (small) light-shaded triangle. For this the maximum head would occur at the base, with the maximum head being equal to the elevation difference between the top and the bottom of the tension crack.With the loads now defined, we can go and get an estimate to the shear resistance that could develop along the sliding surface. Let us use the Coulomb specification. Furthermore, let us put in an extra little story here. Imagine that you are a consulting engineer who was called to this site, because the people below that rock block claim that the block almost came down on them during the last big rainfall. This story would justify the assumption that the safety factor is close to unity. So do this:(1)Assume that the elevation difference between the intake and discharge points is 20 m and theslope angle is 30︒. Find the weight of the block of rock (hint: turn it into a triangle to ease thepain of calculation) using a width of 1 m in the third direction. Assume 25 kN/m3 for the unit weight.(2)Compute the uplift force and the water thrust(3)Resolve all the forces into components, normal and parallel with the slide plane(4)Sum the parallel (tangential) forces to get the Driving Force(5)Sum the normal forces and get the total frictional resistance by multiplying it with tan φ (use30︒)(6)Define the cohesive force as unit cohesion times the total area of contact; the unit cohesionwill stay as a variable now(7)Add the cohesive force to the total frictional force(8)Formulate the safety factor, equate it with 1 and compute the friction angle.After this operation, you have all the strength parameters defined and are ready to redesign the slope. In practice, you would get rid of the water by drilling drainage holes to intersect and drain the slide plane. Assuming that the drainage works, do the last thing:(9) Find now the safety factor for the slope with the water effect gone! If it is greater than about 1.25, tell the people that the slope is safe as long as they have the drainage holes clean. Otherwise you would have to install and anchor system to increase the safety factor (changing the weight of the block by shaving it would result in a minor improvement only, you can try this analysis too.)。
原位直剪试验测试强风化岩体强度参数的数值模拟
原位直剪试验测试强风化岩体强度参数的数值模拟唐雪峰1，2（1．福建省地质工程勘察院福建福州350002；2．中国地质大学（北京）北京100083）［摘要］简述了某强风化岩的原位直剪试验，并采用数值模拟手段对试验进行模拟还原。
结果表明，模拟得到的土体强度参数与试验值较为接近，在一定程度上证明了数值计算方法的准确性。
而后对试样的应力变形特性进行了分析，试样剪应力云图大体呈现工字型分布，也即试样两端的剪应力较大，而中部的剪应力相对较小，试样在约束刚度较大的位置（如靠近铁质剪切盒）或具有一定凹角的接触面上（如剪切盒的边角处）存在明显的应力集中现象。
通过数值模拟计算，一方面可以更为全面地展示原位直剪试验结果，揭示在试验中所无法获取的信息，另一方面，模拟结论也能够跟试验成果互为佐证，以便将其可靠地推广应用到滑坡的防治研究中。
［关键词］原位直剪试验；强风化岩体；数值模拟；应力变形特性Numerical simulation of in －situ direct shear test on the strength parameters of strong －weathered rockAbstract ：The in －situ direct shear test of a strongly weathered rock is briefly described ，and the tests are reproduced by means of numeri-cal simulation．The results show that the simulated strength parameters are close to the test values ，which proves the accuracy of the numer-ical method to some extent．Then the stress and deformation characteristics of the specimen were analyzed ，the shear stress exhibits an"H"pattern ，that is ，the shear stress at the ends of the specimen is larger ，and shear stress in the central part of the specimen is relatively smal-ler．Obvious stress concentration can be observed where the constraint stiffness is larger （such as near the iron box ）or near the contact sur-face with a concave angle．Through numerical simulation ，on the one hand ，the direct shear test can be displayed more comprehensively so as to reveal the information that cannot be obtained in the test ；on the other hand ，the simulation results can also be mutually confirmed with the test results ，which helps to apply them to the research of landslide control more reliably．Key words ：field direct shear tests ，strong －weathered rock ，numerical simulation ，stress and deformation properties 基金项目：福建省科技重大专项（2016YZ0002－1），福建省科技创新平台建设（2014Y2007）作者简介：唐雪峰（1987－），女，福建莆田人，硕士，工程师，主要从事岩土工程勘察设计工作。
Practical estimates of rock mass strength
The criterion is purely empirical and hence there are no ‘correct’ ways to interpret the various relationships which can be derived. Under the circumstances, it is not surprising that there have been a few less than useful mutations and that some users have been confused by the alternative interpretations which have been published.
shear stresses. However, these relationships are
cumbersome and the original approach used by Hoek
and Brown [1] is more practical. In this approach,
equation (1) is used to generate a series of triaxial test
Dr Evert Hoek Evert Hoek Consulting Engineer Inc. 3034 Edgemont Boulevard P.O. Box 75516 North Vancouver, B.C. Canada V7R 4X1 Email: ehoek@
Lecture 2 Rock strengths and laboratory tests
ductility
Fig. 1 Failure classification
Section2 Compressive strength and influential factors
1. Definition of rock strength
In rock mechanics, failure stress is defined as rock strength.
The other factors are experimental approaches and physical conditions, such as specimen size, shape, friction between specimen and pressor head, rate of loading, etc.
will be high. Conversely, if rock has more mica(云母)、kaoline (高岭土), chlorite(绿泥石), talcum(滑石), rock compressive strength will be low.
The second interior factor： rock internal texture
porosity.
Fig.3 Strength and porosity dash line: compressive resistance solid line: tensile strength
The eighth interior factor: rock structure
Sedimentary rock has bedding(层理); Minerals are anisotropic. This anisotropic rock has different strength in different direction . Strength perpendicular to bedding plane is greater to the strength parallel to bedding plane, see table 2.
rock mech chap1
structural plane mechanics characters content： ： ①deformation characters and certain of parameters of structural plane under the compressive stress； ②shear strength feature and testing technique and methods of structural. distribution laws and measured theory and methods of in site stresses.
the use of all kinds of new technique 、methods and theory in rock mechanics. model 、 simulating experiment and in-situ detection technique of project body. Simulating experiment including numerical model simulating and physical model simulating is an important method to solve the rock mechanics and practical problems. Insitu detection technique could not only test the correction of analysis results of the body deformation and stability but also find question and take steps to solve in time.
Shock and Vibration
2
Shock and Vibration
that the key factors affecting the proper pillar width were the stopping span and depth. The relevant theory was verified by field tests.
Severe damage occurs frequently in mine pillars subjected to shear stresses. The empirical design charts or formulas for mine pillars are not applicable to orebodies under shear. In this paper, the failure process of pillars under shear stresses was investigated by numerical simulations using the rock failure process analysis (RFPA) 2D software. The numerical simulation results indicate that the strength of mine pillars and the corresponding failure mode vary with different width-to-height ratios and dip angles. With increasing dip angle, stress concentration first occurs at the intersection between the pillar and the roof, leading to formation of microcracks. Damage gradually develops from the surface to the core of the pillar. The damage process is tracked with acoustic emission monitoring. The study in this paper can provide an effective means for understanding the failure mechanism, planning, and design of mine pillars.
岩石动力特性试验规程
2
g)试验成果； h)安全保障。 5.3 试验前每个岩石试样应进行地质素描或拍照，试验后要对试样做破坏特征描述或拍照。 5.4 每个岩石试样宜做波速测定。 5.5 试验设备能标定的，应按规定标定；计量设备应按规定计量或校准。 5.6 试验数据记录与整理宜参照本规程附录 A。无特殊规定，计算结果应取三位有效数字。 5.7 试验结束应及时编制和提交试验报告，报告应有审核。
力方向上的波速。
图 1 岩样声波测试示意图
7.5 数据分析 7.5.1 波速计算
岩样声波波速按式（2）或（3）计算：
Cp=Ls/(tp-t0)
4
………………………(2)
Cs=Ls/(ts-t0)
………………………(3)
式中： Cp——纵波速度，单位为米每秒（m/s）； Cs——横波速度，单位为米每秒（m/s）； Ls ——岩样长度，单位为毫米（mm）； tp——纵波在仪器中显示的到时，精度至 0.1μs； ts——横波在仪器中显示的到时，精度至 0.1μs； t0——仪器系统的零延时。 7.5.2 数据统计 在整理同组岩样测试数据时，应给出每一个岩样的测值，计算值应取有效三位数字。 7.6 成果整理 岩样声速测试记录表如表A.1所示。岩样测试成果应给出纵波波速、横波波速、典型的波形图。
8.2.2 施密特锤使用要求 施密特锤的使用应符合下列的要求： a) 水平弹击时，弹击锤脱钩的瞬间，要求施密特锤的标准能量为 L 型: 0.735 J 和 N 型: 2.207 J； b) 弹击锤与弹击杆碰撞的瞬间，弹击拉簧应处于自由状态，此时弹击锤起跳点应相应于指针指示 刻度尺上“0”处； c) 施密特锤使用时的环境温度应为-4°C ~40°C； d) 施密特锤在检测前后，应在钢砧上作率定试验。施密特锤率定试验宜在干燥、室温为 5°C ~35°C 的条件下进行。率定时，钢砧应稳固地平放在刚度大的物体上。测定回弹值时，取连续向下弹 击三次的稳定回弹平均值。弹击杆应分四次旋转，每次旋转宜为 90°。弹击杆每旋转一次的率
巴西劈裂试验
ORIGINAL PAPERMixed-Mode Fracturing of Rocks Under Static and Cyclic LoadingN.Erarslan •D.J.WilliamsReceived:1April 2012/Accepted:19August 2012/Published online:2September 2012ÓSpringer-Verlag 2012Abstract Static diametrical compression tests conducted on inclined cracked chevron notched Brazilian disc (CCNBD)Brisbane tuff specimens showed that the not-ched cracks at the centre of the specimens opened (Mode I)up to 30°crack inclination angle (b ),whereas crack closure (Mode II)started for b [33°,and closure became more pronounced at even higher b of 45°and 70°.Both the experimental and numerical results showed that the crack initiation angle (h )was a function of the b .Scanning electron microscope (SEM)images showed that fatigue damage on cyclic loading of Brisbane tuff is strongly influenced by the failure of the matrix due to both inter-granular and transgranular fracturing.Keywords Mixed-mode fracturing ÁFRANC2D ÁCCNBD ÁCyclic loading ÁRock fatigue1IntroductionThe application and understanding of fracture mechanics has great importance in the analysis of the performance of rock structures.Rapid and violent failures of large-scale mining or civil engineering rock structures can cause sig-nificant safety hazards,material damage and interruption to mining or building activities.The fundamental questions in both mining and civil engineering relate to predicting the failure load of rock structures consisting of flaws and cracks,and to revealing the combination of load and flawgeometry that lead to failure.Rock discontinuities are also of major importance in structural geology and seismology.Rock fracture mechanics is one approach to recognising pre-failure rock mass behaviour,which may result in pre-dicting or preventing the potential for geotechnical and geological failure (Szwedzicki 2003).The prediction of the direction of crack propagation and orientation of fracture in a brittle rock becomes crucial,because,once a crack has opened,the state of stress in the vicinity of the crack tip is altered significantly.Failure mechanics (rock mechanics)and fracture mechanics seem to correlate with their investigations of rock breakage;however,there are differences between them.Rock failure mechanics is concerned with failure in a continuum sense,in which the rock or rock mass undergoes permanent damage,affecting its ability to sustain load.In contrast,fracture mechanics,sometimes called crack mechanics,is concerned with the individual crack or cracks.Moreover,existing failure criteria and theories,such as the well-known Coulomb criterion,often deal directly with fracture processes;however,they cannot be expected to deal with crack propagation in terms of the length of the crack or the direction of crack propagation.Fracture mechanics or,more specifically,linear elastic fracture mechanics (LEFM),has become well developed over the past 50years,as engineers have tried to under-stand the brittle failure of structures made of high-strength metal alloys (Rosmanith 1983).However,fracture mechanics was only applied to the study of rock fracturing in the 1980s (Whittaker et al.1992).Some past research on rock fracture mechanics has provided significant knowl-edge on tensile fracturing (Mode I fracturing;Atkinson et al.1982;Shetty et al.1985).Tensile fractures within rock can be generated in both tensile and compressive stress fields;therefore,they areN.Erarslan (&)ÁD.J.WilliamsGeotechnical Engineering Centre,School of Civil Engineering,The University of Queensland,St Lucia,Brisbane 4072,Australiae-mail:nazife.tiryaki@.auRock Mech Rock Eng (2013)46:1035–1052DOI 10.1007/s00603-012-0303-5very common.They include the vertical fractures caused in pillars in excavations due to the weight of the overburden,or fractures from the hydraulic stimulation of boreholes.Moreover,some researchers showed that shear loading (Mode II loading)of existing fractures was observed to initiate tensile fractures (Brace and Bombolakis 1963;Horii and Nemat-Nasser 1985).However,pre-existing cracks in rock and discontinuities in rock masses are sel-dom subjected to tensile loading (Mode I);rather,they are subjected to compressive,shear (Mode II)or mixed-mode loading (Mode I–II).Cracks or discontinuities in rocks are not subjected to just one type of loading.Some rock structures,such as bridge abutments,dam and road foundations,and tunnel walls,undergo both static and cyclic loading caused by,for example,vehicle-induced vibrations,drilling and blasting or traffic.This type of loading often causes rock to fail at a lower than expected stress.The design of such structures requires understanding of,and research on,rock mechan-ical parameters under various loading conditions.Thus,the objectives of this study were to:(1)investigate the change of failure load,fracturing mode and crack ini-tiation point with changing crack inclination angle (b ),which is defined as the angle between the diametral com-pressive load and the notched crack axis,under both static and cyclic loading;(2)compare fracturing modes under static and cyclic loading;and (3)analyse the applicability of one numerical tools based on the finite element method (FEM),which was implemented with classical fracture mechanics criteria applied to the crack propagation path under static diametral compressive loading using cracked chevron notched Brazilian disc (CCNBD)specimen geometry.2Theory of Crack Initiation Under Compressive and Mixed-Mode I–II Loading Cracks and/or discontinuities are common structural fea-tures of rock masses.LEFM is based on the stress intensity factor (SIF),K ,which quantifies the intensity of the stresssingularity at the crack tip.Fracture mechanics states that a crack will propagate when its stress intensity reaches a critical value,K C ,assuming that the crack tip is in a state of plane strain.The stress intensity factor depends on the fracture displacement modes and crack geometry.A crack can deform in three basic modes:Mode I,Mode II and Mode III.The classification of fracturing is based on the crack surface displacement or the crack tip loading (Lawn 1993;Whittaker et al.1992).Mode I,which is also called the opening (tensile)mode,is so called because the crack tip is subjected to a normal stress and the crack faces separate symmetrically with respect to the crack front,so that the displacements of the crack surfaces are perpen-dicular to the crack plane (see Fig.1).The crack carries no shear traction and no shear displacement is visible.Mode II is the edge sliding (or in-plane shearing)mode,where the crack tip is subjected to an in-plane shear stress and the crack faces slide relative to each other so that the dis-placements of the crack surfaces are in the crack plane and are perpendicular to the crack front (see Fig.1).Mode III is the tearing mode,as the crack tip is subjected to an out-of-plane shear stress.The crack faces move relative to each other so that the displacements of the crack surfaces are in the crack plane,but are parallel to the crack front (see Fig.1).The International Society for Rock Mechanics (ISRM)has suggested two methods to determine the Mode I frac-ture toughness using a core-based specimen (Ouchterlony 1988;ISRM 1995,while several other methods have been proposed in the literature (Chong and Kuruppu 1984;Guo et al.1993).For the determination of Mode II fracture toughness,several experimental methods have been pro-posed in the literature (Jumikis 1979;Chang et al.2002;Ingraffea 1981;Backer 2004;Rao et al.2003;Hasanpour and Choupani 2009).The classical mixed-mode fracture criteria are incapable of predicting Mode II fracture toughness and,at present,there is no ISRM-suggested method for determining this toughness value.Many of the currently available methods used to measure the K IIC of rocks are based on the application of a pure,shear loading to the specimen,regardless of the fracture pattern,whichisFig.1Three fracture modes and corresponding crack surface displacements1036N.Erarslan,D.J.Williamswhy the fracturing of rocks under mixed-mode loading has attracted more attention in recent years(Chang et al.2002; Rao et al.2003;Al-Shayea2005;Ayatollahi and Aliha 2007).Various criteria have been suggested in the literature to explain crack initiation and propagation under mixed-mode I–II loading(Erdogan and Sih1976;Hussain and Pu 1974).For practical applications,the three fundamental fracture criteria of maximum tangential stress(Erdogan and Sih1976),maximum energy release rate(Hussain and Pu1974)and minimum strain energy density(Hussain and Pu1974)appear to be the most commonly employed.In general,the angle of fracture initiation and the frac-ture envelopes predicted by the different fracture criteria are in close agreement with each other,even though they are based on different fracture parameters and assumptions. They have been used for crack initiation and propagation under pure Mode I and Mode II loading.When they are used to study the crack initiation under compressive load-ing,the problem is more complicated.It has been postu-lated that crack initiation under compressive loading results from the crack tip local tensile stresses(Griffith1924). Crack initiation,propagation and specimen failure do not occur at the same time;rather,each separately forms a particular fracture process.However,the crack initiation from a pre-existing crack tip,called the primary crack,does not have to lead to failure,since this initial crack propa-gation may be arrested at some stress level.With increas-ing load,secondary cracks develop and propagate until they reach the boundary,leading tofinal failure,or until they act as a ligament between primary cracks to cause a final failure plane.The sliding crack model wasfirst pro-posed as a mechanism to study the non-elastic dilation of rocks under compressive loading(Brace and Bombolakis 1963).The model contains an initial crack that is oriented at an angle with respect to the compressive load,and a pair of curved tensile cracks that are oriented at an angle to the initial crack.According to the model,tensile cracks are caused by the sliding of the initial crack under compressive loading.An exact analytical solution of the stressfield to the sliding crack model was given by(Horii and Nemat-Nasser1985).With this solution,it was accepted that the critical orientation of a crack was inclined to the direction parallel to the major principal stress.Mixed-mode I–II fracture problems under compressive loading are shown to be more complicated than,and also quite different from,those under tension.In general,it is accepted that tensile cracks grow initially at an angle with respect to the direction of the compressive stress,and then rapidly grow in the direction of the compressive stress (Al-Shayea2005;Hoek and Bieniawski1965;Li et al. 2005).Relatively few published results are available regarding experimental work on mixed-mode I–II fractur-ing in rocks.There are also few published results on the fracture toughness under mixed-mode I–II loading(Chong and Kuruppu1984;Al-Shayea2005;Ayatollahi and Aliha 2007;Barker1977;Awaji and Sato1978;Huang and Wang1985;Chen1990).In general,it has been found that the full range of mixed-mode loading conditions,including pure Mode I and pure Mode II loading,could be created using an inclined crack with inclination angles(b)between0°and90°. Another study investigated mixed-mode fracturing in sandstone specimens under three-point bending(Li et al. 2005).They found that crack initiation did not start from the pre-existing notched crack under mixed-mode loading, irrespective of the location of the notched crack.With their three-point bending tests under mixed-mode loading,while initial damage was observed at the tip of the notch,the failure occurred at the centre of the beam,and not at the notch.The central crack Brazilian disc(CCBD)subjected to diametral compression has been widely used to investigate the Mode I,Mode II and mixed-mode fracture of brittle rocks(Atkinson et al.1982;Shetty et al.1985;Al-Shayea 2005;Awaji and Sato1978).More commonly,if a CCNBD specimen is loaded with the crack orientated at an appro-priate angle with respect to the loading direction,a mixed-mode I–II stressfield can be achieved at the crack tips(see Fig.2).The applied stress translates into a stress intensity factor at the crack tip.The equations given by LEFM to calculate stresses and the stress intensity factor for a crack under tensile loading are also applicable for a crack under com-pressive loading;however,they use opposite signs;that is, K I and K II become negative.A negative K I indicates compressive stress acting at the crack tip,and a negative K II indicates an opposite direction for the shear stress acting parallel to the crack plane.As shown in Fig.3,the inclination angle(h)of a compressively loaded crack is such that the crack extension occurs parallel to themajor Fig.2CCBD specimen under diametral compressionFracturing of Rocks Under Static and Cyclic Loading1037principal compressive stress (see Fig.3a),while it is par-allel to the minor principal tensile stress in the case of a crack under a tensile stress (see Fig.3b).The fracture stresses for Mode I,Mode II and mixed-mode I–II compressive loading can be found similarly to those for tension loading by using the three fracture criteria used in fracture mechanics (Erdogan and Sih 1976;Hussain and Pu 1974;Sih 1974).In contrast,some researchers have provided a closed-form solution for the stress distribution in cracked and uncracked disc specimens under diametral compression (Atkinson et al.1982;Shetty et al.1985;Awaji and Sato 1978).Shetty et al.(1985)first used a CSNBD specimen to calculate both Mode I and Mode II fracture toughnesses of ceramics.Atkinson et al.(1982)and Awaji and Sato (1978)developed dimensionless Mode I stress intensity factor (NI)and dimensionless Mode II stress intensity factor (NII)solutions depending on the dimensionless notch length a (a /R )and the notch inclina-tion angle (b )with respect to the loading direction.3Sample Preparation and Testing Procedure Three rock types were tested in this study:Brisbane tuff,granite and sandstone,which represented medium-,high-and low-strength rocks,respectively.Brisbane tuff,with typically 97MPa uniaxial compressive strength (UCS),was a host rock of Brisbane’s first motorway tunnel,CLEM7,from which core samples were obtained.The granite blocks,with typically 210MPa UCS,were from the Keperra Quarry,Brisbane.The sandstone samples,with typically 37MPa UCS,were from Helidon,Brisbane.All samples were reasonably isotropic,and the CCNBD spec-imens were used in both the static and cyclic tests.The CCNBD method has advantages over other ISRM-proposed fracture toughness tests in terms of the simplicity of sample preparation and the reduced material required for testing.In order to obtain accurate fracture toughness values,a sharp crack tip must be NBD specimens achieve this by having a sharp chevron notch tip instead of straight through notch.Another advantage of the CCNBD method over other ISRM methods is increased precision,resulting from a higher load capacity and more consistent results.The geometry of a CCNBD specimen is illustrated in Fig.4.The thickness of the notches,t ,was 1.5mm and the thickness of the specimens,B ,was 25mm.The inner chevron notched crack length,2a 0,was 16–18mm and the outer chevron notched crack length,2a 1,was 36–37mm.All geometrical dimensions should be converted to dimensionless parameters with respect to the specimen radius and diameter.Specimen dimensions are given in the suggested ISRM methods (ISRM 1995).Other specimen geometrical dimensions are possible;however,in order to have a valid test,the two most important dimensions,that is,the dimensionless final notched crack length (a 1)and the dimensionless quantity (a B ),must fall within the range outlined in the suggested ISRM methods (ISRM 1995).The dimensionless initial crack length (a 0=a 0/R ),the dimensionless final notched crack length (a 1=a 1/R )and the dimensionless quantity (a B =B /R )are the three basic dimensions for the CCNBD specimens.All specimen geometries used in this study were in the valid ranges suggested by the ISRM (ISRM 1995).A circular 40mm diamond saw was used to cut the required notch (see Fig.5).A specially designed jig rec-ommended by the ISRM was used to ensure that the chevron notches were exactly in the centre of the disc.Some prepared CCNBD specimens are shown in Fig.5b.The crack displacement was measured as crack mouth opening displacement (CMOD)across the crack mouth.AFig.3Crack propagationpaths under:a compression and b tension1038N.Erarslan,D.J.Williamsclip gauge for measuring the notch opening was attached to the specimen across the chevron notch,and an Instron 2670series crack opening displacement gauge was used to measure the CMOD (see Fig.5c).The gauge length was 10mm and the maximum travel was 2mm.The gauge met the requirements set out in British standard BS 5447and American standard ASTM 39970T.4Experimental Results 4.1Static TestsDisc specimens were loaded at various inclination angles (b )to the static diametral compressive loading direction,rangingfrom 0°to 70°.Load-controlled testing was adopted and loading was continued until failure.Load,diametral dis-placement and crack mouth displacement were continually recorded during each test using a computerised data logger.As the loading type was diametral compression in order to create compression-shear loading on the pre-existing crack plane,the crack initiation angle was positive (counterclockwise)and the crack propagation direction tended to be parallel to the direction of compressive loading.In general,the ultimate failure load for all rock types increased up to b =33°(see Table 1).The reason for this maximum ultimate failure load may be the fact that the highest shear stress occurs with this crack inclination angle under compressive loading.If a CCNBD specimen is loaded with the crack oriented at an appropriate angle (b )with respect to theloadingFig.4CCNBD specimen geometry with recommended testfixtureFig.5CCNBD specimen preparation equipment:a diamond saw,b prepared CCNBD specimens and c loading plates and CMOD transducerFracturing of Rocks Under Static and Cyclic Loading 1039direction,a mixed-mode I–II stress field can be achieved at the crack tips,and the crack propagates at an angle (h )with respect to its crack plane.The crack initiation angle (h )was found in the experimental results reported herein to be strongly dependent on b .It was found that cracks initiated at an angle of 70°–100°relative to the original crack plane when the inclined crack was subjected to diametral com-pressive load.The tested Brisbane tuff,granite and sand-stone specimens are shown in Fig.6.The experimental results showed that cracks initiated at the tip of the notch for specimens of all three rock types for values of b up to 30°.However,one of the most important observations made was that the location of the crack initiation moved to the centre of the notched crack for b C 30°.It was also observed that,with 70°inclined cracks in sandstone and granite specimens,single coplanar shear cracks appeared individually at one end of the tip of the cracks.The dependence of h on b is shown in Table 2for the Brisbane tuff,granite and sandstone specimens.In general,h increases with increasing b for all three rock types.Theresults show that diametral compressive loading along the crack plane in CCNBD specimens always creates mixed-mode fracturing,without any clear Mode II fracturing,although the crack is subjected to compressive-shear loading.Crack displacement (CMOD)was monitored continu-ously until failure.Figures 7,8and 9show the displace-ment responses of the chevron notched crack mouths,for various b ,for Brisbane tuff,granite and sandstone CCNBD specimens,respectively.In general,it is clear that all notched cracks opened for b of up to 28°,for all three rock types.It was concluded that the effective normal stress perpendicular to the crack plane is mostly tensile,which causes the crack to open.However,notched cracks in specimens of the three rock types showed different responses to diametral compression for b =30°and 33°.For instance,for b =30°and 33°,notched cracks in Brisbane tuff CCNBD specimens initially closed,then opened with increasing plastic behaviour up to failure (see Fig.7).In contrast,for b =30°the notched crack in a granite CCNBD specimen opened,while for b =33°it closed (see Fig.8).For b =30°the notched crack in a sandstone CCNBD specimen opened,while for b =33°it closed slightly (see Fig.9).The smallest crack displacement was obtained for the granite specimens,since it is the strongest and most brittle of the three rock types tested.Another important observation from the load–CMOD plots is the clear plastic deformation prior to failure in opening fracturing mode in specimens of all three rock types,which suggests a fracture process zone (FPZ)in front of the crack tip.When crack closing starts,hardly any plastic deformation takes place prior to failure.In particular,no plastic deformation took place prior to failure for b =45°and 70°for specimens of all rock types.4.2Cyclic TestsIn the cyclic tests,ramp waveform-type diametral com-pressive loading with constant amplitude and increasing mean level was used.This approach to the K IC of rock isTable 1Failure loads obtained for Brisbane tuff,granite and sandstone CCNBD samplesInclination angle (b )Failure load (kN)Brisbane tuff Granite Sandstone Repeat 10°4.49.6 1.9Repeat 2 4.19.0 1.7Repeat 128° 4.910.2 2.4Repeat 2 4.79.5 1.8Repeat 130° 4.410.1 2.1Repeat 2 4.89.6 2.3Repeat 133°5.311.0 2.2Repeat 2 5.711.3 2.5Repeat 145° 4.910.2 2.1Repeat 2 4.49.7 2.3Repeat 170° 4.79.8 2.5Repeat 24.39.42.2Fig.6Tested CCNBD specimens:a Brisbane tuff,b granite and c sandstone1040N.Erarslan,D.J.Williamstermed ‘increasing cyclic loading’,and has not previously been reported in the literature.The loading frequency was 1Hz for all tests,and the amplitude is expressed as an absolute (±value)equal to the total range.An illustration of the cyclic loading is given in Fig.10.Four different amplitudes were chosen to investigate the effect of fatigue on the K IC of Brisbane tuff:0.45kN at 10%static ultimate load (SUL),0.9kN at 20%SUL,1.35kN at 30%SUL and 1.8kN at 40%SUL.A series of diametral increasing cyclic compressive loading tests was performed on 12CCNBD Brisbane tuff specimens.The analyses of these tests focused on the reduction of Mode I K IC under cyclic loading with different amplitudes.The K IC value of Brisbane tuff under static loading was calculated as 1.12–1.5MPa H m using the methods suggested by the ISRM (Ouchterlony 1988).The main purpose of this comparison was to show the clear reduction of the ultimate failure load,which resulted in a reduction of Mode I stress intensity due to rock fatigue.An attempt was made to show that crack propagation causing failure was possible with lower stress intensity values (K I )at the crack tip than the previously determined (static)critical stress intensity value (K IC ).This result goes against the classical theory,which predicts that there will be no crack growth as long as K I is less than K IC .According toTable 2b and h values for Brisbane tuff,granite and sandstonesamplesInclination angle (b )Initiation angle (h )Brisbane tuffGranite Sandstone 0°0°0°0°28°65°60°65°30°75°70°75°33°80°70°80°45°85°80°80°70°90°90°90°Fig.7Crack displacement under mixed-mode loading of Brisbane tuff CCNBDspecimensFig.8Crack displacement under mixed-mode loading of granite CCNBDspecimensFig.9Crack displacement under mixed-mode loading of sandstone CCNBDspecimensFig.10Number of load cycles illustrating cyclic loadingFracturing of Rocks Under Static and Cyclic Loading 1041the test results,the maximum reduction in the static K IC of 46%(from1.12to0.61MPa H m)was obtained with the highest amplitude increasing cyclic loading:that is,1.8kN (40%SUL).This reduction has implications for the investigation of the effect of cyclic loading on the fracture resistance of rock cracks.A second series of diametral increasing cyclic com-pressive loading tests was performed on27CCNBD Brisbane tuff specimens with crack inclination angles b of 30°,45°and60°,tested under amplitudes of0.45,0.9and 1.35kN.Load and CMOD values were recorded continu-ously up to the failure of the specimens.The failure load and the number of cycles for each inclined crack,tested under various amplitudes of cyclic loading,are shown in Table3.The results show that the failure load obtained on increasing cyclic loading decreased between30and45% compared with the values obtained under static loading.According to their initiation position,wing cracks can be classified as upper external wing cracks,lower external wing cracks or fatigue cracks(see Fig.11).Upper and lower external wing cracks were observed in all specimens tested,and most of them propagated to the top and bottom edges of the disc specimens at an angle to the crack plane. However,fatigue cracks did not propagate along a typical path;some of them propagated parallel to the notched crack plane and some propagated at an angle.Further, because brittle fracture occurred rapidly under the load-controlled testing,it was not possible to separate the crack initiation and propagation stages.Thus,it was difficult to determine whether external wing cracks were initiated and propagated before fatigue cracks formed.It was believed that,for static loading,increasing the Mode II loading of a specimen initiated wing cracksfirst.Even though tensile wing fractures were initiated,a secondary fracture is instigated with an increasing shear load(Hussain and Pu 1974).However,mixed-mode fracturing is evident,and different mechanisms contribute to crack propagation under cyclic loading.An interestingfinding from the inclined notched crack increasing cyclic loading tests was the absence of post-peak strain softening,while this was observed in the Mode I cyclic loading tests.Figure12shows the load–CMOD and CMOD versus number of cycles plots for b=30°CCNBD specimens under diametral increasing cyclic compressive loading with an amplitude of0.45kN at10% of SUL.The load–CMOD plots showed irreversible strain accumulation with a decreasing crack mouth opening rate, prior to the crack opening at a faster rate up to failure(see Fig.14b).Figure13shows the load–CMOD and CMOD–number of cycles plots for b=45°CCNBD specimens under diametral increasing cyclic compressive loading with an amplitude of0.45kN at10%of SUL.These tests showed the development of wing cracks and fatigue cracks similar to those seen for b=30°.However,more fatigue cracks were initiated and were closer to the centre of the notched crack at this angle,rather than close to the tip of the not-ched crack and almost parallel to the notched crack plane. The fatigue cracks can interact and coalesce with one another to produce continuous plastic strain accumulation and form crushed or small particles,different from the more brittle failure mechanism seen on static loading.Interestingly,the b=45°inclined notched cracks were found to open right up to failure in all three increasing cyclic compressive loading test repeats,while under static loading the b=45°inclined notched cracks closed right up to failure.This behaviour was also observed for some b=30°and60°inclined pared to the static damage mechanism for the b=45°inclined notched crack,a different fatigue damage mechanism would be expected under cyclic loading in front of the tip of the b=45°inclined notched crack.The possible fatigue damage mechanism is described in Sect.5.Examples of the load–CMOD,CMOD–number of cycles and the axial dis-placement–number of cycles plots for the b=45°inclined notched crack under various amplitudes of increasing cyclic compressive loading tests are shown in Fig.14.The results for b=60°inclined notched crack speci-mens are shown in Fig.15,which are similar to the wing and fatigue crack trajectories obtained for the b=30°,45°and60°inclined notched cracks.However,fatigue crack propagation trajectories at the tips of the b=60°inclined notched crack was more parallel to the notched crack plane compared with those for b=30°and45°.Some of the b=60°inclined notched cracks were found to open right up to failure under increasing cyclic compressive loading as shown in Fig.16.Test results for inclined notched cracks under increasing cyclic compressive loading show that the typical CMOD response is different from the response to static loading.It is hard to understand and explain how the b=60°inclined notched crack can open right up to failure under cyclic loading,while this angle has been determined to be a crack closing angle under static loading.These results clearly show that different damage mechanisms take place in front of the inclined notched crack due to rock fatigue on cyclic loading.5Numerical Simulations and Scanning Electron Microscope(SEM)Analysis5.1Numerical ModellingA series offinite element simulations were conducted to model notched crack initiation and propagation under static1042N.Erarslan,D.J.Williams。
破碎岩质边坡锚墩式主动防护网设计方法
DOI ：10.16031/ki.issn.1003-8035.2021.03-13破碎岩质边坡锚墩式主动防护网设计方法吴 兵1,2，梁 瑶1，赵晓彦2，唐晓波1，吴晓春1，罗天成2（1. 四川省交通勘察设计研究院有限公司，四川 成都 610017；2. 西南交通大学地球科学与环境工程学院，四川 成都 611756）摘要：现有公路（铁路）工程中的高陡岩质边坡，特别是风化作用强烈地区的岩质边坡，浅表层岩体多呈碎裂状。
采用传统SNS 主动防护网加固后，仍经常产生局部失稳、掉块等现象，部分甚至引起整体失稳。
因此，针对破碎岩质边坡的加固防护迫切需要进行结构及其设计方法改进。
本文提出一种锚墩式主动防护网新型组合结构及其受力计算和设计方法，可有效防止碎裂岩质边坡坡面破坏，同时保证边坡整体稳定。
工程应用表明，该组合防护结构具有良好的破碎岩质边坡加固效果，值得在工程建设中推广应用。
关键词：破碎岩质边坡；锚墩；主动防护网；设计方法中图分类号： P694;U213.1+58 文献标志码： A 文章编号： 1003-8035（2021）03-0101-08Design method of anchor pier type active protective net onfractured rock slopesWU Bing 1,2，LIANG Yao 1，ZHAO Xiaoyan 2，TANG Xiaobo 1，WU Xiaochun 1，LUO Tiancheng 2（1. Sichuan Communication Surveying & Design Institute , Co. Ltd., Chengdu , Sichuan 610017, China ；2. Faculty of Geosciences and Environment Engineering , Southwest Jiaotong University , Chengdu , Sichuan 611756, China ）Abstract ：The shallow surface rock mass of the high and steep rock slopes in the existing highway (railway) projects, especially with severe weathering slope rock mass, is mostly cataclastic. After the traditional SNS active protective net is adopted to reinforce the slope, the rock slope has been locally unstable or subject to overall instability. Therefore, it is necessary to improve the structure and the corresponding design method for the reinforcement and protection of cataclastic rock slope. A new type of combination structure of anchor-pier active protection net as well as the stress calculation and design method is put forward,which can effectively prevent the destruction of cataclastic rock slope surface and ensure the overall stability of the slope. It can be seen from the engineering application that the combined protective structure has good reinforcing effect on the cataclastic rock slope, and it could be applied in the engineering construction.Keywords ：fractured rock slope ；anchorage pier ；active protection net ；design method0 引言随着我国公路、铁路等基础设施建设的推进，工程中遇到了大量的岩质边坡崩塌破坏、风化剥落等问题，尤其在西部山区国（省）干道的升级改造过程中，这种现象最为严重[1 − 5]。
平坝山大型石灰岩露天矿边坡稳定性分析
第4"卷第1期2021年3月有色金属设计Nonferrous Metals DesignVol.48No.1March.2021平坝山大型石灰岩露天矿边坡稳定性分析童志鹏，李栓柱，吕林洪（昆明有色冶金设计研究院股份公司，云南昆明650051）摘要：平坝山石灰岩露天矿开采深度很大，存在软弱夹层，采场边坡的稳定性直接关系到矿山的正常运营，也影响到其深部延伸开采设计的合理性，因此其边坡稳定性分析评价至关重―。
根据工程地质条件和岩体质量评价，采用有限差分法FLAC26岩土边坡分析软件建立边坡模型对其各个帮的边坡进行稳定性计算分析。
分别计算了在自重、自重+爆破、自重+地震状态3种工况条件下的边坡安全系数，结果表明：该露天矿终了境界边坡处于稳定状态，满足安全等级的—求，说明该终了采场设计的边坡结构参数具有一定的可行性和合理性，同时也建议边坡靠帮时采用光面爆破、预裂爆破等减震技术措施，为该露天矿的持续安全开采提供了指导依据。
关键词：采场边坡；露天采矿；稳定性；安全系数；石灰岩中图分类号：TD216文献标识码：B文章编号：1004-2660（2021）01-0012-07Slope Stability Analysis of the Large Open-pit of Pingbashan Limestone MineTong Zhipeng,Li Shuanzhu,Lv Linhong(Kunming Engineering&Research Institute oO Nonferrous Metallurgy Co.,Ltd.,Kunming650051,China) Abstrach:Pingbashan limestone mine with weak intercalation has been opencast mined verg deeply.As the stability of stope slope directly beao on the normal operation and rational deep mining design of the mine,analysis and evvluation on it is vital.According to the engineering geological conditions and rock mass quality evvluation, FLAC2D software is employed i establish a slope model and calculate and analyze the stability of all slopes. Slope safety factors arc calculated respectively u ndec three working conditions of dead weighi,dead weighi+ blasting and dead weighi+earthquake.The resulis show thai the slope of the ultimate Umil is stable,meeting the requirements of security,and the slope stnucture9801X1000for the design is of feasibility and rationality.In addition,smooth blasting and presplitting blasting are recommended for shock absorbing when s lope approaches the boundary.The research provides guiganca for the cantinued and safe mining.Keywords:Slope of open一pit；Open pit；Stability；Safety factoa；□1X101-0o引言平坝山石灰岩矿山为1座在建露天矿山，该石灰岩露天矿每年生产规模100万t/a,设计采用露天开采方式，缓帮开采工艺，公路汽车开拓运输方式。
BQ分级法在边坡岩体基本质量分级中的应用分析
BQ分级法在边坡岩体基本质量分级中的应用分析虞金林(中国建筑材料工业地质勘查中心江苏总队，江苏南京211135)摘要:利用BQ分级法对边坡岩体质量特征进行研究，通过岩块强度及岩体完整性对工程岩体自身性质进行分级。
结合主要结构面类型与延伸性修正因素姿主要结构面产状影响修正因素K5以及地下水影响修正因素K4三个修正因素对边坡工程岩体质量进行分级,分级方法具有较强的科学性和实用性。
关键词:BQ法;边坡;岩体;修正因素;强度Abstract:The quality characteristics of slope rock mass are studied by using BQ classification method.The strength and the integrity of rock mass are considered to classificify the rock mass's property.Then,the rock mass quality of slope engineering is classified by combining the main structural plane type and elongation correction factor姿，the main structural plane occurrence correction factor K5and the groundwater influence correction factor IK,the classification method is scientific and practical.Key words：BQ method；slope；rock mass；correction factor；strength［中图分类号］U445.7+2［文献标识码］A［文章编号］1004-5538(2021)02-0050-040引言岩体基本质量分级，是各类型工程岩体定级的基础。
九日山摩崖石刻危岩体成因分析及加固工作方法论述
1引言石窟寺和石刻是石质文物类型中非常重要的两大分支,一类是天然岩体上直接雕凿的图像、文字等形成的文化遗存,另一类是在不同岩性上开挖建造的石窟寺,石窟寺和石刻岩石材料几乎涵盖了岩石的各大类型。
岩石依据其地质成因可将其划分为岩浆岩、沉积岩和变质岩三大类。
岩浆岩可分为喷出岩及侵入岩,喷出岩类岩石表面多孔洞,不利于雕刻成型,所以,以该类岩石为材料的石刻、造像及石质文物数量不多,侵入岩类的石质文物岩石类型最具代表性的无疑是花岗岩,而本文阐述的九日山摩崖石刻就是南方典型的以花岗岩为雕刻材料的石刻类型。
据志书记载,九日山历代均有石刻。
唐代以来不少文人墨客的墨迹留在岩壁间,因年代久远,或因风化磨灭,或因流土积埋,或因人为之因,部分已难寻踪迹,但其核心之石刻保存完好。
九日山现存古代摩崖石刻共77方,年代从北宋早期至清朝乾隆时期,反映海外交通的祈风石刻10方,记载从北宋崇宁三年(1104年)至南宋咸淳二年(1266年)泉州郡守偕市舶官员为番船祈风,预祝一帆风顺、满载而归的史实。
在九日山现存的摩崖石刻中,内容包括景迹题名、登临题诗、游览题名、修建纪事、海交祈风,题刻中行、隶、篆、楷并举,留名者达250多名,以蔡襄、苏舜元、苏绅、虞仲房、马负书等人的题刻为佳,是研究我国古代书法艺术的珍贵资料。
2危岩体机理成因分析通过对九日山摩崖石刻的勘察共发现包括23处危岩体,且以滑动式、倾倒式和坠落式为主,针对危岩体与摩崖石刻的特征,加固方案以锚杆锚固为主要加固措施,以危岩体的清除、裂隙灌浆、黏结等为辅助保护措施,以达到消除和减少地质灾害发生的目的。
崩塌是九日山摩崖石刻景区内主要的不良地质现象。
岩体内发育多条近水平层面裂隙和纵向构造裂隙,这些裂隙交【作者简介】何春燕（1987~），女，福建南安人，馆员，从事摩崖石刻、泉州古代海外贸易研究。
九日山摩崖石刻危岩体成因分析及加固工作方法论述Cause Analysis and Reinforcement Method of Dangerous Rock Bodyof Inscriptions on Precipices in Jiuri Mountain何春燕（南安市九日山文化保护管理中心，福建南安362300）HE Chun-yan(Nan ’an Jiuri Mountain Cultural Protection and Management Center,Nan ’an 362300,China)【摘要】针对九日山危岩体存在崩塌、滑移、倾倒的问题，论文以九日山危岩体为例，叙述了常见的加固措施，分析了危岩体机理现状，同时针对其成因进行了探究，采用微型锚杆结合裂隙灌浆和砌筑的方法解决了石刻周边危岩体存在的安全隐患，对石刻本体的保护起到了极其重要的作用。
Rock Climbing Dash
Title: Rock Climbing DashIn the realm of adventurous sports, rock climbing stands out as a thrilling and challenging pursuit. Let's explore the wonders of rock climbing and discover its many charms.The theme of this article is the excitement and significance of rock climbing. We will examine different aspects of this dynamic sport to understand its impact on our lives.The structure of the article will be as follows. First, we'll describe the details of rock climbing, including actions, venues, equipment, and the unique sensations it evokes. Then, we'll discuss the numerous benefits of rock climbing, ranging from physical health to mental well-being and social connections.Now, let's delve into the specifics. On the rock face, climbers move with precision and strength. The actions are a combination of reaching, pulling, and stepping. Each movement is carefully calculated as climbers ascend the vertical terrain. Their fingers grip holds with determination, while their feet find purchase on small ledges. Venues can range from indoor climbing gyms with colorful routes to majestic outdoor cliffs surrounded by nature. Essential equipment includes climbing shoes with sticky soles, a harness for safety, a chalk bag to keep hands dry, and a rope for belaying. The feeling of being suspended on the rock, relying on one's own strength and skill, is indescribable. It's as if you're conquering a mountain, one hold at a time.The benefits of rock climbing are manifold. Physically, it provides an excellent workout that builds strength, endurance, and flexibility. It's like a sculptor shaping the body into a fit and capable form. As the saying goes, "A strong body is the foundation of a great life." Rock climbing helps build this foundation. Mentally, it hones focus, problem-solving skills, and courage. The challenges of finding the right route and overcoming obstacles require mental toughness and perseverance. After a successful climb, there's a sense of accomplishment and confidence that can carry over into other aspects of life. Socially, rock climbing brings people together. Whether it's climbing with a partner or joining a climbing community, it creates a sense of camaraderie and shared adventure.In conclusion, rock climbing is a source of boundless energy and passion that enriches our lives in countless ways. It offers excitement, challenge, and a path to a healthier and happier existence. So, put onyour climbing gear, reach for the heights, and embark on a rock climbing dash.。
气力输送技术在金牛天铁焦化除尘灰输送中的应用
科学技术创新2021.04应力判据对待开挖隧道进行岩爆预测时,优先考虑使用王兰生和陶振宇判据。
参考文献[1]谢和平.深部岩体力学与开采理论研究进展[J].煤炭学报,2019,44(5):1283-1305.[2]唐宝庆,曹平.岩爆预测方法的分析[J].江西有色金属,1997,11(3):24.[3]COOK.N.G.W.The basic mechanics of rockbursts[J].Journal of the South African Institute of Mining &Metallurgy ,1963.[4]HOEK.E.,DIEDERICHS.M.S.Empirical estimation of rock mass modulus [J].International Journal of Rock Mechanics and Mining Sciences.2006,43(2):203-215.[5]RUSSENES.B.F.Analysis of rock spalling for tunnels in steep valley sides (in Norwegian )[D].1974.[6]陶振宇.高地应力区的岩爆及其判别[J].人民长江,1987(5):27-34.[7]徐林生,王兰生,李永林.岩爆形成机制与判据研究[J].岩土力学,2002(3):300-303.[8]冯涛,谢学斌,王文星,等.岩石脆性及描述岩爆倾向的脆性系数[J].矿冶工程,2000,0253-6099.[9]谢和平,W.G.Pariseau.岩爆的分形特征和机理[J].岩石力学与工程学报,1993(1):28-37.[10]WANG.J.A.,prehensive prediction of rockburst based on analysis of strain energy in rocks [J].Tunnelling and Underground Space Technology ,2001,16(1):49-57.[11]BARTON.N.R.,LIEN.R.,LUNDE.J.Engineeringclassification of rock masses for the design of rock support[J].Rock mechanics &rock engineering ,1974,6(4):189-236.[12]王兰生,李天斌,徐进,等.二郎山公路隧道岩爆及岩爆烈度分级[J].公路,1999(2).[13]夏舞阳.高地应力场单线铁路隧道岩爆预测研究[D].成都:西南交通大学,2018.基金项目:国家自然科学基金(51809221);深部岩土力学与地下工程国家重点实验室开放基金(SKLGDUEK1910);蔓耗至金平高速公路项目草果山隧道岩爆预测与防控关键技术研究(JTSZ-MJGS-2019-042)。
Rock Climbing
Rock ClimbingRock climbing is a thrilling and challenging sport that has gained popularity worldwide. It involves ascending steep rock formations using various techniques and equipment. Whether you are a beginner or an experienced climber, rock climbing offers a unique opportunity to test your physical and mental strength while enjoying the beauty of nature. One of the key aspects of rock climbing is the equipment used. Climbers rely on a harness, rope, carabiners, and other safety gear to ensure their protection during the ascent. Additionally, specialized climbing shoes with sticky rubber soles provide the necessary grip on the rock surface, allowing climbers to maintain balance and make precise movements.As rock climbing is a physically demanding activity, it requires strength, endurance, and flexibility. Climbers must use their entire body to maneuver through challenging routes and overcome obstacles. This sport not only strengthens the muscles but also improves coordination and body awareness.Apart from the physical benefits, rock climbing also has a positive impact on mentalwell-being. The focus and concentration required to navigate difficult routes help climbers clear their minds and find a sense of calmness. Overcoming fears and pushing personal limits fosters self-confidence and boosts self-esteem. Moreover, being surrounded by nature's beauty provides a serene and peaceful environment that can reduce stress and improve overall mental health.Rock climbing is a diverse sport with various forms and styles. Traditional climbing involves placing protective gear as the climber ascends. Sport climbing, on the other hand, relies on pre-placed bolts for protection. Bouldering is a type of climbing without the use of ropes or harnesses, typically done on shorter routes. Each style presents its own challenges and requires different skills, allowing climbers to continually learn and progress.Safety is of utmost importance in rock climbing. Before embarking on any climb, it is essential to check the quality of the rock, weather conditions, and potential hazards. Proper training and knowledge of climbing techniques are crucial to prevent accidents and ensure a safe experience. Climbing with a partner or in a group adds an extra layer of security, as they can provide assistance and support if needed.Rock climbing is not limited to outdoor settings. Indoor climbing gyms have become increasingly popular, providing climbers with the opportunity to train and practice in a controlled environment. These facilities offer a variety of routes and difficulties to cater to climbers of all levels. Indoor climbing also allows for year-round participation, regardless of weather conditions.In conclusion, rock climbing is a captivating sport that combines physical strength, mental focus, and a love for nature. It offers a unique challenge and an opportunity for personal growth. Whether you choose to climb outdoors or indoors, rock climbing provides an exhilarating experience that pushes boundaries and fosters a sense ofaccomplishment. So grab your gear, find your route, and embark on an adventure like no other. Happy climbing!。
Rock Climbing Challenges
Rock Climbing ChallengesRock climbing is an exhilarating and demanding sport that tests both physical and mental strength. It requires climbers to overcome various challenges on their journey to reach the top. In this article, we will explore some of the most common challenges faced by rock climbers.One of the primary challenges in rock climbing is the unpredictable nature of the terrain. Each climbing route presents its unique set of obstacles, such as steep cliffs, narrow ledges, or overhanging rocks. Climbers must carefully analyze the route, plan their moves, and adjust their techniques accordingly. This requires a high level of concentration and problem-solving skills.Another challenge in rock climbing is the physical demands it places on the climber's body. Climbing requires strength, flexibility, and endurance. Holding onto small handholds and footholds for extended periods can be physically exhausting. Climbers must build up their upper body and core strength to tackle difficult routes successfully. Regular training and conditioning are essential to overcome these physical challenges. Fear and mental resilience are also significant challenges in rock climbing. Climbing heights can trigger fear and anxiety in even the most experienced climbers. Overcoming this fear requires mental resilience, focus, and confidence. Climbers must learn to manage their emotions and stay calm in stressful situations. Developing a positive mindset and trusting one's abilities are crucial in conquering these mental challenges. Weather conditions are another factor that adds complexity to rock climbing. Outdoor climbers must consider factors such as temperature, wind speed, and precipitation before attempting a climb. Unfavorable weather conditions can make the rock slippery or increase the risk of falling. Climbers must be prepared to adapt their plans or postpone their climbs if the weather becomes unfavorable.Equipment failure is yet another challenge that rock climbers may face. The safety of climbers heavily relies on their gear, including ropes, harnesses, and carabiners. Regular equipment inspections and maintenance are necessary to prevent accidents due to equipment failure. Climbers must also be knowledgeable about the proper use of their gear and ensure that it is in good working condition before every climb.In conclusion, rock climbing presents a wide range of challenges that climbers must overcome to succeed. From navigating difficult terrains to building physical strength and mental resilience, climbers need to be prepared for the obstacles they may encounter. By embracing these challenges and continuously improving their skills, climbers can experience the thrill and satisfaction of reaching new heights in the world of rock climbing.。
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tests are available to obtain discontinuity properties. Testing in large quantities is, however, time consuming and troublesome. Continuum calculations for engineering structures in or on a rock mass, whether analytical or numerical, cannot be appropriate, as the simplifications needed to present the rock mass as a continuum are so substantial that it is nearly always highly questionable to what extent the final calculation model still represents reality. Discontinuous ’distinct block’ numerical calculations can model the discontinuities and calculate the behaviour of a rock mass in all detail, provided that property data are available. Apart from the need to have powerful computers to do the large number of calculations required by the vast quantity of discontinuities, the test data needed for a detailed numerical discontinuous calculation are never available. An often applied practice to avoid these problems is to simplify the discontinuity model, and estimate or
The classification system is based on a three step classification system and allows for correction for weathering (Hack et al., 1996, 1997a) and excavation disturbance (Hack, 1996). The system classifies rock mass parameters in one or more exposures (step 1). These parameters are corrected for the influence of weathering and excavation disturbance in the exposures and parameters important for the mechanical behaviour of a the rock mass in an imaginary unweathered and undisturbed ’reference’ rock mass are calculated. The slope stability assessment thence allows assessment of the stability of the existing or any new slope in the ’reference rock mass’, with allowance for any influence of excavation method to be used for the new slope, and future weathering. This procedure allows a rock mass assessment based on rock mass parameters that are independent from local weathering and excavation disturbance as found in the exposures, but allows for the influence of future weathering on the rock mass at the location of the slope and the disturbance caused by the method of excavation used for the slope (Hack, 1996).
Rock mass strength by rock mass classification. Robert Hack (1997). South African Rock Engineering Congresspp. 346-356
Rock mass strength by rock mass classification
346
Rock mass strength by rock mass classification. Robert Hack (1997). South African Rock Engineering Congress (SARES) Johannesburg, RSA. pp. 346-356
guess the properties or to use literature values. To what extent the result is still representative for the real situation is a question that often remains unanswered.
ABSTRACT: The strength of a rock mass for foundation purposes is for a large part determined by the discontinuities in the rock mass. Numerical calculations of discontinuous rock masses prove often to be cumbersome and unreliable. Rock mass classification may be an equal or more reliable methodology. The Slope Stability Probability Classification (SSPC) system designed for slope stability may be used for this purpose. The system has been developed during four years of research in Falset, province Tarragona, Spain. The rock slope classification scheme assesses orientation dependent and orientation independent stability. The orientation independent stability assessment leads to a rock mass strength criterion based on classification data, e.g. intact rock strength, discontinuity spacing and discontinuity condition. The criterion is developed in the context of a slope stability classification system, however, there is no reason that the criterion is not also valid for the determination of rock mass strength for other purposes, such as foundations on a discontinuous rock mass. The results of the strength criterion are compared to the results of the ’modified Hoek-Brown strength criterion’ and to the rock mass strength as determined by Bieniawski’s classification system.
2 ROCK MASS CLASSIFICATION SYSTEMS
An altogether different approach to assess the engineering behaviour of a rock mass is rock mass classification. In a classification system empirical relations between rock mass properties and the behaviour of the rock mass in relation to a particular engineering application, are combined to give a method of designing engineering structures in or on a rock mass. Rock mass classification has been applied successfully for some years in tunnelling and underground mining in, for example, Southern Africa, Scandinavia and Canada (Barton, 1976, 1988, Bieniawski, 1989, Laubscher, 1990). Some rock mass classification systems (Bieniawski, 1989, Hack et al., 1993, 1996, Hoek et al., 1992, Serafim et al., 1983) result in empirical strength criteria for a rock mass.