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1.
Determination of Yield Surfaces for Isotropic Non-Cohesive Particulate Materials by the Discrete Element Method 总被引：1，自引：1，他引：0
J. A. Fleischmann M. E. Plesha W. J. Drugan 《Geotechnical and Geological Engineering》2014,32(4):1081-1100
We perform numerical simulations using the discrete element method (DEM) to determine yield surfaces for large samples of randomly packed uniform spheres with constant normal and tangential contact stiffnesses (linear spring model) and uniform inter-particle friction coefficient μ, for a large range of values of the inter-particle friction coefficient μ. The beauty of DEM is that the micromechanical properties of the spheres, especially the inter-particle friction coefficient μ, are known exactly. Further, simulations can be performed with particle rotation either prohibited or unrestrained, which provides an effective means for evaluating analytical models that employ these assumptions. We compare the resulting yield surfaces to the Mohr–Coulomb, Matsuoka–Nakai, Lade–Duncan, and Drucker–Prager yield surfaces, and determine the relationship between the resulting material friction angle ? on the macroscale and the inter-particle friction coefficient μ (or the inter-particle friction angle ? μ ) on the microscale. We find the Lade–Duncan yield surface provides the best agreement, by far, with the simulations in all cases. We also monitor inter-particle friction work and particle rotation within each specimen during the DEM simulations, both globally and on a particle-by-particle basis, and we compare the results obtained from DEM simulations in which the spheres were allowed full three-dimensional translational and rotational freedom of motion and DEM simulations in which particle rotation was prohibited. 相似文献
2.
运用80 t大型三维多功能土工试验机（3DMAS）,进行了不同应力幅值比下粗粒土与结构接触面大型三维循环直剪试验,深入分析了应力控制往返椭圆剪切路径下接触面切向位移、非共轴角和剪切柔度等三维力学特性以及应力幅值比的影响规律。应力控制往返椭圆剪切路径下,接触面产生了明显的x向和y向位移、非共轴角和剪切柔度。x向和y向位移幅值、剪切柔度峰值均随循环剪切的进行逐渐减小而后趋于稳定,表现出演化特性。非共轴角受切向应力幅值及切向应力增量方向共同影响,其最值、稳定值随循环周次基本保持不变;正向剪切时非共轴角最大值（最小值）与反向剪切时最小值（最大值）基本出现在同一位置。接触面剪切柔度与非共轴角随旋转角度的变化趋势相反,剪切柔度的增加会抑制非共轴角的发展,反之亦然,两者对立统一。应力幅值比对接触面切向位移间椭圆关系及其时程变化形式、切向应力位移类椭圆关系等影响较小,主要影响切向位移幅值及其偏移程度、切向位移间椭圆关系的长短轴大小及方向、切向应力位移类椭圆关系的长短轴大小、非共轴角的数值及其随旋转角度的变化形式和最值出现位置、剪切柔度随旋转角度的变化形式和峰值及其产生位置等。应力幅值比越大,切向位移幅值越大、向负向偏移越大,剪切柔度峰值越大,随循环剪切的进行减小的速率越慢。应力幅值比ξτ=1和ξτ≠1时接触面非共轴角和剪切柔度随旋转角度的发展变化形式差别很大。 相似文献
3.
Thomas Lebourg Hernandez Mickael Jomard Herv�� El Bedoui Bedoui Samyr Bois Thomas Zerathe Swann Tric Emmanuel Vidal Maurin Jr 《Landslides》2011,8(2):241-252
After a few years of research, the observation and the analysis of the deep-seated landslides suggest that these are mainly controlled by tectonic structures, which play a dominant role in the deformation of massif slopes. The La Clapière deep-seated landslide (Argentera Mercantour massif) is embedded in a deep-seated gravitational slope deformation affecting the entire slope, and characterized by specific landforms (trenches, scarps??). Onsite, the tangential displacement direction of the trenches and the scarps are controlled by the tectonic structures. The reactivation of the inherited fault in gravitational faults create a gouge material exposed to an additional mechanical and chemical weathering as well as an increased of leaching. The displacement of these reactivated faults gets increasingly important around the area of the La Clapière landslide and this since 3.6?ka BP. In this study, mechanical analysis and grain size distributions were performed and these data were analysed according to their proximity the La Clapiere landslide and times of initiation of the landslide by 10Be dating. Triaxial test results show that the effective cohesion decreases and the effective angle of internal friction increases from the unweathered area to the weathered area. The whole distribution of the grain size indicates that the further the shear zone is open or developed, the further the residual material loses its finest particles. This paper suggests that the mechanical evolution along the reactivated fault is influenced by the leaching processes. For the first time, we can extract from these data temporal behaviour of the two main mechanical parameters (cohesion and angle of internal friction) from the beginning of the La Clapiere landslide initiation (3.6 ka BP) to now. 相似文献
4.
Shear behaviour of the joints formed by the interface of two different material types, such as rock and cemented paste backfill, rock and concrete or two different rock types, have practical importance in many rock engineering activities. This paper presents the results of an experimental investigation into the shear behaviour of these special joints under pseudo-static shear velocity. Direct shear tests on concrete–plaster interfaces were carried out under boundary conditions of constant normal load and constant normal stiffness. Shearing velocities of the performed tests were in the range of 0.3–30 mm/min. The results of the shear tests conducted on the planar and rough artificial prepared joints showed that the shearing velocity has a significant influence on the shear strength, friction angle and shear stiffness of the hard–soft material interface. So that, these parameters were decreased when shear velocity was increased. Also, comparison of the tests results that performed on the concrete–plaster joints with those from tests on the plaster–plaster and concrete–concrete interfaces showed that the shear behaviour of concrete–plaster interface is governed mainly by the shear parameters of the plaster block (namely softer material). 相似文献
5.
池永翔 《中国地质灾害与防治学报》2008,19(1):28-31
文章在分析福建周宁县马头山滑坡的地质环境条件的基础上,阐述了滑坡的形态、滑面滑床特征和变形特征以及气象水文、地形地貌和人类工程活动等内外营力对该滑坡的影响,并对滑坡的形成过程和机理进行了详细分析。研究结果表明,该滑坡形成过程及机理为：开挖-滑带土浸水软化、抗剪强度降低或丧失-坡面、坡顶开裂和坡脚剪切破坏-剪切破坏区向上发展与后缘张裂隙贯通-滑面贯通、滑坡产生。根据定量分析计算,在连续降雨或暴雨条件下,该滑坡整体超过临界稳定状态而处于不稳定状态,滑坡可能继续失稳破坏。根据滑坡特征,提出了采取削坡减载、排水及坡面防护的综合治理方案。 相似文献
6.
Summary Direct shear tests, in which the behaviour of the rock surfaces during shear could be continuously observed, were used to study the shear failure of a profiled and clean discontinuity artificially prepared from natural sandstone. Displacement transducers were used to measure the normal and shear displacements. A series of strain gauges glued on the sides of the upper block provided information on the change of the stress field occurring close to the discontinuities whilst shear displacement increased, and these changes were then compared with the behaviour of the profiled surface. The results of the laboratory tests, the sequence of photographs taken for most of them, and the results conducted with a sample of similar shape made from the same rock material and tested in a rotary shear machine, allowed several stages and mechanisms of failure to be defined: static friction and mobilization of initial shear stiffness; mobilization of sliding; mobilization of brittle fracture; post-peak failure of the teeth; descent of the teeth; gliding and ploughing; commencement of second cycle of shearing. In many respects these stages are similar to those occurring between sliding surfaces of metal and suggest that the analyses developed in tribology may be relevant to the development of constitutive models for predicting the hydromechanical coupled behaviour of a discontinuity with shear displacement. Such models will have to consider these different stages of shear, because the original discontinuity changes its geometry with displacement and is filled with gouge which changes its grain size with displacement. 相似文献
7.
陕西泾阳东风高速远程黄土滑坡运动过程的模拟 总被引：1，自引：0，他引：1
陕西泾阳南塬的东风滑坡是一个典型的高速远程黄土滑坡,由于斜坡顶部的黄土台塬长期灌溉所诱发。通过野外调查,采取滑坡后缘斜坡的黄土试样,对斜坡中部的Q2黄土做天然含水率的固结不排水剪试验,对斜坡底部地下水位面附近的Q1黄土做饱和固结不排水剪试验,结果表明非饱和的Q2黄土和饱和的Q1黄土在破坏后都具有显著的应力降,但前者是由结构强度引起,而后者则是由剪切形成的超孔隙水压力引起,由此表明该斜坡一旦破坏,就会有较高的启动速度。对滑坡坡脚以外一级阶地上的砂卵层做环剪慢剪试验,测得其有效残余摩擦角,根据滑坡各部分含水状态给定孔隙水压力参数,利用Sassa. K滑坡运动模型对该滑坡运动过程进行模拟,从模拟结果反映出滑坡运动过程中的覆盖范围和速度的变化,模拟的滑坡运动距离和覆盖范围与实测比较吻合,最高速可达到37m s-1,为高速滑坡。黄土滑坡以高的初速度下滑到坡脚下一级阶地上的饱和砂卵层上,砂卵层上液化是导致其远程运动的主要原因。 相似文献
8.
As the traditional displacement value of a landslide is very easy to be affected by rainfall, it is very difficult to establish a stable and uniform destabilized criterion of landslide in terms of the displacement value. So, it determines that establishment of an effective and stable dynamic displacement prediction parameter is very important in forecast of the debris landslides caused by rainfall. In order to determine this kind of prediction parameter, this paper first completes analysis on the relationship between the destabilized mechanism of the debris landslide and the rainfall dynamic rules. The relationship above shows that the periodical change value of rainfall can be taken as the dynamic unload–load parameter (ULP) of landslide, and the homologous change value of mensal landslide displacement can be taken as the stability displacement response parameter (DRP). Then, on the basis of the relationship between the ULP and the stability DRP of this kind of landslide, the unload–load displacement response ratio (ULDRR) appraisal parameter of this kind of landslides is established in this paper. Finally, the stability of typical debris landslides in China has been systematically studied by means of ULDRR appraisal parameter and model. We find that the ULDRR values conform to the evolutional rule of slope deformation and instability. So, it has been proved that the ULDRR parameter and the appraisal model are suitable and effective for prediction and evaluation of stability and evolution rule of rainfall-induced landslides. 相似文献
9.
运用80 t大型三维接触面试验机,对初始静剪应力存在时粗粒土与结构接触面循环力学特性及初始静剪应力大小的影响进行了研究。循环剪切时,接触面沿初始静剪应力方向产生了明显的切向位移,且该位移与正交切向的剪切路程基本呈直线关系,该直线与初始静剪应力的夹角和初始静剪应力水平关系可用二次多项式描述。初始静剪应力大小对接触面抗剪强度、正交切向应力-应变关系形式影响较小,主要影响正交切向应力峰值、接触面剪切体变数值及剪切体变与切向位移关系等。初始静剪应力越大,该方向产生的切向位移越大,其正交切向应力峰值越小,该应力峰值对应的切向位移亦越小,接触面剪切硬化程度越高;初始剪切时接触面剪胀量越大,而后期循环剪切时剪缩量和剪胀量则越小。 相似文献
10.
Sumio Matsuura Takashi Okamoto Shiho Asano Hikaru Osawa Tatsuya Shibasaki 《Environmental Earth Sciences》2017,76(10):362
The displacement of a relatively small reactivated landslide in a snowy area in Japan was monitored over a long period. The displacement rate of the landslide, which was approximately of 20 mm d?1 before the formation of snow cover, decelerated drastically during the continuous snow cover period every winter period. Possible causes included reduction in the amount of water that reached the ground surface (MR: meltwater and/or rainwater) and increase in snow load. Given that the actual displacement of the landslide was far below the predicted value based on the relationship between landslide displacement and MR immediately before the continuous snow cover period, the deceleration of landslide displacement was more likely attributable to the increase in snow load than to the reduction in MR. An investigation of the link between snow load and landslide displacement showed a negative logarithmic relationship. A dynamic analysis based on the limit equilibrium method showed that snow load increases the effective normal stress and the stability of a landslide in which the mean inclination angle of the slip surface is smaller than the internal friction angle. The stability of the actual slope was also analyzed by conducting soil tests on samples collected at the site and using the resultant parameters. The analysis also showed that the increase in snow load increases the safety factor and reduces the landslide displacement. The displacement of a relatively small landslide that has a shallow slip surface was found to be greatly influenced by snow cover. 相似文献
11.
斜坡临滑形变能释放与滑体起程速度关系的探讨 总被引：1，自引：1，他引：0
斜坡内聚集的巨大剪切形变能在临滑时释放,坡体能量释放率具有力的量纲,在坡体能量释放率幅值大于锁固段潜滑带抗剪强度幅值的情况下,坡体临滑释放的形变能将大于潜滑带岩体破裂需要的能量,所大于的部份将转变成滑体动能,滑动为剧动式滑坡;反之,则为缓动式滑坡。剧动式滑坡横截面上的弹冲速度与该点切应力的大小成正比。潜滑面附近坡体介质的切应力和切应变能密度最大,滑动时获得的弹冲速度也最大。导得蕴涵丰富信息量的斜坡弹性势能变化率曲线及其表达式,通过解析及Matlab图解形式对坡体的形变能聚集、临滑形变能释放量及其与滑体启动速度、启动方式进行了阐述。 相似文献
12.
运用80 t大型三维接触面试验机,对不同法向刚度下粗粒土与结构接触面三维静动力学特性进行了试验研究,重点分析了法向刚度对接触面力学特性的影响规律。法向常刚度条件下,接触面在单调剪切时均先剪缩再剪胀、法向应力先减小后增大;循环剪切时接触面不可逆性剪切体变呈单调增长、可逆性剪切体变峰值逐渐减小后趋于稳定,切向应力峰值不断减小,抗剪强度逐渐减小,主应力比峰值则基本保持不变。法向刚度主要影响剪切体变、可逆性剪切体变、切向应力、主剪应力等接触面力学性能参数的大小;法向刚度越大,单调剪切时法向应力变化越大、切向应力峰值越大、剪缩和剪胀量越小;循环剪切时不可逆性剪切体变增长越慢、最终值越小,抗剪强度减小越快、达到0时对应的循环周次越少。法向刚度对剪切体变、可逆性剪切体变、主剪应力、主应力比等性能参数与切向位移的关系形式及接触面摩擦角基本没有影响。 相似文献
13.
Marwa Feligha Farid Hammoud Mouloud Belachia Mohamed Salah Nouaouria 《Geotechnical and Geological Engineering》2016,34(2):567-578
Soil shearing resistance is very important while designing various structures which have direct contact with soil, for example, sheet piles, piles, retaining walls, reinforced earth structures and shallow foundations. Even though designers use empirical values for their design, it is very important to obtain more accurate values for soil–solid materials shearing resistance. In this work, laboratory tests have been carried out to investigate the effect of roughness interface and texture models on friction angle between cohesive soils and steel, as well as abrasive paper material, using direct shear tests. All tests were carried out under consolidated drained shear conditions. The behavior at the soils–solid interface was found to vary according to surface roughness. It also seems that the type of material (steel or paper of abrasive) used does not have a major influence on the shear strength. As far as roughness is concerned, friction behavior is likely to be generally classified into three failure modes, namely full sliding at the interface, shear failure within the soil, and a mixed behavior where interface sliding and shear deformation of the soil specimen proceed simultaneously. However, for the second mode, the shear strength at the interface soil-rough solid materials steel was found to be lower than the shear strength of the soil, for a soil that is classified as high plasticity clay. Furthermore, it was found that the interfacial shear strength is independent of the texture surface for a given roughness. 相似文献
14.
Summary Direct shear tests were conducted on a granite to granite interface for the purpose of tracing the evolution of frictional resistance as the initially smooth and polished surface wears during continuing shearing displacement. At the moment when sliding on the freshly manufactured interface starts (first slip), the friction angle is very low, between 15° and 20°, but then it increases with displacement rapidly without reaching a peak in the first test (maximum displacement less than 25 mm). Upon repeated shearing of the same surface (without re-finishing), this process of displacement-strengthening continues until a total accumulated displacement of about one half of one meter is reached. At this point, the angle of friction would typically be between 42° and 44°.Once the residual surface was established, the effect of time-related parameters, the duration of stationary contact under constant normal and shear load and variable displacement rate, were investigated. The frictional resistance is shown to increase with decreasing displacement rate and to increase with the duration of stationary contact.At a normal load greater than about one half of one MPa, shear displacement on a residual surface proceeds in an unstable, stick-slip manner. The change from stable to unstable sliding, that can be effected by either decreasing the sliding velocity or increasing the normal load, is not instantaneous, but occurs over a finite amount of displacement. 相似文献
15.
目前,对于结构面的研究主要包括对剪切曲线形态的描述及结构面粗糙度、组数、充填物等因素对结构面强度参数的影响,一般情况下,这类研究的基础是结构面经受静荷载的作用。实际上,结构面也很容易遭受地震、水位升降、爆破等动力荷载的反复剪切作用,但是,至今对反复剪切作用下结构面力学特性的研究较少或缺乏系统性。笔者在室内直剪试验的基础上,研究了重复剪切作用下充填物对结构面变形和强度的影响。采用钢制模具和混凝土材料预制4种起伏角度结构面,在1.56MPa法向应力和两种充填状态下进行多次直剪试验,分析每次剪切过程中的切向应力和法向位移随切向位移的变化。通过对切向应力和法向位移随切向位移变化曲线分析可知,初次剪切时,起伏角度越大,结构面剪切破坏方式容易从滑移破坏过渡为剪断破坏;第二次剪切开始,无论起伏角度如何,结构面的剪切破坏方式基本上都转变为滑移破坏;充填物的存在基本不会改变结构面的剪切破坏方式,但会使剪切过程中结构面的爬坡效应增强,使结构面被剪断或磨损的作用减弱,峰值法向位移增大。 相似文献
16.
推移式滑坡演化过程模型试验与数值模拟研究 总被引：1，自引：0，他引：1
利用MTS电液伺服加载与控制系统对推移式滑坡物理模型后缘进行了分级推力加载,完成了推移式滑坡演化全过程的模拟。基于三维激光扫描技术对滑体表面的位移和变形进行了高精度、全方位、非连续性监测。采用多重分形基本理论对监测点云数据进行了系统分析,从试验的角度探讨了推移式滑坡演化过程中位移多重分形维数的变化特征。模型试验结果表明：推移式滑坡变形破坏以沿滑带发生的整体滑移为主,并表现出明显的演化阶段性特征,大致可划分为3个阶段：（1）后缘压缩阶段：滑坡模型表面变形体现为后缘土体的局部前移与隆起,整体变形小,多重分形维数成降维的特征,降维过程中未发生突变、有序性好;（2）匀速变形阶段：滑坡模型表面产生了明显的位移,变形不断向前和向两侧发展,前缘、中部滑体发生隆起现象,多重分形维数表现出先减后增的趋势;（3）加速变形阶段：滑坡模型表面体现出持续、快速、变化鲜明的整体变形特征,伴随出现滑坡模型中前部隆起带及横向、纵向的隆胀裂缝,多重分形维数成增维趋势。基于模型试验,利用FLAC3D进行了推移式滑坡演化过程的动态数值模拟,验证了滑坡演化的阶段性特征,揭示了推移式滑坡演化过程中稳定性系数非线性递减的规律。 相似文献
17.
合理桩间距的确定是抗滑桩设计的重要内容之一。认为抗滑桩的抗滑能力主要来自桩身迎荷面的阻滑能力和桩侧的阻滑能力这两个方面。在假定抗滑桩这两方面的阻滑能力均充分发挥的基础上,从桩侧摩阻力与桩后土拱极限剪切作用厚度范围内的摩阻力与拱后滑坡推力之间的静力平衡条件出发,基于Mohr-Coulomb强度准则,简化摩阻力的分布形式,建立悬臂式抗滑桩桩间距的计算公式。在此基础上,进一步研究了滑坡体的黏聚力、滑坡推力及抗滑桩的截面尺寸等因素对桩间距的影响。参数分析结果表明：桩侧阻滑能力在整个抗滑桩的抗滑能力中占有重要比例,且主要受桩侧面宽度控制;滑坡土体的黏聚力、内摩擦角,桩截面宽度等因素对抗滑桩最大桩间距具有较大程度影响。 相似文献
18.
《Engineering Geology》2002,63(1-2):169-185
Heavy rainfall from 26 to 31 August 1998 triggered many landslides in Nishigo Village of southern Fukushima Prefecture, Japan. The Hiegaesi landslide, a long-runout landslide with travel angle of 11°, which occurred in loamy volcanic-ash/pumice layer and was deposited in a nearby rice paddy, was investigated. In an observation pit dug in the middle part of the landslide deposit, the sliding zone just above the deflected rice plants was observed, and it was confirmed that grain crushing occurred in the sliding zone. The triggering and sliding mechanisms of this landslide then were investigated by ring-shear tests in laboratory. For the triggering mechanism, one saturated naturally drained test (test A: torque-controlled test) and one saturated undrained test (test B: speed-controlled test) were conducted on the samples taken from the source area of the landslide. Even in the naturally drained test opening the upper drain valve of the shear box, a temporary liquefaction occurred. In the undrained test, excess pore-pressure was generated along with shearing, and “sliding-surface liquefaction” phenomenon was observed. The effective stress and shear resistance finally decreased to near zero. These results can explain the observed phenomenon of small friction resistance like a flow of liquid when the sliding mass slid out of the source area. For the sliding mechanism of the landslide in the rice paddy, saturated undrained test (test C: speed-controlled test) was performed on soil sample above the deflected rice plants. The apparent friction angle obtained in this test was 8°. In addition, the residual friction angle measured after test B and test C was the same value of 41°. Combining with the observation on the shear zone in the ring-shear box after test C, it is concluded that, during the sliding in rice paddy, the undrained shear strength of the soil layer itself mainly influenced the high mobility of the landslide, probably because the friction between rice plants and soils is greater than the undrained shear strength inside the soil mass. 相似文献
19.
云南保山师专滑坡成因及防治 总被引：2，自引：0，他引：2
云南保山师专2001年7月发生中型滑坡，上千名师生的安全受到严重威胁。斜坡变形量逐渐加剧，1个月后总位移量近60cm，且前缘平台出现鼓丘，隆起高度1．20m。经采用袋装土反压前缘应急措施后，滑坡暂时得以控制。勘察发现滑坡的形成在于不合理的开挖边坡，其上软弱土体夹层经近期地震作用，经受超常强降雨持续渗入坡体，使之重度增加，强度降低，以及坡体上建筑物之荷载，增加了下滑力。滑坡防治采用抗滑桩加重力式抗滑挡墙，辅以地表、地下排水工程等综合治理方案。2002年9月治理工程全部完工，经监测证实治理效果良好。 相似文献
20.
Hossein Jalalifar Naj Aziz Muhammad Hadi 《Geotechnical and Geological Engineering》2006,24(5):1203-1227
Fully encapsulated rock bolting has, in recent years, become a universally accepted system of ground reinforcement in mining
and tunnel construction. The application of bolting systems extends both to rebar as well as cable bolting. The effectiveness
of the bolt application has been studied in shear, both by laboratory tests as well as by numerical modeling. A specially
constructed double shearing apparatus (DSA) was used to examine the shearing behaviour of a bolt installed perpendicularly
across two joints. The experimental study was complemented with three-dimensional numerical analysis. Parameters examined
include, the effect of reinforced material on tension/compression zones along the sheared bolt, shear resistance, shear displacement
and induced strains and stresses during bolt bending process. The study was undertaken at both free load and pretension conditions.
The conclusions drawn from the study were the level of bolt resistance to shear was influenced by bolt profile configuration,
the strength of the rock or medium influenced the level of load generated on the bolt and the increased bolt pretension contributed
to increased shearing load of the bolted medium. The numerical simulation of the bolt/medium interaction and deformational
behaviour were found to be in close agreement with the experimental test results. 相似文献