玛尔挡改线公路高边坡稳定性分析及生态治理

通过对玛尔挡改线公路高边坡工程地质及水文地质条件调绘探查、岩层节理裂隙统计,采用赤平极射投影法对边坡进行稳定性分析。分析结果显示,高边坡整体处于稳定状态,但如果不采取防护措施,边坡岩土层经过长期的风化剥蚀,边坡局部会逐渐趋于欠稳定状态。根据该地区气候、环境及以往经验,提出采用锚拉式混凝土挡墙结合柔性防护网的生态防护措施对边坡进行防护,实施效果良好。      

白鹤滩水电站左岸坝肩开挖边坡稳定性分析

白鹤滩水电站左岸坝基边坡地质构造错综复杂,坡内多条陡倾断层和顺坡向错动带是控制边坡稳定性的主要因素。结合现场地质资料、监测数据及勘察认识,利用通用离散元软件UDEC建立左岸边坡开挖变形分析模型。首先在无支护开挖工况下研究主要结构面F17、LS331、LS3319上下盘岩体关键点应力及位移变化,并指出潜在失稳破坏区;同时采用预应力锚索单元在不同施工时序下对潜在不稳定块体进行加固计算,对比研究了不同方案下左岸边坡的变形破坏机制和整体稳定性。计算结果和现场监测表明：左岸边坡变形破坏与结构面密切相关,在开挖卸荷作用下主要表现为沿错动带的压剪破坏和陡倾断层的张拉破坏,采用预应力锚索加固处理能够有效提高边坡稳定性,并且在开挖后及时跟进支护可以有效抑制边坡剪切变形。研究结果对白鹤滩左岸坝基边坡后续工程加固和施工工序具有一定的参考价值。     

坡顶荷载作用下岩质边坡弯曲倾倒破坏分析

车辆、坡顶堆载等造成的坡顶荷载是影响边坡稳定性的一个重要因素。首先,基于叠合悬臂梁模型和极限平衡理论,建立了坡顶荷载作用下岩质反倾边坡的力学分析模型,推导了坡顶荷载作用下边坡的剩余倾倒力和剩余滑移力计算公式,给出了岩层破坏模式判别条件,并通过大型数学分析软件Matlab将分析方法程序化;然后,通过与离散元模拟结果进行对比分析,验证了所提分析模型的准确性;最后,基于所提分析方法,进行了不同参数的敏感性分析。研究结果表明,坡顶荷载对岩层剩余力的影响较大,但对岩层破坏模式的影响不大;对边坡稳定性较为敏感的切坡角度为50°和岩层倾角为58°,当小于该值时,边坡稳定性将显著提高;层间黏聚力对自重边坡稳定性影响较大;数值模拟与理论分析得到的安全系数较为一致,验证了考虑坡顶荷载作用下弯曲倾倒破坏分析理论解的正确性,可为类似工程稳定性分析提供参考。     

含软弱夹层顺倾边坡爆破层裂效应的数值模拟与试验研究

进行含软弱夹层顺倾边坡单孔爆破数值模拟,分析爆破过程中上覆岩体受到的应力作用、爆破层裂效应及其对边坡稳定性的影响。模拟结果表明,爆破层裂作用具有分区特性,爆轰气体对夹层的冲刷、推移作用形成夹层爆腔区,爆腔区外围是压密区,其次是离析区,离析区以外的夹层未受爆破层裂作用的影响;上覆岩体在空腔区受到爆轰气体膨胀压力作用,临近夹层壁面的峰值压力达0.75 GPa,压密区受到夹层挤压衍生的向上压力作用,压力峰值达0.21 GPa,且压力衰减较慢;空腔区的上覆岩体与夹层脱离,压密区和离析区改变了夹层与上覆岩体的接触状态,使模型的稳定性降低。剪切试验验证了数值模拟关于爆破层裂效应降低模型稳定性的结论。     

Effect of rock mass disturbance on the stability of rock slopes using the Hoek–Brown failure criterion

The process of creating man made or “cut” slopes in rock invariably leads to stress relief within the rock mass which in turn induces a certain degree of fracturing and disturbance. The level of disturbance can be particularly significant when the slope is formed using blasting techniques. However, the effects of this disturbance on the overall rock slope stability have not been investigated thoroughly in the current literature. In order to account for rock mass disturbance during construction, a disturbance factor has been included in the Hoek–Brown failure criterion [1]. This paper uses finite element upper and lower bound limit analyses to estimate rock slope stability based on the Hoek–Brown failure criterion whilst including the effect of rock mass disturbance. A rigorous set of analyses have been performed where the level of disturbance is considered as constant or linearly varying throughout the slope. The results are then compared to a number of reported case histories for verification purposes. From the results of this study, the disturbance factor was found to have significant influence on the rock slope stability assessment, especially for poorer quality rock masses. Hence, cautious engineering judgement must be exercised when estimating the level of disturbance. In addition, utilising stability charts to estimate the stability of cut rock slopes without considering the rock mass disturbance may lead to significant overestimations.     

Rock slope stability assessment using finite element based modelling – examples from the Indian Himalayas

Numerical modelling of rock slides is a versatile approach to understand the failure mechanism and the dynamics of rock slopes. Finite element slope stability analysis of three rock slopes in Garhwal Himalaya, India has been carried out using a two dimensional plane strain approach. Two different modelling techniques have been attempted for this study. Firstly, the slope is represented as a continuum in which the effect of discontinuities is considered by reducing the properties and strength of intact rock to those of rock mass. The equivalent Mohr-Coulomb shear strength parameters of generalised Hoek-Brown (GHB) criterion and modified Mohr-Coulomb (MMC) criterion has been used for this continuum approach. Secondly, a combined continuum-interface numerical method has been attempted in which the discontinuities are represented as interface elements in between the rock walls. Two different joint shear strength models such as Barton-Bandis and Patton’s model are used for the interface elements. Shear strength reduction (SSR) analysis has been carried out using a finite element formulation provided in the PHASE². For blocky or very blocky rock mass structure combined continuum-interface model is found to be the most suitable one, as this model is capable of simulating the actual field scenario.     

The Dynamic Evaluation of Rock Slope Stability Considering the Effects of Microseismic Damage

A state-of-the-art microseismic monitoring system has been implemented at the left bank slope of the Jinping first stage hydropower station since June 2009. The main objectives are to ensure slope safety under continuous excavation at the left slope, and, very recently, the safety of the concrete arch dam. The safety of the excavated slope is investigated through the development of fast and accurate real-time event location techniques aimed at assessing the evolution and migration of the seismic activity, as well as through the development of prediction capabilities for rock slope instability. Myriads of seismic events at the slope have been recorded by the microseismic monitoring system. Regions of damaged rock mass have been identified and delineated on the basis of the tempo-spatial distribution analysis of microseismic activity during the periods of excavation and consolidation grouting. However, how to effectively utilize the abundant microseismic data in order to quantify the stability of the slope remains a challenge. In this paper, a rock mass damage evolutional model based on microseismic data is proposed, combined with a 3D finite element method (FEM) model for feedback analysis of the left bank slope stability. The model elements with microseismic damage are interrogated and the deteriorated mechanical parameters determined accordingly. The relationship between microseismic activities induced by rock mass damage during slope instability, strength degradation, and dynamic instability of the slope are explored, and the slope stability is quantitatively evaluated. The results indicate that a constitutive relation considering microseismic damage is concordant with the simulation results and the influence of rock mass damage can be allowed for its feedback analysis of 3D slope stability. In addition, the safety coefficient of the rock slope considering microseismic damage is reduced by a value of 0.11, in comparison to the virgin rock slope model. Our results demonstrate that microseismic activity induced by construction disturbance only slightly affects the stability of the slope. The proposed feedback analysis technique provides a novel method for dynamically assessing rock slope stability and can be used to assess the slope stability of other similar rock slopes.     

A new slope mass rating in mountainous terrain, Jammu and Kashmir Himalayas: application of geophysical technique in slope stability studies

The slopes of western Lesser Himalaya (at Sangaldhan Block of Udhampur near Ramban, Jammu and Kashmir India) are being severely affected by tectonic and erosional activities. These activities result in deposit of a thick cover of rock fragments and overburden just above the hard rock. The thickness of overburden cover has directly affected the stability of slope in the study area, though the traditional stability estimation techniques, rock mass rating and slope mass rating, rate this area as moderately stable which does not represent the real stability condition. In this research work, the geotechnical and geophysical surveys have been carried out to reckon the slope stability conditions more accurately as compared to traditional slope stability estimation techniques. A new rating, new slope mass rating, is developed, which gives a better picture of the stability of slopes. It incorporates a new parameter of overburden thickness profile, along with slope angle and other associated factors on the slopes of the mountainous terrains. The vertical electrical sounding surveys were conducted for the demarcation of rock–overburden interface and for determining the overburden cover. This new classification depicts an increase of 12.84 % in unstable slope areas giving a better assessment and factual picture of slope stability in our study area. This study also enumerates the importance of geophysical applications in slope stability studies. The research work is applicable in mountainous terrains such as Himalaya, and the major component of the application is the orientation of overburden or the profile of thickness in relation with slope of surface.     

滑坡及危岩(崩塌)防治工程措施选择与工程设置

滑坡和危岩（崩塌）治理工程措施较多，措施组合可变性大，每种工程措施都有其相应的应用条件，不宜性、适宜性和最佳配置组合。治理工程措施选择应充分考虑治理工程功能性的具体要求、在不同工况条件下的安全性及耐久性、工期要求和投资的经济性以及后期维护的要求、工程岩土体性质及其蓄水后的变化、场地条件、施工技术条件、地方材料资源等具体制约因素以及环境保护的要求。在三峡水库区二期地质灾害防治工程国家级验收总结的基础上，对滑坡与危岩（崩塌）常用防治工程措施（排水、削方减载、回填压脚、抗滑桩、重力式抗滑挡墙、预应力锚索、格构锚固、拦石墙等）的工程适用条件、工程设置及不宜性进行了详细的分析，并提出工程设置应考虑及注意的问题。     

缓倾层状结构高陡采动斜坡变形特征研究

采空区深度、平面位置等控制缓倾层状结构采动斜坡的变形特征,直接影响采动斜坡整体稳定性。近年来,国内外学者针对地下采煤引起上覆岩体变形开展了大量研究,但目前采空区特征对斜坡关键位置的影响作用揭示还不够深入。贵州省发耳煤矿尖山营变形体是典型的缓倾层状结构采动斜坡,具有上陡下缓、上硬下软的特征。文章以发耳尖山营变形体为例,采用地质过程机制定性分析和数值模拟方法研究了多层开采与不同深度单层开采对斜坡变形的影响,揭示采空区宽度、深度及深厚比等参数对斜坡变形特征的影响。结果表明:多层开采导致斜坡坡脚破坏和整体塌陷,引起斜坡产生显著向坡外的水平位移,导致竖向位移远大于煤层开采总厚度;采空区跨越坡脚致使开采深厚比急剧减小,采动裂隙更易扩展至地表,是坡脚附近岩体产生破坏的重要因素;采空区宽度增大、多层采动会显著加剧斜坡变形,采空区深度增加可减小斜坡变形量值,但显著增加变形范围。在地形起伏强烈地区采煤,通过优化工作面布置,防止开采深厚比急剧减小、控制采空区宽度、避免重复采动以及开采更深部煤层对斜坡稳定性有利。     

基于离散元法的节理岩体边坡稳定性分析

节理岩体边坡的稳定性在很大程度上取决于节理的强度及其分布形式。由于节理岩体边坡的失稳破坏具有大变形和非连续的特点,因此,离散单元法成为研究节理岩体边坡破坏机制的最有效方法之一。通过采用离散元软件PFC2D进行数值模拟,对完整岩石及节理的力学性能进行研究,并建立含密集节理的岩体边坡模型,讨论了节理连通率对边坡破坏形式的影响。结果表明,节理岩体边坡的失稳破坏是一个渐进的过程;在多组节理密集分布的岩体边坡中,连通率越大,其稳定性越差;随着连通率的减小,边坡的破坏形式由大范围的滑坡转变为局部崩塌的形式     

四川省理县—小金公路岩质边坡监测试验研究

根据在四川省理县—小金路震区边坡开展的边坡现场监测试验,并结合监测期间区域范围内发生的三次48级以上地震,表明:表面岩体结构面总体出现了一个变形量迅速增大的过程,其施工对震区岩质边坡坡面产生的松散变形影响依然是最大的,施工后坡面在经历2个月的变形衰减后,基本趋于稳定;对于该处边坡的反向结构面,地震还将对坡表岩体结构产生一个挤密的变形作用,这有利于坡表岩层的稳定性;水平位移变化频繁,与该处位置及其荷载、地震激发等因素相关。在该处下边坡设立挡土墙是十分必要的,其后期的观测数据表明该处已基本恢复稳定。     

水布垭马崖高边坡岩体地下开挖三维数值模拟研究

清江水布垭水电站是清江上游拟建的一个特大型水电工程,马崖高边坡位于水布垭峡谷出口右侧,总体地质结构具上硬下软特征,电站导流洞及尾水洞将从马崖高陡边坡坡脚穿出,地下开挖主要在软岩层中。应用FINAL及ROCKY程序对水布垭马崖高陡边坡岩体地下开挖进行数值模拟,研究了边坡岩体内进行地下洞室开挖后边坡力学状态的改变及洞室岩体（含岩柱）的稳定性,基于削坡是水布垭马崖高陡边坡的重要整治措施之一,研究中进行了各种分步开挖工况下的削坡有效性定量研究,重要工况还同时进行了VI度地震作用下的动力作用分析。     

Rock slopes risk assessment based on advanced geostructural survey techniques

The rock mass structure determines the possible unstable blocks that can induce rock fall phenomena. The stability analyses must therefore be based on an accurate geo-structural survey. In this work, the stability conditions of several steep slopes along a motorway in the Far East have been evaluated through key block analysis based on traditional surveys and on laser scanner acquisitions. Discontinuity orientations and positions on the rock face are derived from the point cloud in order to perform the reconstruction of the rock mass and to identify blocks in the slope. Results obtained from both the traditional and the new method is in good agreement. Stability analyses have been performed for evaluating the kinematic feasibility of different failure mechanisms. The rock block shapes and volumes are computed by performing 2D and 3D analyses whereas the failure mechanisms are examined using the key block method. Parametrical analyses have been carried on to evaluate the influence of slope angle variation. DEM models have also been set up. The relative hazard is determined by statistically evaluating the kinematical feasibility of different failure mechanisms. Hazard mapping has been utilized to identify the best methodology for risk mitigation.     

Discontinuity controlled probabilistic slope failure risk maps of the Altindag (settlement) region in Turkey

The evaluation of potential rock slope problems using stereographic projection techniques known as kinematic analysis is one of the most important parts of a slope stability investigation to be carried out in jointed rock media. In conventional stereoprojection techniques for the assessment of possible rock slope failures, the peak orientations of joints together with the slope geometry and the friction angle of the weakness planes are used. Other possible joint orientations which may be encountered in the rock media are ignored, although they belong to the group of joint peak orientations. In this study, nearly vertical jointed andesites cropped out at the Altindag settlement region in Ankara were studied in order to evaluate the relevance of this ignored discontinuity orientation data on slope stability. As a result, probabilistic risk maps for planar, toppling and wedge failures were produced using the kinematic rules and digital elevation model of the study area. The comparison of the distribution of the actual failures in the area and the probabilistic risk maps prepared for the study area revealed that all of the identified failures are found to be located in the higher risk zones on the probabilistic risk maps.     

顺向岩质高边坡分级开挖的变形破坏特征研究

以岩质高边坡的野外调查成果为基础,分析了边坡的岩体结构特征和控制边坡稳定性的主要地质要素,依据自然边坡的变形破坏现状定性分析,预测边坡开挖过程中可能出现的宏观变形破坏模式和特征.利用基于有限差分原理的FLAC3D建立坝肩边坡的地质模型,对工程边坡开挖支护过程进行数值法定量研究,得出了工程边坡开挖过程中的应力、位移变化规律和边坡岩体破坏特征.研究成果为苗家坝水电站左坝肩的分级开挖施工提供了依据.     

考虑突变理论的顺层岩质边坡失稳研究

应用突变理论,以顺层岩质边坡为例,考虑地下水对滑面带介质的应变和水致弱化性质,以及地下水对边坡后缘张裂缝的水力效应,构建了边坡的尖点突变模型,分析了顺层岩质边坡失稳的力学机制：边坡失稳过程主要是内部因素和外部因素共同作用的结果,内部因素主要是地下水通过物理化学作用软化了滑面带岩体,使滑面带岩体刚度比降低,在边坡失稳的过程中起主导的定性作用;外部因素主要是指边坡后缘张裂隙的静水压力,不仅使得边坡的滑动势能增加,还对边坡造成一种扰动的作用,加速滑坡的启动。在突变分析的基础上,推导了边坡后缘张裂缝临界充水高度和临界降水强度的关系式,建立了边坡滑移破坏的水力判据;给出了边坡岩体在渐进软化过程中的位移变化规律,剪切位移并非均匀增长,而是呈现出阶梯状跳跃式上升。同时,进行了室内物理模型试验（当刚度比 ）,在一定程度上验证了考虑突变理论来分析顺层岩质边坡失稳的力学机制和边坡岩体在渐进软化过程中位移变化规律的合理性。并提出了此种类型边坡的处治技术与优化方法建议。     

基于结构面性状对岩体力学性质响应的模拟研究

为研究结构面性状对锦屏大奔流料场边坡岩体性质的影响,在对该边坡砂岩进行室内三轴压缩试验的基础上,开展含4组不同结构面性状岩体的力学模拟测试,最后对该边坡岩体的开挖进行数值模拟。试验结果表明,岩样破坏过程可以分为4个典型的阶段: 弹性变形阶段,屈服阶段,残余强度阶段及塑性流动阶段。随着围压的增大,岩石破坏所需偏应力逐渐增大,且岩石逐渐表现出延性特征。结构面性状模拟结果表明,含软弱充填结构面比不含者对岩体力学性质影响(弱化)大,有倾角结构面比无倾角结构面对岩体性质影响较大,大倾角结构面总体上比小倾角的影响大,软弱充填厚度对岩体内摩擦角影响较大。实例模拟结果表明,开挖卸荷使得边坡后缘岩体产生卸荷回弹变形,产生X向拉伸位移,煌斑岩脉的存在使得塑性区域沿此软弱带发展,开挖第8步时,塑性区贯通,边坡发生失稳。研究结果对陡高边坡岩体开挖的稳定性评价具有一定指导意义。     

基于参数反演的边坡地下水渗流数值模拟

渗流是影响岩土工程边坡稳定性的重要因素,对不同工况下岩土体边坡地下水渗流规律进行数值模拟,弄清其动态变化规律,对于边坡稳定性分析、支护设计、工程防排水措施的制定等都有重要的意义。以龙滩水电站左岸进水口边坡为研究对象,通过免疫进化规划算法,得到了边坡岩体渗流场参数。在此基础上,对洪水期、枯水期情况下地下水渗流状态进行了数值模拟,通过对比分析,研究了不同河床水位情况下地下水渗流变化规律,从而为边坡稳定性预测奠定了理论基础。     

基于节理不确定性的可靠度分析

边坡稳定性一直是边坡安全的重点研究对象,针对边坡评价中常见的不确定性因素,可靠度分析是值得利用的方法。为评价某节理发育的岩质岸坡稳定性,通过有限元计算软件,结合现场勘探测绘数据,建立以边坡节理强度参数c、φ为输入变量,安全系数为输出变量的点估计（PEM）计算概率模型,计算结果表明:节理发育对该边坡变形具有明显控制作用;边坡整体可靠性较好,破坏概率极低。最后,通过蒙托卡罗法对可靠度结果进行验证,结果表明两种方法的计算结果不存在显著性差异。研究结果表明节理对岩质边坡稳定具有良好的敏感性,基于节理不确定性的点估计法分析边坡可靠度是一种有效的方法。