三峡永久船闸高边坡关键块体的概率分析(英文)

基于传统块体理论对不连续岩体的稳定分析是建立在不连续面贯穿所研究岩体的假定基础上的，而实际的岩体不连续而长度是有限的。因此，本文将随机概率模型张块体理论，研究了三峡永久船闸边坡关键块体的肖落概率和块体的大小及分布密度，结果表明该方法具有重要的工程实用价值。     

Evaluation of rock slope stability for Yujian River dam site by kinematic and block theory analyses

Lithological information, rock mass fracture data and discontinuity shear strength obtained through field investigations have been used to conduct kinematic and block theory analyses for the rock slopes that exist in the dam site to evaluate the stability of the slopes. The analyses were performed using mean discontinuity set orientations for each rock mass region under gravitational loading to calculate the maximum safe slope angles (MSSA) for different cut slope directions. Results show that final MSSAs obtained from kinematic analysis are less than or equal to that obtained from block theory analysis. The following conclusions have been made based on the block theory analysis results, which are closer to the reality: (1) The final MSSA range between 30° and 47°, 44° and 70°, 47° and 69° for cut slope dip directions of 20–30°, 105–210°, and 270–355°, respectively; (2) For cut slope dip directions of 20–30°, 200–210° and 275–315°, wide ranges of values have been obtained for the final MSSA reflecting the influence of variability of fracture orientations on MSSA; (3) Apart from the region R-d-1 for slope dip directions in the range 20–30°, rest of the regions at the dam site seem to be stable for slope angles less than 40°. Detailed comparisons are given between the kinematic and block theory analyses covering both the theoretical concepts and application results. Also a brief comparison is included between the laboratory and in situ discontinuity shear strength results.     

Cut Slope Design Recommendations for Sub-Horizontal Hard Sedimentary Rock Units in Ohio, USA

Although most cut slopes in Ohio consist of inter-layered, sub-horizontal units of hard and soft sedimentary rocks (sandstone, limestone, dolostone, shale, claystone, mudstone), slopes consisting of relatively thick hard rock units are not uncommon. Design of stable cut slopes in hard rock units needs to consider rock mass strength and orientation of discontinuities with respect to slope face. Results of kinematic stability analyses show that hard-rock cut slopes are less likely to have conventional plane and wedge failures, caused by unfavorable orientation of discontinuities. The main cause of failure is identified to be the undercutting-induced toppling, which is not amenable to traditional kinematic or rock mass strength-based analyses. Therefore, to recommend a suitable slope angle, numerical models, using UDEC software, were employed to study how various slope angles affect the process of undercutting-induced toppling failures. The UDEC models showed a slope angle of 45° (1H:1 V) to be the most stable angle. However, a 63° (0.5H:1 V) slope angle can significantly reduce the potential for such failures and is therefore more appropriate than the widely used angle of 76° (0.25H:1 V).     

三峡工程船闸高边坡岩体稳定性预测方法研究

三峡船闸高边坡岩体稳定性主要影响因素为结构面发育情况。施工期地质超前预报,着重从结构面网络角度进行处理,其方法为：编录统计整理结构面,建立高边坡的三维立体网络图形;岩体质量分析,进行概率模型与确定性模型的耦合模拟;块体判断分析,对临空面块体、内部块体进行判断、搜索、分析;稳定性计算分析。     

三峡船闸高边坡预应力锚索耐久性研究

三峡双线五级船闸高边坡工程共安装了1 000 kN预应力锚索229束,3 000 kN预应力锚索3 975束,400 kN高强锚杆9.7万根,加固岩石边坡楔形块体1 054个,完成的边坡锚固量和岩石块体支护量均属世界之最。由于预应力锚索在船闸高边坡中起着至关重要的作用,在船闸预应力锚索设计和施工过程中对锚索的防腐措施进行了系统研究,并收集国内外锚索耐久性研究最新成果,结合船闸锚索的地下环境对锚索耐久性进行了全面研究。研究成果显示,三峡船闸高边坡预应力锚索防腐措施可靠,耐久性可以保证。     

Modeling progressive failures in rock slopes with non‐persistent joints using the numerical manifold method

Rock slope failure is a complex process that usually involves both opening/sliding along pre‐existing discontinuities as well as fracturing of intact rock bridges. Discontinuity persistence is an important factor governing rock slope instabilities. However, traditional slope failure analysis assumes persistent discontinuities, and rock slope fails along a predefined persistent continuous potential failure surface because of the limitations of the analysis tools. This paper proposes the numerical manifold method (NMM) incorporated with a Mohr–Coulomb criterion‐based fracturing algorithm to simulate the progressive failure of rock slopes with non‐persistent joints. Detailed fracturing algorithm is first presented. Then, the NMM enabling fracturing is calibrated through simulating an edge‐cracked plate and the Brazilian test. Lastly, the developed code is applied to investigate the failure process of rock slopes involving non‐persistent joints. Numerical results indicate that the proposed method can capture the opening/sliding along existing discontinuities, the fracturing in intact rock bridges and the final kinematic release. Progressive slope failure is well exhibited. Copyright © 2013 John Wiley & Sons, Ltd.     

缓倾外层状结构边坡变形破坏模式及支护对策研究

高速公路开挖形成越来越多的工程边坡。缓倾外层状结构边坡作为一种典型的岩质边坡,一般情况下整体稳定性较好,但在特定的结构面组合状况下,开挖后也可能产生整体变形破坏。本文以软弱结构面和长大裂隙发育的公路工程边坡为例,通过岩体结构及边坡一定范围内已有边坡破坏现象的调查研究,采用工程地质类比和三维离散元法综合分析边坡变形破坏模式,并针对变形破坏模式的特点,提出支护对策。研究结果表明,结构面贯通坡体形成切割块体的后缘和侧缘边界时,缓倾外层状结构边坡可沿层面产生滑移-拉裂变形,若滑面与临空面具有一定夹角,边坡的变形可表现为旋转式滑移-拉裂;结构面组合控制的缓倾外层状结构岩质边坡稳定性受坡体中下部的关键块体控制,一旦关键块体失稳,将引起上部块体的连锁失稳,此类边坡变形控制的重点是对关键块体分布区域进行强支护;支护工程实施后的变形监测结果表明,基于变形破坏模式分析的边坡支护方案保证了边坡施工和运营过程中的安全。     

Influence of discontinuities and clay minerals in their filling materials on the instability of rock slopes

To assess the influence of discontinuities and clay minerals in their filling materials on the instability of rock slopes, seven rock slopes along the margin of Ganjnameh–Shahrestaneh Road, Hamedan Province, Western Iran were selected, and the physical and mechanical properties of their rocks and discontinuities were determined. By statistical studies of the discontinuities, rock slope stability analysis has been performed using kinematic and limit equilibrium methods so that safety factors for the rock slopes can be calculated. Also, sampling of filling materials and X-ray diffraction tests have been done to identify the clay minerals in the filling materials. The lithologies of the studied rock slopes are granite, diorite and hornfels. The presence of discontinuities and weakness planes with different orientations and clay minerals in filling materials of discontinuities are effective factors that cause plane, wedge and toppling failures in the rock slopes. Clay minerals as filling materials of discontinuities in the studied rock slope facilitate their instability by two different methods. First, absorption of water by infilling clay minerals causes the friction angle of discontinuity surfaces that leads to plane and wedge failures to be reduced. Second, water absorption causes the swelling of clay infilling minerals that leads to toppling failure.     

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.     

汤屯高速公路某变质砂岩边坡块体稳定性评价

汤屯高速公路存在大量变质砂岩组成的高边坡,岩体质量一般较好,但结构面发育,组合形成大量潜在失稳块体,这些块体的稳定性状况直接影响边坡安全.本文选取一个典型边坡,通过对边坡结构面详细地质素描,查明构成可能失稳块体的边界条件,并利用块体理论对可能失稳的块体在各种工况下的稳定性进行计算,并结合块体工程特性,对边坡的稳定性进行系统评价.该研究成果对该边坡的支护优化设计提供了基础资料,同时对同类型的边坡设计具有一定的指导意义.     

Numerical Modelling of Steep Slopes in Open Rock Quarries

The key question regarding steep rock slopes along rock quarries is their stability because a rock slope failure can have critical results. In this study, the aim is to investigate the areas with potential risk for jointed karstic limestones in a rock quarry. First, to determine rock mass properties, scan-line surveys were performed, and the major orientations of discontinuities were analyzed using stereographic projection. Then, the physicomechanical properties of the slope-forming rock were determined in the laboratory, and geomechanical properties of the rock mass were determined using an empirical failure criterion. Finally, the quarry slope stability was assessed in accordance with numerical modelling. According to the results obtained, the numerical modelling of steep rock slopes can be efficiently evaluated by using finite element method. Beside this, the presence of joints intersecting the main discontinuity sets, the filling materials of discontinuities resulting from weathering of limestone and surface deposits, surcharge load due to mine waste dumped on the slopes and excavation blasting during construction of quarry area play a key role when modelling the steep rock slopes by using finite element method.     

Stability analysis of rock slopes along Gangadarshan,Pauri, Garhwal,Uttarakhand

The rock mass rating (RMR) and slope mass rating (SMR) has been carried out to classify the slope in terms of slope instability. To understand the RMR and SMR various geostructural, geomorphologic and hydrological parameters of the slopes were measured and analyzed. 32 rock slopes/rock cum debris slopes were identified in the study area. The present RMR and SMR study is an outcome of extensive field study along a stretch of about 10 km on road leading from Srinagar to Pauriarea along Alaknanda valley. The technique followed incorporates the relation between discontinuities and slope along with rock mass rating (RMR) and slope mass rating (SMR). The analysis of the 32 studied slopes shows that in the Gangadarshan area out of six rock slope facets, two falls in class II (stable) and four in class IV (unstable). It is significant to note that the slope facets coming under class IV are comprised of active landslide portions. While the slopes under class II show minor failure or old landslide debris.     

Optimization of slope angle of a lead-zinc mine

Summary The present study represents an attempt to optimize the overall slope angle of a lead-zinc mine in Rajasthan state, which could extend to a depth of 170 m during the first phase of mining. Detailed geotechnical investigations were conducted. These included geotechnical mapping, determination of the physio-mechanical properties of intact rock, determination of the rock mass rating and estimation of rock mass properties. Information was collected from mapping of benches and borehole logs. Based on these data, limit equilibrium and numerical simulation techniques were applied in order to assess the stability of the slopes and determine an optimum slope angle. From these investigations it has been inferred that the overall footwall and hangingwall slopes should be 42° and 48° respectively.     

Assessment of excavatability,abrasivity and slope stability in a sandstone quarry in Istanbul,Turkey

The Cebeci region is characterized by outcrops of Carboniferous sandstone, including diabase dykes. This region is very important area for aggregate production in Istanbul, Turkey. The aim of this study is to determine the engineering geological properties of sandstones to assess the excavatability, abrasivity and stability of cut slopes in a quarry site. Firstly, the sandstone samples were used to determine their petrographical and mineralogical characteristics. Then, physico-mechanical tests were performed on these samples. In order to determine rock mass properties, scan-line surveys were performed, and the major orientations of discontinuities were analyzed through the stereographic projection technique. Kinematical analyses were also made to determine the potential failures at the quarry site. According to the results obtained, excavatability is changed from easy ripping to hard ripping on sandstones; the carbonated sandstone is less abrasive than other sandstones. Based on the field studies and stability analyses of the cut slopes, optimum slope geometry and necessary support measures, such as wire mesh and rock fall barriers, are suggested.     

Plane failure analysis of rock slopes

Summary Hoek and Bray (1981) gave an analytical approach for plane failure analysis for rock slopes that is limited to those slopes in which the upper slope surface is horizontal and the tension crack is vertical. An analysis is presented here which can take these factors into account. It is found that varying the angle of the upper slope from 0° to 30° causes a significant reduction in the factor of safety. Varying the tension crack from vertical to 70° only has an effect when the upper slope angle is less than 20°.     

A resilience framework for safety management of fossil fuel power plant

In the present study, cut slope stability assessment along ghat road section of Kolli hills was carried out by using various geotechnical parameters of rock and soil slope sections and structural kinematics of major discontinuities is presented. The rock slope (RS) stability assessment was carried out using Rock Mass Rating basic (RMR_basic) and Slope Mass Rating (SMR) classification systems. The type of failure and their Factor of Safety (FOS) for individual RS was calculated using Hoek and Bray method. In the case of soil slopes (SS), the FOS was calculated using Circular Failure Chart (CFC) and Limit Equilibrium (LE) methods. The input data for the slope stability analyses were collected through extensive field work followed by stereonet plotting and laboratory test. There are six rock slope sections, and five soil slope sections were taken into consideration for the cut slope stability analyses. The area depicts class II (RS-1, 2, & 6) and class III (RS-3, 4, & 5) of RMR classes. The SMR result depicts for RS-1, RS-2, and RS-6 are 64.40, 60.02, and 60.70, respectively, and falls in class II stable condition. The SMR values of RS-3 and RS-5 were 44.33 and 57, respectively, and come under the class III partially stable condition. The RS-4 with SMR value of 17.33 falls under the class I completely unstable condition. The FOS of planar failure case indicates that RS-3 (FOS = 0.22) is more unstable, while all other sections are having greater than 1 FOS. The calculated FOS values using CFC method reveals that the FOS is very close to 1 for all the SS sections that fall under completely saturated condition which indicates that these slope sections may fail during heavy rainfall. In LE method, the sections SS-3 and SS-4 are unsafe under partially and completely saturated (natural slope) condition. In average slope condition, all the SS sections are unsafe under partially or completely saturated conditions. The facets 2, 3, 4, and 5 required mitigation measures, to improve the stability of slopes. Site-specific mitigation measures were suggested for partially or completely unstable rock and soil cut slopes.     

高陡岩质料场边坡稳定性与支护设计研究

水电站料场高边坡具有高度大、坡度陡、卸荷速度快等特点,因多按临时边坡进行设计,故施工期变形破坏事例频发。基于这一现状,依托瀑布沟水电站两岩质料场边坡,通过两年多跟踪施工过程的支护设计工作,总结出一套操作性强的料场高边坡稳定性及支护设计方法。针对料场边坡存在的受软弱结构面控制的边坡整体稳定性、浅表层块体稳定性、碎裂岩体稳定性三种工程地质问题,在跟踪施工过程开展岩体结构调查的基础上,按照先整体后局部的稳定性评价思路,开展高边坡稳定性评价。施工期动态支护设计按照保证整体稳定,控制局部变形,顾全潜在失稳区域的理念,通过定性评价确定不稳定区域并优先设计提交施工;针对施工中最易出现的块体变形和碎裂岩体变形,建立了合理的支护设计原则和严格的施工规定;对稳定性差、施工风险高、支护造价大的潜在不稳定区域,应及时地调整开挖方案,减少工程造价。实践表明,这套方法保证了料场高边坡的快速施工安全,减少了工程投资。     

双临空面岩质边坡滑动与倾倒破坏的运动学分析

临空面的几何形状在边坡破坏模式与稳定性分析中起着举足轻重的作用。运动学分析是确定边坡破坏模式与评价边坡稳定性的一种有效方法。目前基于运动学分析的边坡稳定性研究主要集中于单临空面边坡的破坏模式与最大安全开挖边坡角的确定。本文将此项研究扩展至双临空面边坡,将其破坏模式细分为4种,分别为沿结构面发生单平面滑动、沿结构面发生楔形体滑动、沿两个结构面的交线发生楔形体滑动以及倾倒破坏。在立体投影中得出,平滑滑动与楔形体滑动的滑动区为双临空面真倾向线与摩擦圆所组成的区域,单个结构面倾角矢量与两个结构面交线矢量位于该区城内;倾倒破坏区为双临空面真倾向线、摩擦圆与基圆所组成的区域,结构面的法向矢量位于该区城内。提出了双临空面边坡最大安全开挖边坡角的确定方法及边坡设计原则。最后将上述方法应用于三峡库区湖北省秭归县郭家坝镇郭家坝村生基坡高边坡,研究了该双临空面边坡的破坏模式并给出了最大安全边坡角的建议值     

Terrestrial Photogrammetry and Numerical Modelling for the Stability Analysis of Rock Slopes in High Mountain Areas: Aiguilles Marbrées case

Several high-altitude slope instability phenomena, involving rock blocks of different volumes, have been observed in recent years. The increase in these phenomena could be correlated to climatic variations and to a general increase in temperature that has induced both ice melting with consequent water seepage and glacial lowering, with a consequent loss of support of the rock face. The degradation of the high-altitude thermal layer, which is known as “permafrost”, can determine the formation of highly fractured rock slopes where instabilities can concentrate. The present research has developed a methodology to improve the understanding and assessment of rock slope stability conditions in high mountain environments where access is difficult. The observed instabilities are controlled by the presence of discontinuities that can determine block detachments. Consequently, a detailed survey of the rock faces is necessary, both in terms of topography and geological structure, and in order to locate the discontinuities on the slope to obtain a better geometric reconstruction and subsequent stability analysis of the blocky rock mass. Photogrammetric surveys performed at different times allow the geostructure of the rock mass to be determined and the rock block volumes and detachment mechanisms to be estimated, in order to assess the stability conditions and potential triggering mechanisms. Photogrammetric surveys facilitate both the characterisation of the rock mass and the monitoring of slope instabilities over time. The methodology has been applied in a case study pertaining to the North Face of Aiguilles Marbrées in the Mont Blanc massif, which suffers from frequent instability phenomena. A slope failure that occurred in 2007 has been back-analysed using both the limit equilibrium method (LEM) and 3D distinct element modelling (DEM). The method has been supported and validated with traditional in situ surveys and measurements of the discontinuity orientation and other rock mass features.     

岩质边坡复合型破坏机制的改进运动单元法研究

目前运动单元法的研究主要集中于土质边坡,未涉及到岩质边坡稳定性分析问题;而岩体中孕育有不同特性的结构面,控制着岩质边坡的力学行为。为求解结构面控制作用下岩质边坡“结构面滑移-岩桥剪断”复合型破坏问题,研究了塑性滑移区节点在岩桥内和结构面上的运动约束条件,推导了含结构面的运动单元计算公式,提出了改进运动单元法。通过经典算例的对比分析,验证了改进运动单元法计算结果的准确性。研究结果表明:岩桥位置、结构面贯通度和结构面倾角是控制岩质边坡力学行为的3个主要影响因素。岩桥越接近坡顶,改进运动单元法所得安全系数越大,而Jennings法无法反映岩桥位置的影响效应。高贯通度的结构面导致岩质边坡发生“结构面滑移-岩桥剪断”复合型破坏模式,安全系数较小;而低贯通度的结构面导致完整岩石发生破坏,安全系数较大。水平或陡倾角结构面导致滑裂面穿切结构面,安全系数较大;而对于其它倾角情况下的结构面,岩质边坡发生“结构面滑移-岩桥剪断”复合型破坏模式,安全系数较小。实例应用结果说明该方法可以有效评价岩质边坡的稳定状态,可在类似工程中应用推广。