A Dynamic Comprehensive Method for Landslide Control

A slope failure is developed due to progressive external loads and deteriorations of slope geomaterials, thus forming a progressive and dynamic development and occurrence of landslides. Site geological properties and other active factors such as hydrodynamic load and human activities are complex and usually unknown, thus this dynamic development and occurrence of landslides can only be understood through the progressive accumulation of knowledge on the landslides. For such a progressive process, this paper proposes a dynamic comprehensive control method for landslide control. This control method takes full advantage of updated monitoring data and site investigations of landslides, and emphasizes the implementation of possible measures for landslide control at reasonable stages and in different groups. These measures are to prevent the occurrence of a landslide disaster. As a case study, a landslide project at the Panluo open-pit iron mine is analyzed to illustrate this dynamic comprehensive control method.

Preliminary Analysis on the May 1st Landslide at Wulong

分析了边坡工程地质条件和地质成因机制；根据现场调查数据建立了滑坡地质剖面,反演了滑坡发生时滑动面的抗剪强度参数；分析了原坡形及降雨所引起孔隙水压力对其稳定性的影响,并以反演获得的强度参数结合类似边坡岩体结构面强度试验统计结果,对原边坡进行了可靠度分析,获得了原边坡的潜在破坏概率,从而又在定量角度上获得了滑坡发生的原因。

Mechanism Analysis of Landslide of a Layered Slope Induced by Drawdown of Water Level

The frequent drawdown of water level of Yangtze River will greatly influence the stability of the widely existing slopes in the Three Gorges reservoir zone, especially those layered ones. Apart from the fluctuating speed of water level, the different geological materials will also play important roles in the failure of slopes. Thus, it must be first to study the mechanism of such a landslide caused by drawdown of water level.A new experimental setup is designed to study the performance of a layered slope under the drawdown of water level. The pattern of landslide of a layered slope induced by drawdown of water level has been explored by means of simulating experiments. The influence of fluctuating speed of water level on the stability of the layered slope is probed,especially the whole process of deformation and development of landslide of the slope versus time. The experimental results show that the slope is stable during the water level rising, and the sliding body occurs in the upper layer of the slope under a certain drawdown speed of water level. In the process of slope failure, some new small sliding body will develop on the main sliding body, and the result is that they speed up the disassembly of the whole slope.Based on the simulating experiment on landslide of a layered slope induced by drawdown of water level, the stress and displacement field of the slope are calculated.The seepage velocity, the pore water pressure, and the gradient of pore water head are also calculated for the whole process of drawdown of water level. The computing results are in good agreement with the experimental results. Accordingly, the mechanism of deformation and landslide of the layered slope induced by drawdown of water level is analyzed. It may provide basis for treating this kind of layered slopes in practical engineering.

Application of Three-Dimensional Discrete Element Face-to-Face Contact Model with Fissure Water Pressure to Stability Analysis of Landslide in Panluo Iron Mine

Three-dimensional discrete element face-to-face contact model with fissure water pressure is established in this paper and the model is used to simulate three-stage process of landslide under fissure water pressure in the opencast mine, according to the actual state of landslide in Panluo iron mine where landslide happened in 1990 and was fathered in 1999. The calculation results show that fissure water pressure on the sliding surface is the main reason causing landslide and the local soft interlayer weakens the stability of slope. If the discrete element method adopts the same assumption as the limit equilibrium method, the results of two methods are in good agreement; while if the assumption is not adopted in the discrete element method, the critical phi numerically calculated is less than the one calculated by use of the limit equilibrium method for the same C. Thus, from an engineering point of view, the result from the discrete element model simulation is safer and has more widely application since the discrete element model takes into account the effect of rock mass structures.

Effects of Fracture Seepage on the Stability of Landslide during Reservoir Water Level Fluctuation

The hydraulic conductivity function of fractures is a key scientific question to describe and reveal the process and the role of water seepage reasonably. In this paper, the generation technology of random fracture network and the latest numerical computation method for equivalent permeability tensor of fracture network are applied to analyze the landslide located at Wangjiayuanzi in Wanzhou District of Chongqing by simulating the changes of the seepage field caused by the running of the Three Gorges Reservoir. The influences of the fracture seepage on the seepage field and stability of the landslide were discussed with emphasis. The results show that the fractures existing in the soil increase the permeability coefficient of the landslide body and reduce the delay time of the underground water level in the landslide which fluctuates relative to the water level of reservoir，that causes the safe coefficient of the slope changes more gently than that of the same slope without fractures. It means, if only water level fluctuating condition is concerned, the fractures existing in the soil plays a positive role to the stability of slopes.

潘洛铁矿滑坡特征分析及防治

分析了潘洛铁矿露天矿滑坡灾害发生发展的特征,得出该滑坡是一个动态的、多层次的复合型滑坡;找出了影响该边坡稳定的主要因素是大气降雨和采矿切割坡脚;根据这些影响因素和滑坡发展变化规律,提出了科学合理的滑坡治理方案,即动态的综合治理方案.经现场实施后,通过滑坡监测数据表明,该滑坡得到了彻底根治.

高速滑坡中的热效应分析

从理论和数值分析两方面讨论滑坡滑带内热致孔隙压力及其对高速滑坡的影响.首先给出土体动力平衡方程、热和孔压的产生与耗散方程构成的热-水压-力学模型,然后在该模型基础上讨论滑带(局部化剪切带)产生的条件,对滑带宽度的演化及影响因素进行分析,最后探讨土体变形产生热而导致高孔隙压力及低摩擦系数的问题.结果表明,当热软化效应超过应变硬化效应后,失稳就将发生.失稳后,土体发生剪切局部化变形,在滑坡的滑面内产生剧烈变形.一般情况下,滑带宽度是变化的,其变化对滑带内应变、应变率有很大的影响,从而导致滑带内孔隙压力、温度等的明显变化.滑坡的加速运动是由于剪切带中材料的变形,热被集中于剪切带内,而导致其中孔隙压力的快速上升和土体强度的快速下降引起的.

库水浸泡后滑坡体中水分布的实验研究

建立了室内模拟库水浸泡后滑坡体内水润湿的渗流实验装置,根据清江茅坪滑坡的地形、地貌以及岩土混合比例,填制了岩土体实验模型.模拟了水位在涨至模拟坡体凌空面一半高度和水位漫过凌空面达到第一平台高度时,坡体内的水分布情况.在水位降落实验过程中,岩土体部分失稳,证明了润湿滞后在降水期滑坡中起主要作用.

清江水库茅坪滑坡监测与发展趋势预测

茅坪滑坡位于清江隔河岩水库上游北岸、距水库坝址66km处。是隔河岩水库库区中最大的基岩古滑坡体，其体积约2．35×10^7m^3。自1993年4月10日水库下闸蓄水以来，该滑坡一直产生缓慢变形。滑坡发生整体失稳，则会截断清江，形成“库中坝”，并造成灾难性的恶果。为此，全面掌握该滑坡的变化发展趋势对今后进行防治决策具有十分重要的意义。掌握滑坡发展变化的关键就是对该滑坡进行现场监测。课题组多次现场踏勘，在原有8个地表监测点的基础上增设了29个监测点，使其布置更科学、合理；并对该滑坡进行了1个水文年的监测工作，获得了大量的笫一手资料，认为该滑坡正处于位移加速阶段。通过现场监测，不仅对滑坡体的现状有了新的认识。同时，预测了茅坪滑坡的变化发展趋势，可以为制定该滑坡的防治预案提供参考。

An Extension of 2D Janbu’s Generalized Procedure of Slices for 3D Slope Stability Analysis II—Numerical Method and Applications

This paper provides a numerical approach on achieving the limit equilibrium method for 3D slope stability analysis proposed in the theoretical part of the previous paper. Some programming techniques are presented to ensure the maneuverability of the method. Three examples are introduced to illustrate the use of this method. The results are given in detail such as the local factor of safety and local potential sliding direction for a slope. As the method is an extension of 2D Janbu's generalized procedure of slices (GPS), the results obtained by GPS for the longitudinal sections of a slope are also given for comparison with the 3D results. A practical landslide in Yunyang, the Three Gorges, of China, is also analyzed by the present method. Moreover, the proposed method has the advantages and disadvantages of GPS. The problem frequently encountered in calculation process is still about the convergency, especially in analyzing the stability of a cutting corner. Some advice on discretization is given to ensure convergence when the present method is used. However, the problem about convergency still needs to be further explored based on the rigorous theoretical background.

抗滑桩阻力上下限解法

基于工程上常用的Janbu普遍条分法(GPS)和剩余推力法，提出了确定单排或多排抗滑桩抗滑阻力的上、下限计算方法。该法假定桩前、桩后滑动土体具有不同的稳定性系数，或假定桩前、桩后滑动土体具有不同的剩余推力，并且抗滑桩承受的下滑力是水平距离的函数。对于单排桩，借助于下限法可以通过试算确定其设桩范围；对于多排桩，借助于上限法可以通过有限的组合枚举确定其最佳的配置。上、下限法的结合可以巨大降低计算量，同时又能满足工程精度要求。运用该方法还可以确定不宜设置抗滑桩的位置范围。文中的算例展示了该方法的具体运用过程。