【作者】 袁灿；

【导师】 欧湘萍；

【作者基本信息】 武汉理工大学 ， 道路与铁道工程， 2008， 硕士

【摘要】 边坡稳定分析的方法很多,传统上主要采用极限平衡分析方法。近年来,引入了强度折减法,强度折减法是结合有限元或有限差分等数值计算方法来实现边坡稳定性分析的。采用有限差分强度折减法进行边坡稳定分析,能直接得到安全系数和最危险滑动面,并且能得到边坡的应力场分布,还可以描述边坡的失稳过程。以浅变质岩风化层边坡为研究对象,基于FLAG-3D软件,结合有限差分强度折减理论,对浅变质岩风化层边坡进行了稳定性分析。分析研究了浅变质岩风化层边坡的工程特性;对现有的边坡失稳判据进行了分析对比,选定计算收敛判据作为失稳判据,并利用FLAG-3D软件编译相应的程序来实现强度折减法,求解边坡安全系数并搜索最危险滑动面;选取了一个均质边坡和一个非均质边坡作为算例,运用自编强度折减法程序进行边坡稳定分析,验证了本文算法的适用性;基于均质边坡算例,简单分析了计算网格划分和内摩擦角、粘聚力、弹性模量、泊松比等参数对边坡安全系数计算值的影响;运用本文分析方法对某浅变质岩风化层边坡稳定性进行了分析。得出以下主要结论:(1)浅变质岩风化层边坡岩体的物理力学性质差,强度低,坡体内构造面、小断层发育,风化后形成软弱带,导致浅变质岩风化层边坡自身稳定性差。在降雨、坡体开挖等因素的影响下,浅变质岩风化层边坡极易发生边坡失稳。(2)建立计算模型时要合理的划分计算网格。当网格划分密度较低时,边坡的安全系数随网格密度的增加而减小,且变化较大;当网格划分密度较高后,边坡的安全系数随网格密度的增加而引起的变化较小。网格密度过低会影响计算精度,而过高的网格密度则会消耗过多的计算时间,因此一般要通过试算来确定合理的网格密度。(3)在相同的计算条件下,内摩擦角φ对安全系数计算值的影响较大,粘聚力c次之,弹性模量E和泊松比μ对边坡的安全系数计算值几乎没有影响。(4)本文基于FLAG-3D软件的自编强度折减法计算程序具有一定的适用性,可以较为准确地确定边坡的安全系数和最危险滑动面的位置。更多还原

【Abstract】 There are many methods for the slope stability analysis, the limiting equilibrium method is mainly used traditionally, the strength reduction method which analyses slope stability with finite element or finite difference method is introduced these years. According to the strength reduction method with finite difference , the factor of safety and the most dangerous slip surface can be obtained directly, the stress field and the process of destabilization can be shown too.This paper takes the slightly weathered rock as subject investigated, and uses the strength reduction method with finite difference based on FLAC-3D software to analyse the stability of slightly weathered rock slope.This paper researches the engineering characteristic of the slightly weathered rock slope, analyses the existing criterions of destabilization and takes the convergence criterion. This paper makes a program based on FLAC-3D software to carry out the strength reduction method, and gets the factor of safety and the most dangerous slip surface according to it. This paper takes one homogeneous slope and one heterogeneous slope as examples to test the self-orgnizing strength reduction method which is mentioned above. Based on the homogeneous slope, it simply analyses the influence to the factor of safety of the mesh, internal friction angle, cohesive strength, Young’s modulus and Poisson’s ratio. Finally it analyses an instance of the slightly weathered rock slope by the self-orgnizing strength reduction method. The conclusions are as follows:(1) Because of bad physical mechanical property of rock mass, low strength, so many structural planes and minor faults which leads to weak strip after weathered, the homeostasis of the slightly weathered rock slope is serious. With the influence of external factors such as rainfall, engineering projects and unreasonable job practicees, it’s very easy to be unstable.(2) The mesh should be ploted reasonably in the process of model building. When the mesh density is low, the factor of safety reduces greatly with the increase of mesh density, when the mesh density is high, the factor of safety changes little with the increase of mesh density. The precision of calculation will not be nice if the mesh density is too low, contrarily it will cost too much time to calculate if the mesh density is too high. So it’s normally need to confirm the reasonable mesh density according to pilot calculation.(3) With the same computational condition, internal friction angle influences the calculation of factor of safety greately, cohesive strength takes second place, Young’s modulus and Poisson’s ratio influences the calculation of factor of safety hardly.(4) The self-orgnizing strength reduction method based on FLAC-3D software in this paper is applicable, it can get reasonable factor of safety and the most dangerous slip surface.更多还原