基于黏结颗粒模型某滑坡土石混合体直剪试验数值模拟

摘要

The elementary process of establishing numerical model based on digital image processing is introduced. According to the method,the particle flow numerical models of soil and rock mixture(SRM) can be obtained directly by field digital photos. Taking SRM in a landslide near the dam of Xiluodu hydropower station for example,the numerical model is established by field photo. The micro-mechanical parameters of gravel and soil are well studied by using the particle flow code in two dimensions(PFC2D);and micro-mechanical parameters corresponding to their macro-mechanical features are selected. The numerical simulation of direct shear test for the SRM is conducted under serious normal pressures and the results of SRM are compared with those of heterogeneous soil. The main research results can be summarized as follows:Firstly,the microparameters of soil inversely calculated by biaxial compression test is used in direct shear test to get macroparameters of soil;and these macroparameters are consistent with practice. Compared with heterogeneous soil,the initial shear stiffness of the SRM with certain content gravel is higher,and the shear displacement required for the SRM reaching to its peak shear strength is reduced. Under the assumption that the bonded strength between gravel and soil is one tenth of the soils,the internal friction angle of the SRM is larger,while the cohesion is lower. Compared with the fracture plane in heterogeneous soil model after direct shear tests,the cracks developed in the SRM numerical model can be divided into two parts:some are around the shear plane formed broad fractures band,the others distribute between gravel and soil. Also according to the characters of shear failure,the reason for enhancing shear performance of the SRM which contains a certain amount of gravel can be introduced qualitatively.%　　介绍基于数字图像处理建立数值模型的基本过程，实现由现场数字照片直接生成土石混合体的颗粒流模型。以溪洛渡水电站坝址附近某滑坡土石混合体为例，基于实拍照片建立其细观数值模型，利用 PFC2D程序分析碎石和土体数值模型中微观力学参数的反算问题，分别为滑坡体中的碎石和土体选定与其宏观力学特征相一致的微观力学参数，进行直剪试验的数值模拟，并与均质土体的模拟结果相比较。结果显示：利用双轴试验反算的土体微观参数运用于直剪试验获得的宏观力学参数与实际一致；一定含量的碎石使土石混合体的初始剪切刚度较均质土有所增大，达到峰值抗剪强度所需的剪切位移减少；假定土石界面的黏结强度为土体内部的1/10时，土石混合体的内摩擦角明显增大，而黏聚力则稍有减少；与均质土体直剪形成的破裂面相比，土石混合体模型中的裂隙部分集中于剪切面呈宽带状，部分存在碎石与土体分界面，基于此可定性探讨一定碎石含量的土石混合体抗剪性能优于均质土体的原因。