观音岩滑坡潜在失稳模式及成灾规模数值模拟

Analysis on Potential Failure Mode and Disaster Range of Guanyinyan Landslide

基于颗粒接触的无网格方法(PCMM)以颗粒离散元的几何构型为依托,将研究区域用一系列颗粒进行离散,而后基于颗粒间复杂丰富的接触信息构建三角形单元,并在单元中引入Mohr-Coulomb理想弹塑性本构模型。计算过程中,随着颗粒间接触信息的变化,一些畸变单元将会被自动删除,一些新单元将会被自动创建。通过单元的删除及重建,即可解决滑坡数值模拟中因网格畸变导致的系统能量发散问题。利用PCMM方法结合强度折减思路,对重庆黔江观音岩滑坡的潜在失稳模式及成灾规模进行了探讨。计算结果表明,观音岩滑坡为典型的土质推移式滑坡,滑体后部先出现失稳破坏,并出现局部张拉裂缝;剩余下滑力的转移导致滑体前部出现剪切破坏;最后滑体中部出现破坏;滑移面形成的顺序为后部、前部、中部。观音岩滑坡失稳后,滑体涌入黔江河道的方量与强度折减系数呈线性关系,随着强度折减系数的增加,滑体涌入量线性增加。强度折减系数为1.3时,滑体涌入量约为3万方;强度折减系数为2.0时,滑体涌入量约为25万方。

Particle contact-based meshfree method （PCMM） is based on geometric configuration of particle DEM. In PCMM, the study area is discretized by series of particles, then triangle elements are created based on the complicated and abundant contact information, and finally Mohr-Coulomb ideal elastic-plastic constitutive model is introduced to each element. During ,calculation, according to the variation of contact topology between particles, some distorted elements will be.. deleted, and some new elements will be created automatically. According to the element deletion and reconstruction, the convergence problem due to grid distortion in simulating landslide could be solved. Based on PCMM and strength reduction approach, the potential failure mode and disaster range of Chongqing Qianjiang Guanyinyan landslide is discussed. Numerical results show that, Guanyinyan landslide is a typical push-type soil landslide. The failure appears on the backside firstly, with some tensile fractures; then the shear failure occurs on the foreside of landslide due to the transfer of residual sliding force ; at last, the failure occurs in the middle. The formation sequence of sliding surface is backside, foreside and middle. If the Guanyinyan landslide begins to slide, there is a good linear relationship between the soil volume sliding into the river and strength reduction factor. With the increase of strength reduction factor, the volume increases linearly. When the strength reduction factor is 1.3, the volume is 30,000 m^3; while the strength reduction factor is 2.0, the volume is 250,000 m^3.