降雨作用下崩岗形成细观机理模拟

Meso-mechanical Simulation of Slope Disintegration Erosion Under Rainfall

崩岗是我国南方地区一种特殊水土流失现象。利用颗粒流PFC3D软件,结合流体力学数值模拟有限体积法,通过三轴实验与数值试验结果对比,获得与宏观参数相匹配的细观参数,建立崩岗坡体模型。通过模拟不同降雨强度,再现崩岗坡体渐进性破坏过程。崩岗的形成历经裂隙发生、发展直至崩滑面贯通,最后崩岗产生。在高强度降雨条件下崩岗具有分块、分级特点。与此同时,对崩岗形成过程中岩土体渗透系数、孔隙水压力与坡面渗流量等变化发展规律也进行了研究。渗透系数总趋势随着时间的推移先增大,到达峰值后减小;而渗流量却表现为增加,当降雨强度大时,还表现为跳跃式增长。孔隙水压力在低降雨强度下,增长后随后稳定;在高降雨强度下,波动较大。研究结果与实际较为吻合,表明采用颗粒流研究崩岗的形成机理是可行的。

Slope disintegration is a special type of water and soil loss phenomenon in the south of China. Based on particle flow theory and finite volume method of fluid dynamics, the Meso-mechanieal parameters obtained by com- paring the PFC3~ and that of triaxiaI test results, a numerical model of slope disintegration is set up. The gradual forming process of slope disintegration is simulated under different rain intensity. The results show the failure under- goes a process of fissure formed and developed until slope disintegration occurs. Under high rain intensity, it has the features of blocks and multi-grades. Meanwhile, the development of the permeability, pore pressure and seep- age discharge in the slope are also discussed. Permeability increases with time passing until it arrives its maximum, then decreases; While the seepage discharge keeps increasing, especially sharply under heavy rain; The pore pres- sure under low rain intensity firstly increases, then is steady, hut fluctuates under high rain intensity. The results of the research is similar to the site conditions, which proves the feasibility of particle flow theory in the study of mechanism of slope disintegration .