土石混合体原位试验的颗粒流数值模拟分析

Particle Flow Modeling of Soil-Rock Mixtures In-situ Tests

基于颗粒流理论和PFC程序,解决了不规则碎石(clump)的生成、恒定法向荷载施加、剪切面的含石量等问题后,建立了土石混合体原位试验的颗粒流数值模型,对不同含石量、法向应力下土石混合体的直剪试验进行模拟,并与原位直剪试验的结果进行比较.结果表明:随着含石量增加,剪切应力及其峰值增大,剪切应力峰值对应的剪切位移减小;在低法向应力条件下,土石混合体表现为剪胀;在高法向应力下,土石混合体表现为先剪缩而后剪胀,并呈现出压剪破坏特征;剪切面附近分布的不规则碎石在剪切过程中出现挤压滑动与滚动,使得剪切破坏面出现凹凸,而且剪应力、法向位移、应变能随剪切位移增加而出现波动和平缓段;数值试验所得剪切应力峰值略高于其试验值,减小模型颗粒半径,可以有效降低计算的剪切应力峰值.

The numerical simulation of soil-rock mixtures（S/RM） shear test was successfully performed using the particle flow theory based on particle flow code （PFC）, by creating irregular clumps, constant normal stress and rock content in shearing surface. Based on the clump of PFC with different stone con- tent, different normal stress of S/RM direct shear test simulation were elaborately discussed. The reliabili- ty of the simulation method was verified by comparing calculation results and in-situ shear test. The main research results indicate that with the increase of rock content, the shear stress and the peak shear stress increase, while the shear displacement at the peak shear stress decreases. S/RM samples exhibit shear dil- atation characteristics at low normal stress and tend to transform from shear contraction to dilatation at higher stress, with pressure shear failure characteristics. In the near shear plane distributing the irregular rock clump, the shear appeares in the process of extrusion sliding and rolling shear failure surface grows concave and convex. With shear displacement increasing, the shear stress and strain energy fluctuate and grow gentle. The peak shear stress obtained from the numerical calculation is higher than that of the in-situ test. The calculated peak shear stress can be decreased effectively by reducing the particle radius.