含抗转能力散粒体的宏微观力学特性数值分析

Numerical investigation on macro-micro mechanical behavours of granular materials incorporating rolling resistance

颗粒间抗转因素对散粒体宏微观特性的影响十分显著。本文采用离散单元法,将蒋明镜(2005年)等提出的抗转动接触模型植入离散元分析软件PFC2D中,模拟了大量刚性边界下的砂土双轴试验,研究了压缩过程中试样的宏观力学性质及部分微观参量的变化情况,用以定性分析颗粒间抗转作用对散粒体的宏微观力学特性的影响。研究表明:颗粒间的抗转作用对散粒体的宏微观特性影响显著。宏观上,抗转系数越大,试样的强度及剪胀越明显,抗转系数达到一定值时松砂试样亦会出现软化及剪胀现象,内摩擦角随抗转系数的增加而增大;微观上,同一围压下,抗转系数越大,砂土颗粒平均接触数即配位数稳定值越小,接触点方向性越明显。

Rolling resistance is very important to control the macro-micro mechanical behaviour of granular materials.This paper studies the effects of rolling resistance on the behaviour of granular materials using PFC2D.A novel contact model incorporating rolling resistance proposed by Jiang etc.（2005） is implemented into PFC2D firstly.Based on the biaxial compression tests on this material,the effects of rolling resistance on the behavior of sand are then studied.Some microscopic indexes including the average coordination number and contact fabric are studied too.The results show that the rolling resistance is very important in controlling the peak strength and leading to extensive dilatancy of sand.In the case that the rolling resistance is larger than a specific value,loose sand specimen can also demonstrate strain-softening and shear-dilantant behavior.With the increasing of rolling resistance,both the internal friction angle and the peak（residual） strength of specimen increase,while the average coordination number of the specimen reduces.The coordination number always tends to approach a constant value which decreases with the increasing of rolling resistance.