双滑移转动率模型对椭圆散粒体的适用性

Applicability of double slip and rotation rate model for elliptical granular assemblage

首先基于椭圆颗粒接触点的运动关系推导出新的平均纯转动率(APR)表达式,并将其引入到已有的描述圆形散粒体流动特性的双滑移转动率模型(DSR2模型)中;而后采用改进的NS2D离散元程序对长短轴比例分别为1.4和1.7的椭圆颗粒堆积体进行一系列不排水单剪试验,验证以椭圆颗粒为基础的离散元方法模拟砂土流动特性的可行性及DSR2模型的合理性。数值试验及已有成果表明,以椭圆颗粒为基础的NS2D程序能够模拟砂土的流动特性,对圆形和椭圆形颗粒体系,DSR2模型均能很好地预测运动模型中转动率参量的变化情况;APR是联系连续介质力学和离散介质力学的重要参数,它将二者有机结合成一个整体。

The averaged micro-pure rotation rate （APR） based on the relative movement of contact between two ellipses has been derived first.The APR was then introduced into the double slip and rotation rate model （DSR2 model） which was proposed originally for plastic flow of circular granular assemblages.A developed distinct element method （DEM） program NS2D was utilized to generate two-dimensional assemblages of elliptical particles with individual aspect ratio of 1.4 and 1.7.Then a series of undrained monotonic and cyclic simple shear tests on these assemblages were conducted to reproduce the plastic flow of elliptical particles and to validate the DSR2 model.The results show that the developed NS2D program which is based on elliptical particles can reproduce the plastic flow behaviors of sand.The DSR2 model appears to be able to predict the variation of angular velocity in kinematic models of both circular and elliptical particle assemblages.This indicates that the APR is an important variable which bridges discrete and continuum granular mechanics.