点载荷作用下密集颗粒物质的传力特性分析

THE QUASISTATIC RESPONSE OF A GRANULAR MATTER TO A LOCALIZED LOADING

利用颗粒离散元商业软件PFC3D,模拟了在2m×1m×0.01m容器中直径分别为0.01 m,0.008 m和0.006 m的颗粒各1×10~4个,受重力作用下的静态密集堆积;以此为初始条件,在表层随机选择7个颗粒分别施加5.2×10^(-2) N(100倍最大颗粒重量)的点载荷,进行应力传播特点研究.结果表明:力的传递在局部范围内呈现很强的各向异性;应力涨落随着距离的增加呈指数下降;在大于5倍最大颗粒粒径时,其分布可以使用弹性力学理论来计算.探讨了摩擦系数μ=0,0.2,1对应力传递的影响,随着摩擦系数的增加,各向异性范围减小.

A localized small force provides a unique non invasive probe based on both the structure of the force chain network and the response of granular matter.In this work,quasistatic packings of 30000 spherical particles confined within a 2m×1m×0.01m container are simulated by using discrete element method.The sizes of particles are 0.01 m,0.008 m and 0.006 m,respectively,and the number of particles of each size is 10 000. A localized force is exerted on one of the top layer particles with a small magnitude of 5.2×10^（-2）N,which is 100 times of the weight of the largest particle with the size of 0.01 m in order to ensure that the granular material keeps still.The results show strong heterogeneous pathways of force propagation and the fluctuations of force are evident.With the increase of the distance from the exerted particle,the force fluctuations are reduced.The calculated stress values agree with the Flamant solutions of stress as the distance is more than 5 times the size of the largest particle.The effect of surface friction of particles is discussed.The preliminary results indicate that a larger friction coefficient leads to more uniform stress distributions.