准静态侵入颗粒介质的底边界效应仿真分析

Numerical Study on Bottom Boundary Effect in Quasi-Static Intrusion into Granular Media

论文基于球形离散元方法研究颗粒介质的底边界效应,仿真刚体圆柱准静态侵入有限厚度颗粒介质直至底边界的过程,探究侵入物所受阻力与侵入深度间关系.结果表明,圆柱准静态侵入颗粒层至池底的阻力-深度曲线,前段呈类静水压力线性,接近底边界的后段呈类指数增长形式;在距底数个粒径范围内阻力存在波动,波长近似颗粒直径.与圆柱底固连的倒锥形固化区颗粒存在动态更新,侵入接近底边界时固化区瓦解,局部颗粒阻塞与疏通决定阻力增长趋势;圆柱底面以下的颗粒力链在接近底边界时转化为圆柱底与颗粒池底之间的“底-底”力链,力链受挤压后平均颗粒数的递减很好地解释了阻力振荡的波动性.

Based on the spherical discrete element method,this paper studies the bottom boundary effect of granular media,simulates the quasi-static intrusion of rigid body cylinders into particle media with limited thickness to the bottom boundary,and explores the relationship between the resistance of intruder and the depth of intrusion.The results show that the resistance-depth curve of the cylindrical quasi-static intrusion particle layer to the bottom of the pool has a linear hydrostatic pressure in the front section and an exponential growth form in the back section near the bottom boundary.However,there are fluctuations in resistance within a few particle sizes from the bottom,and the wavelength is approximately the same length as the particle diameter.Furthermore,the particles in the inverted conical curing zone connected to the cylindrical bottom have dynamic renewal.The curing zone collapses when the intrusion is close to the bottom boundary,where the local particle blocking determines the resistance growth trend.Additionally,the particle force chain below the bottom of the cylinder is transformed into a“bottom-bottom”force chain between the bottom of the cylinder and the bottom of the particle pool when it approaches the bottom boundary.The decrease in the average number of particles after the force chain is squeezed explains the volatility of the resistance oscillation.