基于PFC2D的砂土原生各向异性微观机理数值试验

Numerical experiments of microscopic mechanism of inherent anisotropy for sand based on PFC2D

采用颗粒流PFC数值模拟方法,生成符合标准砂室内单元试验结果的离散元数值试验试样。运用重力沉积法建立不规则砂土颗粒单元的平面双轴试验模型,给定不同沉积步数对试样不同初始原生状态进行模拟,然后分别从水平和竖直方向上施加荷载增量,得到不同沉积条件下不同加载方向上砂土试样宏观应力应变曲线和力学参数。数值试验结果显示,重力沉积步数对颗粒微观长轴定向排列、平均配位数有显著影响;初步建立了砂土微观结构变化和宏观应力应变曲线及力学参数的联系;分析了砂土试样表现出的宏观原生各向异性力学特性与内部颗粒结构的关系。

Through numerical simulation based on the particle flow method, DEM numerical test samples are generated in accordance with the results of laboratory tests on standard sand. Using gravity deposition modelling of irregular sand particles, samples of biaxial test assembled by long particle units are generated. Different steps of deposition are applied during the process of generating samples in order to simulate different inherent states of samples. The loads from the horizontal and vertical directions are respectively applied to samples. The numerical experimental results show that the gravitational deposits have significant impact on the major axis orientation arrangement of particles and the average coordination number. Also, there is a change in the macroscopic stress-strain curve and mechanical parameters acquired from the results of applying loads to the samples from the horizontal and vertical directions. The tested sand samples exhibit inherent mechanical anisotropy, which is closely associated with the internal structure properties and microscopic mechanical properties of sand.