不排水条件下土石混合料双轴压缩离散元模拟

Discrete element simulation of soil-rock mixture under biaxial compression under undrained condition

基于离散单元法构建了考虑碎石形状的柔性边界不排水双轴压缩模型,研究了11组不同含石量土石混合料在不排水条件下的宏细观力学特性。研究发现,(1)土石混合料强度随含石量增加先增后减,含石量超过约60%时形成碎石骨架,强度快速增长;含石量约80%时强度和内摩擦角最大;含石量增加,混合料黏聚力逐渐减小。(2)不排水受载下,土石混合料孔隙水压力先正后负、先增后减。含石量较小时,含石量增加,混合料孔隙水压力变化较小,混合料在碎石骨架形成初期孔隙水压力增加;碎石骨架完全形成后最大孔隙水压力减小。(3)含石量小于约30%时,混合料应变局部化呈规则剪切带,随后含石量增加破坏规则剪切带,当含石量约为80%时,混合料再次形成规则剪切带。含石量增加,配位数逐渐减小,颗粒间接触力在含石量小于60%时随含石量增加缓慢增长,超过70%时则快速增长。

An undrained biaxial compression model with a flexible boundary considering the shape of macadam is constructed by the discrete element method.The macro-meso mechanical properties of 11 groups of soil-rock mixtures with different stone contents under undrained conditions were studied.It is found that:(1)The strength of the soil-rock mixture increases at first and then decreases with the increase of stone contents.The strength of the crushed stone skeleton formed by the mixture containing more than 60%stone increases rapidly.The maximum strength and internal friction angle are obtained when the stone content is about 80%.The cohesion of the mixture decreases with the increase of stone contents.(2)Under undrained loading,the pore water pressure of the soil-rock mixture is first positive and then negative first increases and then decreases.When the stone contents are small,the change of pore water pressure of macadam mixture is small.The pore water pressure of the mixture increases at the initial stage of the formation of the crushed stone skeleton,and the maximum pore water pressure of the macadam skeleton decreases.(3)The strain localization of soil-rock mixture with stone contents less than 30%is a regular shear zone.The stone contents increases to destroy regular shear,and when the stone contents are about 80%,the mixture forms a regular shear zone.With the increase of stone contents,the coordination number decreases gradually,and the indirect contact force of particles increases slowly with the increase of stone contents when the stone contents are less than 60%,and increases rapidly when it exceeds 70%.