安全与环境工程

黏性土的直剪离散元模拟试验中,土体的宏观力学行为、内部颗粒运动和颗粒间接触力的变化特征与模型的细观参数密切相关。采用线性接触黏结模型和滚动阻力接触模型对黏性土的剪切过程进行模拟,分析剪切带内外的差异,采用正交试验分析细观参数变化对于模拟试样的宏观剪应力、黏结破坏数量、平均配位数和力链组构参数的影响。结果表明:颗粒有效模量越大,试样剪切过程中颗粒间黏结破坏数量越多,接触力分布越不均匀,宏观剪应力越大;颗粒刚度比对试样剪切过程中变形的影响较小;颗粒间切向黏结力的影响比法向黏结力大,颗粒间法向黏结力和切向黏结力越大时,弱力链体系颗粒间接触力的分布越均匀,试样剪切过程中宏观剪应力越大;摩擦系数在颗粒间黏结破坏后起作用,摩擦系数越大,模型中颗粒间黏结破坏数量越多,试样剪切过程中宏观剪应力越大,但对试样剪切带内颗粒间接触力分布的影响不大;滚动摩擦系数在颗粒产生滚动后起作用,滚动摩擦系数越大,试样内颗粒间接触力的分布越不均匀,试样剪切过程中宏观剪应力越大。

The macroscopic mechanical behavior and soil particle motions and the variation on contact force are related to mesoscopic parameters of specimens in the direct shear discrete element simulation test of cohesive soil.This paper simulates the shearing process of cohesive soil by the linear contact bond model and the rolling resistance linear model, analyzes the differences between inside and outside the shear band, and the effects of mesoscopic parameters on macroscopic shear stress, bond failure number, average coordination number, and fabric parameters of force chains of specimens by the orthogonal test.The results are as follows: during the shear process of specimens, when the effective modulus of the particles is larger, there will be more bond failure between particles and the distribution of contact force will be more inhomogeneous and the macro shear stress will be larger; the influence of particle stiffness ratio on deformation during the shear process of specimens is small; the influence of the tangential bond force is greater than the normal bond force, and when the normal bond force and the tangential bond force increase, the distribution of contact among particles in the weak force chain will be more homogeneous and the macro shear stress will be larger during the shear process of specimens; the friction coefficient takes effect when the bond among particles is broken, and when the friction coefficient increases there will be more bond failure and the macro shear stress will be larger, while the distribution of contact force among particles in the specimen shear band change little; the rolling friction coefficient takes effect when particles roll, and when the rolling friction coefficient increases, there will be more bond failure and the distribution of contact force between particles in the specimens will be more inhomogeneous and the macro shear stress will be larger.