非饱和粗、细颗粒混合土在动荷载作用下的细观力学响应

为了研究非饱和粗、细颗粒混合土在动荷载作用下的细观力学性质,进行了非饱和粗、细颗粒混合土动三轴的离散元数值分析。根据室内动三轴试验结果标定PFC2D接触模型参数,进行非饱和粗、细颗粒混合土动三轴离散元模拟,分析其细观力学机理。结果表明:离散元模拟结果与室内试验结果曲线拟合度基本一致,能较好地反映非饱和粗、细颗粒混合土在动荷载作用下力学特征。相同含水率条件下,粗、细颗粒混合土的累积动应变随动应力幅值的增加而增大;随围压的增加先小幅度增大后再大幅度减小。孔隙度随动应力幅值的增大而减小;随围压的增大也减小。试样颗粒在剪切过程中,上下端运动速度最大,整体呈现对称递减状,中部运动速度最小。

Meso-mechanical Response of Unsaturated coarse and Fine-grained Mixed Soil under Dynamic Load

In order to study the meso-mechanical properties of unsaturated coarse-grained soil under dynamic load, the dynamic triaxial discrete element numerical analysis of unsaturated coarse-grained soil is carried out. According to the indoor dynamic triaxial test results, the PFC2D contact model parameters are calibrated. the dynamic triaxial discrete element simulation of unsaturated coarse-grained soil is carried out to analyze its meso-mechanical mechanism. The results show that the discrete element simulation results can better reflect the mechanical characteristics of unsaturated coarse-grained soils under dynamic loads. Under the same confining pressure, the normal and tangential contact forces in all directions of the unsaturated coarse-grained soil sample increase with the increase of the dynamic stress amplitude. Under the condition of the same water content, the cumulative dynamic strain of coarse-grained soil increases with the increase of the dynamic stress amplitude; with the increase of confining pressure, it first increases slightly and then decreases greatly. The porosity decreases with the increase of dynamic stress amplitude; it also decreases with the increase of confining pressure. During the shearing process of the specimen, the upper and lower ends move at the highest speed, the whole is symmetrically decreasing, and the middle section moves at the smallest speed.