基于离散元法的贯入圆锥对沙土颗粒运动特性分析

为了预测土壤颗粒在圆锥指数仪贯入沙土过程中的运动特性,该文通过建立一个三维长方体料床模型用离散元法模拟了圆锥贯入沙土的全过程,讨论了料床指定初始位置上颗粒的运动轨迹,还将料床的位移场按照位移量大小分成4个区,分析了料床的横向、纵向以及合成的位移场,最后给出了不同贯入深度的料床速度场及力链分布规律。研究结果显示:受到圆锥向下贯入和左右壁面阻挡的共同作用,大多数颗粒在圆锥贯入过程中以纵向移动为主,横向上体现为近似线性梯度的受限扩散式移动,尤以锥尖附近的横向位移最明显;颗粒在纵向上均经历了先向下运动再向上运动的过程,在圆锥贯入过程中料床的纵向位移场,作为向上和向下位移区的分界线,一条"衣领"带状区域的颗粒近似静止;越靠近锥尖附近的颗粒接触力和速度越大,且随着贯入深度的增加,锥尖处的接触力增大。该文的研究为土壤圆锥指数实地测量时测量点间距的取值提供理论依据。

Influence of penetrating cone on motion characteristics of sandy soil particle using discrete element method

In order to predict the motion characteristics of soil particles during the penetration of the cone, simulations of cone penetration into sandy soil with DEM were carried out by establishing a 3D cuboid granular bed. In this study, it was mainly discussed about the trajectories of the given particles, the horizontal, vertical and resultant displacement fields, the velocity fields and contact-force fields of the granular bed. The results showed that vertical motion was dominated for the most particles, while the horizontal behave was the limited diffusion in approximately linear gradient and the lateral displacement of particles near the cone tip was obvious. In addition, most particles exhibited upward motion first and then downward motion, and a collar-shape zone became the boundary dividing the displacement zone upward and downward during the penetration, and the particles within the collar-shape zone were almost static. Finally, the contact forces and velocities of the particles closed to the cone tip were much larger, and the contact force became larger as the increasing of penetration depth. This study may provide a reference for the determination of distance between sampling points in the in-situ measurement of Cone Index.