黏性土失水开裂多场耦合离散元数值模拟

NUMERICAL SIMULATION OF DRYING CRACKING USING MULTI-FIELD COUPLING DISCRETE ELEMENT METHOD

黏性土在失水过程中逐渐变形开裂,裂隙相互交错形成网络,这一过程涉及水热力等多场耦合的作用。本文基于南京大学自主研发的三维离散元软件Mat DEM,采用紧密堆积离散元模型对土体开裂进行模拟。在此模型中,每个离散元单元代表一定体积的土颗粒、孔隙和孔隙水的集合体。单元具有含水量属性,并采用有限差分思想计算水分运移量,实现了水分场模拟。同时,考虑水分场对土体抗拉强度等力学性质的影响,建立水分场和应力场的耦合。在数值模拟中,假定土体表面水分以一定速率蒸发,根据试验数据由含水量计算单元直径和力学参数,从而实现黏土蒸发失水、收缩和开裂变形过程模拟。数值模拟与前人室内试验结果基本一致,能较好地再现开裂过程中的各个阶段。本文为研究多场作用下土体变形破坏模拟提供了一个新的思路。

Desiccation cracks can be formed in clay soil during drying, which connects with each other to generate a network. This process involves multi-field coupling effect, including water, thermal and stress. A close-packed model is used to simulate the formation of desiccation cracks. The simulation is based on the 3D discrete element modeling software MatDEM that is independently developed by Nanjing University. In the model, a discrete unit represents an assembly of soil particles, pore and pore water. Elements in the model are assigned moisture properties, where the transport of moisture can be simulated based on the Finite Difference Method. Furthermore, the coupling of moisture field and stress field is built, which considers the influence of moisture on the tensilestrength of soil. In numerical simulation, assuming the water of soil surface evaporates at a certain rate, element diameters and mechanical parameters are calculated from moisture according the experimental data, so as to simulate evaporation, shrinkage and cracking processes of clay soil. Numerical simulation results coincide with the laboratory results, and each step of cracking process can be well simulated. This paper provides an alternative way for the numerical simulation of soil deformation and failure under multi-field effect.