基于离散元的南海软粘土剪切变形模拟

软粘土剪切变形是决定海洋构筑物、管线安全存在的重要因素,离散元能有效模拟粘土剪切变形。通过对南海神狐海域原状软粘土开展固结不排水三轴试验,得到离散元模拟所需宏观剪切强度参数指标；采用试错法调整细观参数使得双轴压缩模拟结果与室内试验相吻合,标定出一组适用于南海软粘土的细观参数组合。离散元模拟结果得到,在应变达到5.3%时,土体发生破坏,形成一条与X轴反方向为49°的剪切带；应变增加到10%时,倾角增大到57°。测量圆对剪切带内外的应变进行监测得到,剪切带内土体初始应变较大,在达到4%应变后不再继续发生变形；剪切带边缘区域,土体应变持续增大；剪切带外应变较小。一般的室内三轴试验无法得到剪切带内外土体应变变化定量数据,离散元模拟是对室内三轴试验的重要补充。

Shear Deformation Simulation of Soft Clay in South China Sea based on Discrete Element Method

The shear deformation characteristics of soft clay are important factors determining the safe existence of marine structures and pipelines, and discrete elements method can effectively simulate clay properties. Through the consolidated-undrained (CU) triaxial testing, we can obtain the shear strength parameters and other parameters required for discrete element simulation. A set of meso-parametric combinations suitable for soft clay in the South China Sea was calibrated by trial and error method. The results of biaxial compression simulation were consistent with laboratory tests. The discrete element simulation results show that when the strain reaches 5.3%, the soil damage and a shear zone with a negative X direction of 49° is formed. As the strain increases, the shear zone inclination angle increases. A small angle of deflection occurs in the main dominant direction of the contact normal direction, the normal contact force, and the tangential contact force during the shearing process. By setting the measuring circle to monitor the strain inside and outside the shear band, the initial strain of the soil in the shear band is large, and the deformation does not continue after reaching 4% strain and the soil strain continues to increase in the edge region of the shear band. The strain outside shear band is small. The general laboratory triaxial test can not obtain quantitative data of soil strain changes inside and outside the shear band, so the discrete element method is an effective supplement to the laboratory triaxial test.