基于离散元的南海软黏土剪切变形模拟

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

软黏土剪切变形是决定海洋构筑物、管线安全存在的重要因素,离散元能有效模拟黏土剪切变形。通过对南海神狐海域原状软黏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黏土的细观参数组合。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 of soft clay is an important factor in determining the safety of marine structures and pipelines. Discrete elements can effectively simulate clay shear deformation. Through the consolidation and undrained triaxial test on the original soft clay in the South China Sea, the macroscopic shear strength parameters required for discrete element simulation were obtained. The trial and error method was used to adjust the mesoscopic parameters to make sure that the biaxial compression simulation results were consistent with the laboratory tests. A set of mesoscopic parameters were customized suitable for the soft clay in the South China Sea. The discrete element simulation results show that when the axial strain reached 5.3%, the soil was destroyed and a shear band was formed in 49° opposite to the X axis. When the strain increased to 10%, the inclination increased to 57°. 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 was found large, and the deformation stopped after reaching 4% strain. The soil strain continued to increase in the edge region of the shear band. The shear band outer strain was small. Commonly used indoor triaxial tests are unable to obtain quantitative data of soil strain changes inside and outside the shear band. The discrete element simulation is an important supplement to the indoor triaxial test.