含微生物气泡高饱和砂土循环三轴剪切CFD-DEM模拟

Cyclic Triaxial Shear Tests on Highly Saturated Sand Containing Microbial Bubbles with CFD-DEM Coupling Method

摘要:

为探究砂土液化的微观机理，根据室内试验中微生物反硝化反应气泡的生成速率，建立数值模拟的时效性关系，分别制取微生物处理0天、2天、3天和5天的高饱和砂土试样，采用CFD-DEM耦合方法模拟不同工况下砂土试样的循环三轴不排水剪切试验。依据砂土试样的力链分布、抗液化振次、孔压比、轴向应变和力学配位数在加载过程中的变化情况，从宏微观角度分析砂土试样的抗液化能力。模拟结果表明：含微生物气泡高饱和砂土的抗液化强度较饱和砂土有所提升；随着微生物处理时间的增加，砂土试样的饱和度降低，孔压比和轴向应变的累积变慢，抗液化能力增强。

Abstract:

To investigate the microscopic mechanism of sand liquefaction, this study proposes a time-effect relationship according to the generation rate of bubbles in indoor microbial denitrification test. Highly saturated sand samples were treated with microbiological method for 0, 2, 3, and 5 days. The samples were subjected to cyclic triaxial undrained shear tests by CFD-DEM coupling method under different working conditions. Changes in force chain distribution, vibration time, pore pressure ratio, axial strain, and mechanical coordination number of the samples during the load process were determined to study their liquefaction resistance. Numerical results show that the liquefaction resistance of the highly saturated sand samples containing microbial bubbles is higher than that of fully saturated sand. With increasing treatment time, the saturation degree of the samples decreases but their liquefaction resistance increases; moreover, the pore pressure ratio and axial strain increase slowly.