土工格栅加筋砂土三轴试验离散元细观分析

以室内单层加筋三轴试验结果为基础,建立离散元PFC3D三轴试验数值模型,并与室内三轴试验结果进行验证对比,分析加筋层数变化对抗剪强度指标及细观参数的影响,探讨加筋土接触力的变化规律及筋材加筋作用的宏细观机理。研究结果表明:加筋三轴试样的峰值强度、黏聚力和内摩擦角随着加筋层数的增加而增大,但是其增幅会逐渐减弱,并且三轴试样在低围压条件下的加筋效果比高围压时要显著。三轴试样颗粒滑动比的数值随着轴向应变的增加发生了显著的起伏变化,反映三轴试验过程中发生了明显的接触滑移和旋转现象。由于筋材的摩擦嵌固约束作用,加筋试样中部区域的孔隙率和滑动比数值相对波动较小,对应中部外侧周围的接触力明显小于纯砂三轴试验情况,加筋材料发挥了扩散应力增强约束砂土的加筋作用。

Mesoscopic analysis of reinforced sand triaxial test using PFC3D

On the basis of the results of single reinforced triaxial test in the laboratory, the discrete element PFC3D triaxial test numerical model is established, and the results are compared with the laboratory triaxial test results. The influence of reinforced layers changes on shear strength parameters and the microscopic parameters is analyzed, and soil particles contact force variation and macroscopic-mesoscopic mechanisms of geosynthetics reinforcement effect are discussed. The results show that reinforcement triaxial specimen peak strength, cohesion and internal friction angle increase with the increase of reinforcement layers, but the increase will gradually weakened, and the reinforcement effect of the triaxial specimen under low confining pressure is higher than that of the high confining pressure. The sliding fraction value of the triaxial specimen has a significant fluctuation with the increase of axial strain, which reflects the obvious contact slip and rotation in triaxial test. Due to the friction restrain effect of geosynthetics, the fluctuations of porosity and sliding fraction of reinforced specimen in the central region are relatively small, and the contact force corresponding to the middle part of the outer periphery is obviously less than that of sand triaxial test. The reinforcement materials play a role in diffusing stress and enhancing reinforcement of sandy soil.