土工袋双轴压缩的离散元数值模拟

鉴于土工袋材料介质不连续性的特点,采用离散元法模拟土工袋双轴压缩试验,从细观角度分析土工袋的力学特性。通过蒙特卡洛随机算法生成一定颗粒级配的土颗粒样本,计算时土颗粒间采用弹簧-阻尼器-滑块接触模型,袋子颗粒间采用皮筋-阻尼器接触模型。计算结果表明:土工袋的极限强度远大于无袋子土体的极限强度,土工袋破坏时的总体变形远大于无袋子土体破坏时的总体变形,且袋子颗粒间的张力呈非均匀分布;土工袋应力-应变的数值模拟结果与理论推导公式计算值吻合较好;竖向外力作用下,土工袋内部颗粒间力链由环状均匀分布向大主应力方向发展,颗粒位移呈对称性向两侧扩散,且袋子破坏是土工袋达到极限强度的直接原因。

Numerical simulation of a soilbag under biaxial compression using discrete element method

Due to the discontinuity of soilbag materials, experiments of a soilbag under biaxial compression were modeled using discrete element method, and the mechanical characteristics of the soilbag were analyzed on a mesoscopic level. Monte-Carlo algorithm is introduced to randomly generate an assembly of soil particles with a certain grain composition. The contact between soil particles is simulated by a combination of a spring-dashpot-slider model, while the contact between bag particles is simulated by a rubber band-dashpot model. The results show that the bearing capacity of the soilbag is much higher than that of soil without a bag. When failure occurs, the overall deformation of the soilbag is also far higher than that of soil without a bag, and the tension between particles has a non-uniform distribution. The stress-strain relationship obtained from simulations agrees well with the theoretical formula. Under vertical loads, the intergranular force chains develop from the uniform circular distribution to the direction of the large principal stress, while the soil particles move to the both sides. Bag breakage is the direct reason for the soilbag to reach the ultimate strength.