交通荷载作用下砂土力学性质的颗粒流模拟

采用二维颗粒流方法，建立隧道下卧层砂土的离散元数值试样．通过与室内试验的对比，标定了试样的细观参数，模拟了固结排水条件下砂土在循环等应力荷载作用下的剪切试验，分析了固结方式、平均应力、动应力水平等因素对其动力特性的影响，并从配位数和颗粒间接触力的空间分布和变化规律上对加载过程中的宏观动力特性做出了解释．模拟结果表明：应力-应变关系的非线性以及累积塑性应变与动应力水平正相关；动应力水平越高，剪胀效应越明显而高围压下剪胀效应则不明显；动应力幅值越大，砂土密实度越高，而平均应力越大，则密实度越低．

Simulating the Mechanical Properties of Sands under Traffic Loads by Particle Flow Code

The 2-dimension particle flow method is used to establish discrete element numerical samples for substratum sands of tunnels. The comparison with laboratory tests determines the micromechanical parameters for the samples. Besides, the shear tests of the sand behavior under drained cyclic loading conditions are simulated. This paper then studies the effects of consolidation process, mean normal stress and cyclic stress amplitude on the dynamic properties. Coordination number and the space arrangement and change laws of contact force between particles are described to interpret the macroscopic shear properties in the loading process. The simulation results show that the nonlinearity of stress-strain relationship, and cumulative plastic strain and the level of dynamic stress are positively correlated. As the dynamic stress level increases, the dilatancy effect is more powerful; but in high confining pressure the dilatancy effect remains subtle. As the dynamic stress amplitude rises, the dense degree of sand grows; as the mean stress increases, the dense degree decreases.