原状及重塑黄土双轴试验微观力学特征离散元模拟

黄土作为一种特殊的颗粒材料，微观上颗粒组成的结构决定了其力学特性。原状及重塑黄土因结构的差异而具有不同的力学特性。针对黄土结构性如何影响其力学特征这一基本问题，开展基于电镜扫描获取细观颗粒信息，同时考虑颗粒形状、颗粒破碎可能性进行建模的离散单元法进行原状黄土和饱和重塑土在恒定应变速率双轴试验下的宏观力学和细观力学性能研究。研究结果显示:试样微观结构的差异对变形破坏过程产生显著影响。当轴向应力较低时原状黄土及重塑黄土力链多分布于大型骨架颗粒附近，随着轴向应力增加，原状黄土力链形成网状图案但仍具备主要传导区域，重塑黄土无明显主要传导区，呈现均匀网状。原状土及重塑土骨架颗粒簇周围多形成张拉裂隙，剪切裂隙多数形成于骨架颗粒簇内部，又以颗粒簇相互挤压接触时最为明显。使用该建模方法，可以有效反映原状及重塑黄土由于内部结构组成差异导致相同应力条件下产生的不同内部应力状态。基于以上研究结论，给出了黄土结构性对宏观强度影响的微观解释。研究成果可为黄土地区地质灾害防治提供一定依据。使用该建模方法，可以有效反映原状及重塑黄土由于内部结构组成差异导致相同应力条件下产生的不同内部应力状态。基于以上研究结论，给出了黄土结构性对宏观强度影响的微观解释。 

Discrete element simulation study on micromechanical characteristics of undisturbed and remolded loess in biaxial test

Loess is a special granular material, and its mechanical properties are determined by the microscopic structure of granules. The undisturbed and remolded loess have different mechanical properties due to the difference in structure. In order to solve the basic problem of how the structural properties of loess affect its mechanical characteristics, based on scanning electron microscopy (SEM) to study the macroscopic and microscopic mechanical properties of undisturbed loess and saturated remolded loess under constant strain rate biaxial test, while considering the shape of particles and the possibility of particle breakage. The simulation results show that when the stress is low, the undisturbed loess and the remolded loess force chains are mostly distributed near the large framework particles. With the increase of stress, the undisturbed force chains form a network pattern but still have the main conduction region, while the remolded loess has no obvious major conduction region and presents a uniform mesh. Under the same confining pressure and strain, the number of cracks in the undisturbed loess is lower and they are concentrated in the shear zone. The number of cracks in the remolded loess is more but more uniform.Tension cracks are mostly formed around the clusters of undisturbed loess and remolded loess. Shear cracks are mostly formed inside the clusters of framework particles, and the most obvious is when the clusters of particles are in contact with each other. Using this modeling method can effectively reflect the different internal stress states of undisturbed and remolded loess under the same stress condition due to the difference in internal structure composition. Based on the above research conclusions, a microscopic explanation of the influence of loess structure on the macroscopic strength is given. The research results can provide a certain basis for the prevention and control of geological disasters in the loess area.