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

Abstract

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.

Keywords

• loess
• micromechanical characteristics
• biaxial test
• flexible cluster
• discrete element simulation