Discrete element mesoscopic study on interface characteristics of coarse-grained soil-geogrid in seasonal frozen soil area

Abstract

In order to seasonally frozen regions, significant temperature fluctuations affect the mechanical stability and long-term durability of reinforced soil engineering in cold areas by changing the mechanical properties of the reinforced soil interface. This study uses the discrete element method PFC^3D software. A numerical simulation of the direct shear test was carried out for coarse-grained soil-geogrid indoor direct shear test at-5 ℃. The evolution process of macro and micro characteristics of geogrid reinforced coarse-grained soil in direct shear tests, such as single deformation force, porosity change, displacement and rotation of coarse-grained soil, and force chain stress field inside the soil, is revealed. The accuracy and practicability of the model are verified by comparing the simulation result with the laboratory test result. The results show that under the condition of-5 ℃ low temperature, with the increase of shear displacement, the deformation is gradually obvious, and the deformation of the longitudinal rib is significantly greater than that of the transverse rib. An in-depth analysis of the porosity changes of different sections inside the soil shows that the porosity decreases with the increase of shear displacement, and the porosity on the shear surface and below shows an asymmetric distribution pattern. The shear displacement is mainly concentrated around the shear surface, and the displacement is characterized by high left and low right. As the shear proceeds, a centrally symmetrical arch structure is formed inside the soil. The stress field of the soil is further explored. The strong chain is initially distributed along the wall to create a low-stress zone. After the stress peak, the contact force between the particles decreases, and the force chain is distributed along the diagonal. This distribution feature is closely related to the applied horizontal thrust. The research findings provides a theoretical explanation for the reinforcement mechanism of coarse-grained soil from the microscopic point of view and provides data support for the design parameters of reinforced soil engineering in seasonal frozen soil areas.

Keywords

seasonal frozen soil / geogrid / discrete element / direct shear test / macroscopic and mesoscopic characteristics