Micro-macroscopic mechanical behavior of frozen sand based on a large-scale direct shear test

Abstract

The mechanical properties of frozen soil are of utmost importance for infrastructure development in cold regions, and the microscopic characteristics play a vital role in revealing the mechanism of strength and deformation evolution. In this study, the mechanical behaviors of frozen sand at various negative temperatures are investigated by a self-developed temperature-controlled large-scale direct shear apparatus. The shear stress-shear displacement curve, dilation curve and shear strength characteristics at different negative temperatures and normal pressures are analyzed. According to the test results, as the cooling temperature decreases, the cohesion and internal friction angle of frozen sandy sample both increase significantly, and the shear dilatation tends to be larger. The brittle behavior of frozen sand becomes more obvious at lower temperatures. Then, a discrete element method (DEM) model is established to investigate the microscopic mechanical properties of frozen sand in the direct shear test. The particle movement, force chain evolution, and shear surface development during the shearing process are analyzed. The simulations of the DEM model can well explain the microscopic mechanism of the macroscopic strength and deformation law of frozen sandy soil. It is hoped that the research results can provide a reference for the DEM application in frozen soil mechanics.