Microscale Analysis of Direct Shear Test Using Discrete Numerical Method

Microstructure and micromechanics play significant roles and are considered to govern the macroscale behavior of granular soils. Laboratory experimental methods such as X-ray tomography and solidified-then-sectioned method are the traditional way for microscale analyses. But these methods are usually time consuming, expensive, or exceedingly difficult to perform. In the current study, a series of three-dimension discrete numerical simulations are performed to simulate the direct shear tests with different initial porosities and confining stresses. Particle behaviors (particle rotation and displacement) are investigated. Information of contact parameters (contact normal and contact force) which is not readily observable in the laboratory is obtained. Statistical analyses are performed and spherical histograms are employed to present the distributions of three-dimensional contact normal and normal contact force. Rotation of the principal stress directions, which is proposed theoretically and observed experimentally by some previous researchers, is successfully captured.