Grain Deformation of Fractured Sandstone and Stokes Local-rotation of Material Line

The movement and deformation of mineral grains in rocks control the failure behavior of rocks. However, at high resolution, the physical and mechanical behavior of three-dimensional microstructures in rocks under uniaxial compression has not been characterized. Here, in suit XCT (4.6 um) has been applied to investigate the behavior of mineral grains of sandstone -- movement, rotation deformation and the principle strains obtained by deformation gradient tensor constructed with three principle axial vector representation of grain, indicating that the behavior of grains between the fracture and the non-fracture zone are different. For further investigate the behavior of grain cluster, the material lines are used to obtain the Stokes local rotation, namely shear strain. The finding is that: 1. the shear strain is periodic in the radial direction. 2. on average sense, the positive shear strain and negative shear strain have local concentration features.