Effect of stress anisotropy on deformation and particle breakage of silica sand at high-pressure compression tests

Abstract

The effect of stress anisotropy on the compression behavior and particle breakage of silica sands was investigated by comparing the results from a series of high-pressure compression tests with different stress ratios (confining stress/axial stress). It was found that the stress at the yield point reduces with decreasing stress ratio, indicating that the onset of particle breakage occurs at lower mean stress for specimens with a lower stress ratio. Stress anisotropy results in more particle breakage on account of the existence of deviatoric stress. A good prediction of the relative breakage was proposed considering the influences of stress level and stress path. The relative breakage shows a linear relationship with the volumetric strain regardless of the stress path. The fractal dimension increases nonlinearly with increasing normalized mean stress/relative breakage. The parallel study on the micro-mechanical behavior of silica sands was performed using a novel miniature triaxial apparatus and X-ray micro-computed tomography (μCT). It was observed that particle breakage results in a fractal condition in silica sands with a radius below 0.4 mm. The high-pressure compression tests obtained a linear relationship between the fractal dimension and particle content for particle radius less than 0.4 mm. A hyperbolic model was also proposed to describe the relationship between the relative breakage and input work per unit volume regardless of stress path.