Experimental and numerical research on fracture behaviors of sandstone under different loading rates

The macroscopic deformation process of rock is the external performance of microscopic damage in essence, and research from the macro and micro perspectives can effectively reveal the failure mechanism of rock. To further investigate the fracture behaviors of yellow sandstone disc specimens under different loading rates, seven groups of Brazilian disc splitting tests with different loading rates from 1 × 10–6 to 1 × 10–4 s–1 were carried out. A systematical investigation of loading rate effect on macroscopic mechanical responses and microscopic damage characteristics has been conducted from the stress–strain relationship obtained from material testing system, from damage three-dimensional localization based on acoustic emission techniques, and from fracture morphology by scanning electron microscope. In addition to laboratory experiment, parallel bond models of different grain size distribution indexes based on particle flow code were established. The coupling effect of loading rate and grain size distribution index was further analyzed. The results interpret that the effect of loading rate on rock fracture behaviors is determined by the process of crack initiation, propagation and coalescence, and it is also affected by distribution of different size grains. The differences of rock fracture behaviors under different loading rates were discussed from the mechanism of energy input and dissipation. The research have actual significance for stability design and evaluation of rock excavation engineering.