A study on the effect of crack orientations, crack types and SHPB characteristics on the failure behaviour of pre-cracked sandstone rock specimens

Abstract

The present study aims to understand the experimental and numerical behavior of intact and pre-cracked fine-grained sandstone specimens under indirect dynamic tensile loading conditions. The dynamic experimental analyses are carried out using the split Hopkinson pressure bar (SHPB) device to determine the tensile strength of sandstone rock. In addition to the dynamic tests, the physical, petrological, and mechanical tests under static loading of the sandstone rock are also studied. Thereafter, a three-dimensional (3D) finite element (FE) numerical model is developed, and a strain rate-dependent modified Drucker Prager constitutive model is used to validate the numerical model with the indirect dynamic tensile experimental test results. The validated parameters are then used to determine the behavior of pre-cracked sandstone specimens through numerical simulations. Two sets of numerical models with diametral cracks and cross-sectional cracks are introduced into the intact rock specimens. The orientation of the crack is changed from 0° to 90° and the numerical analyses are performed for 0°, 30°, 45°, 60°, 75° and 90° crack orientations with respect to the loading axis of the bars in the SHPB setup. Along with crack orientations, the loading rate is changed with varying gas gun pressures for the two sets of numerical models. The stress-strain responses are retrieved from the center and tip of the pre-crack introduced in the sandstone specimen. A comparative analysis is conducted for the responses obtained at the center and tip of the diametral and cross-sectional cracks and the results are stated herein.