Loading rate-induced failure characteristics and fracture classification of various weathering grade sandstone

The weathering-induced changes contribute significant alteration to mechanical and failure characteristics in the rock matrix. It is crucial to evaluate the rock fracture characteristics and mechanical response under different weathering grades because prestressing rock is extremely susceptible to the effects of weathering. Consequently, this study investigates the failure characteristics and numerous generated sandstone fractures at various weathering degrees under quasi-static loadings. Brazilian tests were conducted under different loading rates (LR= 0.001 kN/s, 0.01 kN/s, 0.1 kN/s and 1 kN/s). The findings demonstrated that sandstone tensile strength is equally susceptible to loading rate and weathering grade. The tensile strength of fresh, slightly weathered and moderately weathered sandstone increased by 20%, 54%, and 52%, respectively, with an increase in loading rate from 0.001 to 1 kN/s. The fracture angle (FA), fracture maximum deviation distance (FMDD) and fracture deviation area (FDA) of fresh and moderately weathered sandstone decrease with an increase in loading rate. FMDD of slightly weathered sandstone increases slightly as compared to FA and FDA. Additionally, the results indicate that the fracture length (FL) of slightly and moderately weathered sandstone increases as the loading rate increases, whereas the FL of fresh sandstone decreases as the loading rate increases. Overall, it can be concluded that sandstone strength is affected not only by the loading rate but also by the weathering grade. Based on the laboratory failure characteristics, the geometrical trajectory is divided into single central line fracture, double central line fracture, central-non-central line fracture and non-central line fracture.