Influence of coupled water and thermal treatments on the fracture characteristics of a typical sandstone

Abstract

Understanding the fracture behavior of rock after coupled water and thermal environment is important for many geotechnical projects. The influence of coupled water and thermal treatments on the mode-I and mode-II fracture toughness and characteristics of sandstone was investigated using notched deep beam specimens. The experimental results indicate a significant reduction in both mode-I and mode-II fracture toughness of sandstone under varying soaking temperatures. As the water temperatures increase, a slightly rising trend is observed in both mode-I and mode-II fracture toughness within the studied soaking temperature range. At lower soaking temperatures, sandstone exhibits typical brittle characteristics, which gradually transition to ductile properties as the temperature increases. Based on the Maximum Tangential Stress (MTS) criterion, the predicted values of mode-II fracture toughness and the fracture process zone were discussed. The results show that both the GMTS and MTS criteria exhibit inaccuracies in predicting the Mode-II fracture toughness of sandstone treated at different soaking temperatures. However, the GMTS criterion, which incorporates T-stress, demonstrates smaller errors compared to the MTS criterion. The study shows that the radius r0 of the fracture process zone is not a constant under both mode-I and mode-II loading conditions. The calculation of the fracture process zone radius r0 in the MTS criterion requires further theoretical and experimental study.