Microscopic mechanism analysis of temperature influence on rock salt and thermal damage evolution of surrounding wall in underground salt cavern

Underground salt caverns have been used as gas storage for several decades. To explore the utilization of salt cavern in deep underground energy storage, one of the key issues is the mechanical characteristic of rock salt responses to high-temperature. In this study, the influence of temperature variations on rock salt is investigated through an integration of high-temperature uniaxial compression experimental test and high-temperature triaxial compression test. The characteristics of microcracks in rock salt are performed at different temperatures by DEM simulations. The results indicate the high temperature soften the strength of rock salt and induce thermal-cracking. The dilation point is analyzed from a microscopic perspective, and is interpreted as a turning point during the process, which the accumulated sliding energy gradually diffuse to the boundary energy. Additionally, a novel hybrid continuum-discrete coupling model is employed to reveal the mechanism of uncoordinated deformation of salt cavity surrounding wall subjected to operation conditions. The temperature influence exerts effect on temporal and spatial variations of salt cavity. The thermal damage evolution is prone to develop at interlayers, rather than the interface between the pure rock salt and interbedded impurities layer.