Experimental investigation on damage and seepage of red sandstone subjected to cyclic thermal and cold treatment

Abstract

For geothermal mining projects in cold regions, the problems of surrounding rock and water damage caused by thermal-cold shocks have become the main factors affecting engineering stability and construction safety. In addition, the permeability and damage characteristics of the rock mass after the thermal-cold cyclic shock action are not yet known. Therefore, in this study, seepage tests of red sandstone during complete stress-strain after thermal-cold cyclic shock were carried out to analysis the change in permeability of red sandstone during progressive fracturing. Meanwhile, the permeability model considering damage was further constructed by using the damage constitutive relationship based on statistical damage theory. And found that peak stress and elastic modulus were found to decrease with temperature and cycles, and both initial and maximum permeability increase with temperature and cycles during its gradual fracture. Moreover, the theoretical curve calculated by the permeability model is not much different from the experimental curve, which can effectively characterize the relationship between permeability and damage. The research results can provide reference value for the damage assessment, repair and reinforcement of the wellbore surrounding rock structure after thermal-cold shock cycle in the geothermal engineering of cold regions.