Research on the inherent mechanism of rock mass deformation of oil shale in-situ mining under the condition of thermal-fluid-solid coupling

With the gradual maturity of in-situ mining technology of oil shale, environmental geological problems such as ground subsidence after mining become increasingly important. The existing researches focus more on the improvement of mining technology, but less on the deformation of oil shale after mining. In this study, various experiments are used to test the pore characteristics and mechanical properties of oil shale with temperature. It is found that parallel bedding macro fractures are formed during oil shale pyrolysis, and the mechanical properties change differently in parallel and vertical bedding directions. The anisotropy of mechanical properties of oil shale is related to the anisotropy of pore structure for the first time to explains the mechanism of deformation. Moreover, the constitutive model of in-situ mining deformation of oil shale is established through statistical damage mechanics combined with pore structure. The deformation of in-situ mining of oil shale under thermal-fluid-solid coupling condition is studied by combining the constitutive model with multi-field coupling numerical simulation. The results show that the compression deformation of oil shale is about 6.5 cm per meter at 200 m underground, and the impact of in-situ mining on geological environment is less than that of traditional mining methods.