A damage model of rock-concrete composite in coal mine underground reservoirs

In order to ensure the stability of rock-concrete composite (RCC) in coal mine underground reservoirs (CMURs), the theoretical damage model of the RCC was constructed in the present work. Considering the deformation compatibility between two different media of RCC on loading, the damage variable of RCC is deduced based upon the relationship between the damage variables of rock and concrete following the strain equivalence principle. Adjudging the failure of rock and concrete by different strength criteria, a damage model of RCC in coal mine underground reservoir (RCCD model) was developed. The experiments on the uniaxial and triaxial compressions of rock, concrete and RCC were used to validate the proposed damage model. The RCCD model curves exhibited four different periods in triaxial compression. The correlation coefficients between the values of RCCD model and the test values were determined to be 0.959, 0.981, 0.998 and 0.996. In addition, the correlation coefficients of rock and concrete were higher than 0.959. Moreover, the correlation of the parameters in the RCCD model was analyzed. The sensitivity of Weibull distribution parameters, height ratio coefficient, elastic modulus ratio and tension compression ratio of RCC were discussed. The study illustrates that the proposed RCCD model can satisfactorily characterize the mechanical characteristics of RCC under various loadings.