Strength deterioration study of coal and rock mass affected by coupled-crack

To establish the relationship between the scheme of coupled-crack and strength deterioration for the coal and rock mass as the target, the interaction of injection water measure and blasting measure are defined as coupled-crack, and the coupled-crack mechanism is analyzed, giving the crack propagation criterion for the implementation of coupled-crack technology. Strength deterioration analysis method of fluid-solid coupling model affected by explosion is put forward. By using numerical simulation method, we establish the models for injecting water and obtaining explosion load, axially load is applied after finishing explosion loading, the strength degradation degree of overall model at different coupled-crack schemes is analyzed. The results show that: the essence of coupled-crack is that detonation gas and shock wave formed by explosion spreads in softened coal and rock mass, coupled-crack effect is greater than the simple superposition of basting and injection water;Improve water pressure can increase the strength degradation rate of coal and rock mass, model strength has a significantly decreased with the increase of drill diameter (explosion). The relationship between the coupled-crack parameters and strength deterioration degree of f is obtained, the damage degree of coal body caused by injection water pressure of explosive consumption is quantitatively evaluated. In engineering practice, the strength of coal mass from steeply dipping extra-thick coal seam after coupled-crack is 5.48 MPa, which has a decreased by 40.07% compared with the implementation of injection water. The working face recovery rate meets the requirements of national standards for thick coal seam, which realizes the objective of improving the top coal recovery rate, providing experiment method and basis for the quantitative evaluation of coupled-crack effect. ©, 2015, Academia Sinica. All right reserved.