Abstract: In order to study the shear strength and failure characteristics of the stope backfill and the surrounding rock combination,which are important for the stability of the filling stope. Taking open stoping with subsequent filling stope as the physical prototype,the backfill and surrounding rock were systematically considered to generalize the mechanical model of the cemented backfill-surrounding rock combination,and a calculation method for determining the shear resistence strength parameters of the combination based on the common tangent method of Mohr stress circle and Mohr-Coulomb strength criterion was proposed. The ANSYS numerical simulation test of the combination under different confining pressures was adopted to study the shear strength and failure characteristics of the backfill-wall rock combination with different inclination angles. The study results show that when the inclination angle of the cementation surface is 0° ~ 15°,the failure of the combination mainly occurs in the filling area,and the failure mode is tension shear composite failure. When the dip angle of the cementation surface is 30° ~ 60°,the failure of the combination occurs in the area of the filling body and the contact surface,and the failure mode is shear failure,and as the confining pressure increases,the combined surface will slip and as the cemented surface inclination angle increases,the shear failure surface gradually coincides with the combined surface. When the inclination angle of the cementaiion surface is 75° ~ 90°,the ultimate failure mode of the combination is mainly shear failure of backfill. The study results expand the method for obtaining the shear strength parameters of the backfill-surrounding rock combination,reveal the failure characteristics of the backfill-surrounding rock combination with different contact angle,and provide theoretical support for the stability analysis of the underground backfill stope.

Key words: backfill mining,cemented backfill-surrounding rock combination,shear strength,numerical simulation,failure characteristics