Abstract: In order to study the deformation characteristics of the side-wall rock of underhand drift under overlaying filling pressure, and based on the comprehensive analysis of the forming criterions of movable block body in connecting between the backfill body and underhand cut-and-fill drift, the mechanical effects of the backfill body on the underhand cut-and-fill drift is analyzed with elastic theory.The results show that the effects of the backfill body on the stability of the rock of underhand cut-and-fill drift relate with the aspect ratio of the underhand drift, the mechanical properties of the orebody, and the dip angle of the movable rock mass's sliding surface.The deformation and failure mechanism of the movable block body under filling pressure was discussed, and the methods for calculating the stability coefficient of movable block body and the force on the movable block body from the backfill body were put forward.Finally, the applied effect of the method is verified with a practical engineering case in Wushan copper mine.

Key words: Backfill body, The underhand cut-and-fill drift, Stability, Movable block body, Side of stope