Abstract: Underground mining may induce the movement of rock strata，leading to the instability of the waste dump and threatening the safety of the mining area. To achieve the goal of balancing safety and economy，a numerical simulation method is adopted to analyze the influence of filling mining on the stabili⁃ ty of the waste dump and demonstrate the feasibility of the collaborative layout. Based on the geological ex⁃ ploration data and mining design of the mining area，a three-dimensional numerical model including open�pit waste dumps，underground stopes and filling bodies was constructed to simulate the deformation law of rock mass under different filling body strength（0.5~2.5 MPa）working conditions. The model adopts the Mohr-Coulomb criterion，sets the staged underground mining and the strength gradient change of the filling body. The model focuses on monitoring the displacement field，stress field，plastic zone expansion of the waste dump and the roof settlement of the underground stope. The quantitative relationship between the strength and stability of the filling body is established through the comparison of multiple working condi⁃ tions. The results show that: ①In terms of horizontal deformation，the horizontal deformation in the X/Y di⁃ rection has low sensitivity to the strength of the filling body（0.5~2.5 MPa），and the maximum tensioning values are 80 and 120 mm respectively; In terms of settlement control，the settlement in the Z direction is affected by the strength of the filling body. When the strength is 0.5~1.0 MPa，the maximum settlement eaches 155~212 mm. When the strength is 1.5~2.5 MPa，the settlement amount drops to 142~136 mm. When the strength is greater than 1.5 MPa，the decrease in settlement slows down（only reducing by 6 mm）. ② In terms of shear strain and stress field，the strength variation of the filling body has a weak influence on the shear strain increment and the distribution of the surface stress field of the waste dump. The shear strain increment is basically consistent with the original state，indicating that the main controlling factor for the base deformation of the waste dump is vertical settlement. ③ In terms of the plastic zone and stability，when the strength of the filling body is not less than 0.5 MPa，the range of the plastic zone of the waste dump and the formation is relatively small，and the influence on the overall stability is controllable. ④Regarding the roof settlement of the stope，the roof settlement shows a decreasing trend with the increase of the strength of the filling body. The extreme values of settlement are all located directly beneath the waste dump，revealing that the load of the waste dump has a reverse disturbance effect on underground mining. By controlling the strength of the filling body to be no less than 1.5 MPa and setting up open-pit waste dumps within the mobile zone，the coordinated and safe mining of open-pit and underground can be achieved.

Key words: waste dump, filling strength, numerical simulation, surface subsidence