Abstract: Due to historical reasons,irregular irregular mining and excavation of small mining sites around the Gongchangling Openpit Iron Mine have resulted in the formation of a large number of shallow goafs in the Dumu mining area.Due to production needs,Xiaobeigou in the Dumu mining area is required.The empty area is blasted.In order to ensure the safety of roller drilling equipment and personnel,the stability of the empty area needs to be evaluated.Taking into account the characteristics of the geological conditions and the stability of surrounding rocks in the goaf of Gongchangling Openpit Mine,FLAC3D numerical calculations were used to carry out the static calculation of Xiaobeigou empty area and the calculation and analysis of the roller cone rig above the empty area.Studies have shown that the maximum compressive stress value at the roof after the formation of the goaf is 2 MPa,and the maximum tensile stress value at the roof is 0.25 MPa.The compressive and tensile stresses generated are not very large; The monitoring point shows that the maximum vertical displacement of the surface does not exceed 10 mm; when the equivalent load of the roller cone rig is applied to the surface danger zone 1,the maximum vertical displacement is about 0.56 mm.The maximum vertical displacement is about 0.48 mm,and the roller rig will not have a significant impact on the surface subsidence.

Key words: Goaf, Open pit iron mine, Numerical simulation, Surface subsidence