Abstract: In view of the problem that the deformation and damage of the slope seriously affect the safety production of the openpit mine in the process of openpit mining,a threedimensional model of the high slope of huangjiashan mountain in Taihe Openpit Iron Mine of Chongqing Iron and Steel Group Co.,Ltd.is established by using the numerical simulation method and MidasGTSNX software,and the numerical simulation analysis of the stressstrain,displacement and the change of the safety coefficient in the process of excavation and unloading is carried out.The results show that in the process of excavation and unloading of slope rock mass,with the deepening of stope and the increase of slope angle,the plastic stress zone gradually expands to the inside of slope rock mass,and the plastic strain breakthrough area is formed between the weathered broken layer and the upper moraine soil layer,and the failure surface is formed.After the excavation,shear failure occurs at the foot of the whole slope,tensile failure area is formed at the back edge of the slope top,and the moraine soil layer at the upper part of the slope forms "seat slip" sliding.The safety factor of slope decreases gradually with the downward excavation process,and finally reaches 1.15,which is slightly lower.In the later mining process,it is necessary to reinforce the weathered broken rock and moraine soil in the middle and upper part of the slope.

Key words: Excavation and unloading of high slope,Weathered broken layer,Strength reduction,Method safety and stability