Risk Assessment Of Slopes At Hualian Zinc-Indium Open-pit Mine

The Manjiazhai open pit has been extensively mined since 2004.The lowest mining elevation is 910 m,the highest elevation is 1340 m,and the maximum height of the slope is 430 m.On the one hand,the slope stability of the stope decreases with the increase of the slope height.On the other hand,the slope stability is affected by the structural characteristics of the rock mass,the physical and mechanical properties of the rock and soil,the geological structure,the groundwater,the atmospheric precipitation,and the artificial opening.Excavation disturbance and many other factors,and for the mine slope,the above factors are not static,which leads to the change of slope stability;the slope has occurred 4 times of landslide since 2008,landslide The main range is F0 fault upper plate(ie west of F0 fault),elevation range of 1350m-1050 m,and the surface deformation is more serious between the 31-91 exploration line.The landslide body poses a major safety hazard to the mining and stripping of the Manjiazhai mining site.Therefore,the risk assessment of the Dongbang slope of Manjiazhai must be carried out.The main research contents of this paper are:(1)Establishment of an evaluation indicator system.Through on-site investigation,comprehensive consideration of rock mineral composition and geological structure surface,water,engineering disturbance,early warning monitoring and other factors on the stability of slope,combined with the accident tree model and expert experience to cluster analysis of indicators,establish Manjiazhai East State slope risk assessment index system,which includes five aspects: internal factors,bad geology and climate,and mining process impact.(2)Research on the calculation method of evaluation index weights.Establish qualitative and quantitative evaluation criteria for entropy weight method and AHP method.The objective weight and subjective weight of the evaluation index are calculated by the entropy weight method and the AHP method respectively.According to the principle of maximum optimality of the target weight matrix,a synthetic model of objective weight and subjective weight is established,and the comprehensive weight of the index is calculated.(3)Research on risk assessment model.The TOPSIS risk assessment model isestablished,and the Euclidean distance between the optimal positive ideal solution and the optimal negative ideal solution is calculated.The fit degree is calculated according to the distance,and the fit degree is used to judge the state of the stability of the Dongbang slope.(4)Analysis of the degree of influence of risk factors.The safety status of the Dongbang slope of the Manjiazhai open-pit mining site is 0.6629,and the risk level is“dangerous state”.From the comprehensive weighting of indicators,it can be seen that F0 fault control,rock compressive strength,final slope angle,rock occurrence,water influence,blasting vibration,mining sequence,rock mass weathering,etc.are the risk factors that have great influence.(5)Research on risk management measures.The SLOPE/W,SEEP/W,and QUAKE/W analysis modules in Geo Studio are used to calculate the stability of the slope in self-weight,groundwater,rainfall,and seismic conditions,and the hydraulic system is checked for hydraulic system.The risk control measures are determined based on the analysis results.