Quantitative Risk Assessment Method And Its Application For Deep Tunnel Failure At The Ashele Copper Mine

With the increase of mining depth,the mining system of deep metal mines is more complex,and the shaft and tunnel engineering is staggered with vertical shape extending thousands of meters horizontally and vertically.There are many mining areas,and dozens of stope are operating in different middle sections at the same time.For high-production mines,especially those that use medium-length hole blasting or long-hole blasting,the explosives used can be more than hundreds of kilograms or even several tons,which will cause extremely strong blast disturbance.The failure o f tunnel in deep metal mine is more complicated and uncertain in time and space.Under the condition of high stress,the failure problems of rock mass such as tunnel wall,caving and collapse caused by frequent mining disturbance become more and more prominent.Therefore,it is urgent to carry out the research on the failure risk assessment of deep metal mine tunnel,and obtain the regional failure risk assessment results of tunnel,so as to provide the basis for targeted support measures and systematic mining process regulation and control.In this paper,the deep mining area of Ashele Copper Mine is taken as the research object,and the evaluation index system of tunnel failure is constructed.On the basis of determining each evaluation index by various weighting methods,the risk assessment and prediction of tunnel failure in deep metal mine area are carried out based on fuzzy theory and normal cloud model theory.The main research contents of this paper are as follows:(1)Determination of risk assessment index of surrounding rock failure in deep tunnel and spatio-temporal unit scale of microseismic data.Through the investigation of deep tunnel failure in Ashele copper mine,the failure characteristics of tunnel are summarized and the criterion of tunnel failure level is formulated.Taking the principle of index selection,engineering layout conditions,monitoring information and tunnel failure characteristics into comprehensive consideration,three evaluation indexes of geological occurrence conditions,mining influence and microseismic data were selected to establish the evaluation index system of tunnel failure.Based on the statistical parameters of microseismic index,the classification difference characteristics of microseismic index values under different spatial and temporal scales were summarized,and the spatial and temporal selection unit of microseismic index was determined.(2)Reliability and weight analysis of the risk evaluation index for deep tunnel failure.Based on the sample data of deep tunnel damage in Ashele Copper Mine,carry out statistical analysis of evaluation indicators,correlation analysis between indicators,and correlation analysis between evaluation indicators and damage levels.Based on analytic hierarchy process,factor analysis method,entropy weight method,attribute similarity method,and game theory comprehensive weighting method,using objective and subjective weighting methods to determine the weight values of different evaluation indicators.(3)Study on comprehensive evaluation method of failure level of surrounding rock in deep tunnel.The fuzzy comprehensive evaluation method and cloud model theory were used to carry out the comprehensive evaluation of tunnel failure.The performance evaluation results of the evaluation model were obtained,and the classification performance of the model under different failure levels was analyzed.At the same time,the digital characteristics of different evaluation indexes and different damage levels of tunnel were obtained based on the cloud model,and the weighted average method of objective assignment and the maximum membership principle were adopted to determine the damage level evaluation method of"maximum membership principle+comprehensive evaluation value".(4)Failure risk prediction of deep tunnel.The failure risk assessment process and risk assessment matrix of tunnel were formulated,and the failure risk assessment method of deep tunnel suitable for Ashele Copper Mine was established,and the failure risk of deep tunnel was predicted.The results showed that:The failure risk assessment method of deep tunnel in Ashele Copper Mine can meet the need of failure risk assessment of large-scale tunnel engineering and provide strong support for ground pressure disaster prevention and control in deep mining area.