Determination Of Rock Mass Mechanical Parameters And Optimial Selection Of Mining Method In A Metel Mine

In this paper,the mechanical properties of the rock mass,the optimization of mining method and the structure parameters of the stope in a large metal mine are studied.On the basis of field joint investigations,laboratory tests,roadway displacement and ground stress measurement are carried out,by combining the theoretical analysis for estimating mechanical parameters of rock mass,the back analysis of the roadway displacement,the multi-objective decision method and the numerical simulation calculation,we determine the mechanical parameters of rock mass accurately,and carry out the optimal selection of mining method and optimization of stope structure parameters.The main researches are as follows:(1)The joint structures of the rock mass are investigated by scanline method,various rock mechanical parameters are obtained through laboratory tests,and ground stress and roadway displacement are measured in the field.We obtain the physical and mechanical characteristics of ore and surrounding rocks,the distribution of the joint structure and ground stress of the mining area.(2)The ranges of rock mass mechanical parameters based on the method of GSI quantification and correction are preliminarily determined.On the basis of the previous research results,The Rock Block Index(RBI)is replaced by Rock Block Rating(RBR).Four parameters of RBR,d,SCR and Jc are used to quantify GSI value.In order to overcome the shortcomings of the GSI system,the correction method of the GSI value is provided.Thus,a new method of quantifying the GSI value is completed.(3)A three-dimensional entity model and a block attribute model are built based on SURPAC software.The Java language is used to edit the program that converts the SURPAC block model into a FLAC3D numerical model.The variation laws of ground stress with depth in the direction of X,Y and Z axis are obtained,the initial ground stress field in the mining area is reproduced by using the stress boundary method.(4)The genetic algorithm(GA)and FLAC3D connection program based on the Hook method are developed by using the VC++ language.Based on the range of mechanical parameters of rock mass and field displacement measurement data,the intelligence back analysis of displacement is carried out by combining(GA with FLAC3D,so more accurate mechanical parameters of rock mass are determinated.(5)According to the technical equipment level of the mine and the geological conditions of the ore deposit,the application conditions of all mining methods are analyzed,and 3 kinds of feasible mining methods are selected preliminarily.A multi-objective decision index system is established by comprehensively considering the multiple aspects that affect the selection of mining method.The membership degree matrixs of quantitative factors and qualitative factors are established by using the range transformation principle and precedence relation binary contrast method.We utilize the Fuzzy Analytical Hierarchy Process(FAHP)to build the subjective weight matrix and apply the Entropy Weight Method to calculate the objective weight matrix.A principle of obtaining subjective-objective combination weight matrix is improved by introducing the Grey Relational Analysis method(GRA).On this basis,the best mining method is selected.(6)On the basis of the design principle of selected mining method,Mathew method and theory of elasticity,stope structural parameters of scheme 14 are selected.Through FLAC3D numerical simulation analysis,we get the stope stability factor for each scheme.Considering the stope stability factors,technical and economic factors,we choose the best stope structural parameter scheme with high economic efficiency by using Technique for Order Prefcerence by Similarity to Ideal Solution(TOPSIS)method.This paper solved the problem of determining the exact parameters of rock mass in geotechnical engineering,and explained method to obtain the subjective and objective combination weight in the optimal selection of the mining method and stope structural parameters.The research ideas and research results are of great value for determining rock mass mechanical parameters and optimizing mining methods.