Stability Analysis Of Complex Cracked Surrounding Rock And Pillar In Integrated Mining Area

With the decrease of the gold mining industry grade, low-grade residual orebody nearby goaf has its economic value of mining. The existence of a large number of goaf leads to the deterioration of the mining condition, and it’s easy to cause the problems like the instability of roadway, deformation and failure of pillar and the collapse of stope, which is a serious threat to the safety of mining operation personnel and equipment. How to realize the mining safety of the residual orebody nearby goaf is the problem urgently to be solved in mining enterprises.Taking the residual ore body in integrated mining area of a gold mine as the research object, on the basis of comprehensive analysis of domestic and foreign data, and by using the methods of field investigation, theoretical study, numerical analysis and engineering verification, this paper has researched on the key problems on stability of complex crushed surrounding rock and pillar, which creates the safe environment for mining complex broken residual orebody and guide the safe mining of residual orebody. The main research results are as follows:(1) Through the field integration of the rock mass in the mining area, the distribution characteristics of rock mass joints and fissures has been explicit. Two main types of rock mass quality has been classified and evaluated using the basic quality of rock mass classification method(BQ) and the mechanics of rock mass quality classification(RMR).(2) Using plate crack structure theory and numerical simulation method to analysis mining stress change rule of surrounding rock and safe status of crushing plate crack rock roadway. The result shows that the change of stress surrounding roadway is most significant when next phase of the ore was mined; mining stress is the cause of instability on upper roadway beyond ultimate stress.(3) On the basis of mechanical model analysis and orthogonal numerical calculation, the factors sensitivity that effect on roadway safety coefficient(F) rank from high to low as joint spacing, roadway depth, distance between roadway and stope. Using the method of multivariate nonlinear regression, the roadway safety factor prediction model is constructed. Actual engineering verification shows the relative error between calculated value and the actual value is 4.4% which means the model has high reliability..It is highly recommended that the safe distance between stope and roadway should be greater than 64.1m(F greater than 1.2) at 1200 m sublevel.(4) Explore pillar progressive failure process on the basis of dynamic strength reduction calculation methods. The result shows that pillar damage appeared from the corners firstly, then gradually to the bottom center and evolved to breakthrough. According to the increasing trend of the number of damage units, the evolution of damaged area can be divided into three processes including stabling, expanding and mutating. The correctness of the analytical result is verified by in-site displacement monitoring result.(5) Considering the influence of external load on pillar stability, construct pillar mechanics analysis model and ensure the safety coefficient(K)of the pillar according to ratio of the ultimate strength and load of pillar. Field engineering analysis shows that in the residual mining stope of line 57~59 on 1420 mlevel, when the pillar reserved width of 8 m and height of 12 m, the stope is in a stable state(K = 1.62). With the pillar height increasing, pillar safety coefficient value decreased correspondingly, and when the pillar height is up to 30 m, K=1.27, which still meets the basic requirements of the mine safety production.