The Study On The Stability Of Goaf And The Recovery Of Residual Pillars For Steeply Inclined Thin Ore Body

The steeply inclined thin ore body which utilize open-stope method stoping left a large number of goaf and residual pillars,to bring a serious security hidden danger of deep mining and residual ore recovery.Therefore,the stability of the goaf needs to have an accurate judgment,in ensuring the economy,reliable and safe under the premise of the remaining pillars for mining,is the old and new mine enterprise need to solve the major technical problems.In this paper,we take the Piao-Tang Tungsten Mine as an engineering example.The means like field investigation,theoretical analysis and numerical simulation are applied to analyzed the stability of goaf.The stability of top pillars and wall pillars mass in goaf has been discriminated,and the feasible,safe and reasonable mining project of the residual pillar is proposed.The main research contents and results are as follows:(1)Based on the investigatio n and sampling,the mechanical parameters of three kinds of rocks were obtained through the laboratory.The generalized Hoek-Brown criterion was used to obtain the mechanical parameters of the rock mass.(2)Based on the ground pressure survey,the causes of ground pressure has been analyzed.The main factors of the ground pressure in the middle and east of the mining area are: the gravity stress field,the structure fracture zone,the special topography,the unbalanced mining,the influence of surrounding goaf,the surface water infiltration in subsidence area.(3)A single goaf of 3-D scanning model by using the laser detector,and the overburden and less than burden of the pillar are obtained.According to the investigation of the goaf and the middle plan,the three-dimensional distribution map of the mined-out area was established.(4)In view of the defects in the process of determining the weight of influence factors,the maximum entropy theory is introduced to construct the multi-objective programming model,which makes the weight distribution more scientific and reasonable.Based on the unique advantages of unascertained measure theory in dealing with uncertainty and concealment,a single goaf stability evaluation system was constructed.And applied to the practical engineering,the stability grade of 52 goaf was obtained.(5)A simplified mechanical model was established for the top pillar and wall pillar in steeply inclined thin ore body.The catastrophic failure model was established by using the cusp catastrophe theory.The control variables a,b and stiffness k of the system are the necessary and sufficient conditions to determine whether the mined-out area is stable and unstable.(6)According to the problem of serious loss and impoverishment in the recovery process of remnant pillars,this paper puts forward the method of upward slicing and cementing filling mining.The critical thickness of the horizontal pillars recovered by the loose waste rock was calculated by using FLAC3 D.Finally,it was determined that the 31132 stope had at least 7 m high insulating pillars to support the upper loose waste rock filling.Through the optimization of the stope structure parameters and mining sequence,the symmetrical mining project with the structural parameters of 4.5×5 m(height×width)is determined.