Study On The Prevention And Prediction Of Surrounding Rock Caving Hazard In The2#Goaf Dongshenmiao Mine

Due to historical mining,Dongshengmiao mine forms dozens of different size andshape goaf,and these goafs have serious effect on safe production of mining.In the Eastmine,according to the statistic of geological department,the scale of2#goaf is larger;thetotal exposuring area of hanging wall and roof is about92968m2;the volume of goaf isabout1101540m3.In the goaf of such large scale,once the hanging wall and roof cave inlarge area,they compress air.The air comes into production roadway from goaf and formsair shock wave in the speed of hundreds of meters per second,and fallng rcok has adynamic impact on goaf bottom structure.Having high pressure,the air shock wave causesserious damage to the underground person and equipment,and is a potential significantsecurity risk of mine safety production.In view of hidden safety problems of goaf,thispaper studies prediction of goaf surrounding rock fall hazard and its prevention and controlmeasures in detail.In order to study safety problems of goaf,this paper mainly adopts Hertzelastic-plastic contact theory，energy conservation principle，theoretical modeling(roofcaving-air coupled impact mechanics model) and MATALAB differentialcalculation.Research results are as follows：(1) The big goaf caving excites air shock wave of38m/s,and its pressure is about4.6MPa;the shock wave jumps into the roadway in the maximumvelocity of523m/s;andthe shock wave has an effect on distance of7812m in the tunnel.This paper simplies fallingblock as a sphere of6.4m diameter,and the falling block hits the bottom structure in thespeed of31m/s.This paper finally obtain the maximum impact force of4.34×109N and themaximum stress of9176397Pa in the bottom structure;the structure damage happenes.(2) Be based on the shock tube test and air flow theory in the porous media,this papercomprehensively calculates the cushion thickness of18m and modifies cushion thicknessformula by introducing a comprehensive influence factor-K.(3) Based on Hertz elastic-plastic contact theory and cushion stress diffusion theory,this paper calculates cushion thickness of10m by punching strength criterion of freebeam.(4) Based on the wave disaster,wave blocking wall arranged in the roadway is lessthan20m between the production area and goaf,thickness of concrete wall is2.7m andeffectively blocks the shock wave.(5) In order to prevent shock wave disaster,the mine opens a skylight well of4.0×4.0m on the top of empty area,and the height of skylight is about208m.(6) In view of the surface subsidence hazard,this paper develop comprehensivemeasures of prevention disaster,such as fencing,cut-off ditch,water retaining wall etc.