Study On The Prevention Method Of Rock Burst By Protection Pressure Relief In The Nearly Vertical And Extremely Thick Coal Seams

In order to effectively prevent and control the pressure bumping during the mining of nearly vertical and extremely thick coal seam group,the south mining area of Wudong coal mine in Urumqi mining area was taken as the study objective,the rock burst problem of nearly vertical and extremely thick coal seam group was studied by using the methods of theoretical analysis and numerical simulation.The main research contents and main conclusions of the thesis are as listed as follows:1.This paper analyzed the influencing factors of rock burst in nearly vertical and extremely thick coal seams in Wudong coal mine from two aspects---geological factors and mining technology factors.The geological structure,hard roof and floor rocks,coal and rock impact tendency,and the roadway layout are the main factors,which obviously affect the rock burst of the nearly vertical and extremely thick coal seams in the southern mining area of Wudong coal mine.2.Based on the previous rock burst events in the southern mining area of Wudong coal mine,the reasons were analyzed to explain the rock bursts occurred in the nearly vertical and extremely thick coal seams in the southern mining area of Wudong coal mine.During the mining stage,the coal is under the combined action of the supporting pressure and the horizontal tectonic stress,that induced by the bending of the roof and floor,respectively.In consequence,the coal in excavation is in a state of "high static load",thereby accumulating a large amount of elastic energy.Once the state of coal was disturbed by mining and roof activities,which is easy to induce rock bursts.Numerical analysis method was used to simulate the mining processes of + 425 m stage of B3+6and B1+2 coal seams,and the stress distribution characteristics of surrounding rock.As a result,there are two high stress concentration areas under the mining stage of B3+6and B1+2 coal seams,and the mining face is located in the high stress area,that is the reason of the high potentional of impact risk existed in the mining process.3.The mining of the protective layer can play a role of reliefing certain pressure,thereby protecting the protected layer,which reduce the impact risk during the mining of protected layer.Different mining schemes for B3+6 coal seam and B1+2 coal seam were designed.Numerical simulation was applied to obtain the stress distribution and plastic zone distribution of coal and rock mass under different mining schemes.Comparing the simulation results of different mining schemes,and the protection layer was optimized.The protective layer and the protected layer were determined,and the mining sequence of the B3+6 coal seam and the B1+2 coal seam at a depth of 425 m and below was determined.4.Considering a high risk of impact that still existed in the process of mining the nearly vertical coal seams,a method of pressure relief and anti-impact was proposed to design a self-protection layer in the first mining coal seam.Through pre-cracking in the coal of a certain thickness at the mining stage,and setting up a self-protection layer,the stress field of the coal and rock mass was changed,exhibiting transfering the high-stress areas to the deep part of the coal-rock mass,and releasing the stress in the mining face.In addtition,this method can also change the nature of the coal and rock mass,which reduce the possibility of accumulating the amount of elastic energy,thereby preventing the occurrence of rock burst.The research results of this paper can provide a certain basis for the study of coal mining methods and processes in near-upright and extra-thick coal seams,and provide a new idea and method for preventing and controlling rock bursts in such coal seams.The paper has 48 pictures,16 tables,and 86 references.