Study On Rockburst Prevention And Control Technology In Working Face Mining Under Coal Pillar In Goaf

A large number of studies show that in multi-coal mining,the upper protective layer should be mined first.However,in the actual mining process,some coal pillars are left in the overlying coal seam due to faults,coal thickness change,mining layout and other factors,which often becomes a stress concentration area,increasing the risk of the lower coal seam and affecting the safe production of coal mine.The 8332 working face is located under the 7235 and 7332 goafs,and the static load stress of the remnant pillar between the two goafs is high.Under the influence of mining in the working face,it is easy to induce rock burst.Therefore,this paper takes the 8332 working face that under the coal pillars in the goaf of Xuzhuang Coal Mine as the research object,combined with the actual mining situation,analyzes the impact factors of the working face and the evolution law of overburden structure.Through the numerical simulation method,the stress distribution characteristics of surrounding rock at various mining periods of the working face were analyzed,and the spatial-temporal evolution law of the microseism and the rupture mode of the seismic source during the mining of the working face were combined with the microseismic data.,finally puts forward the impact of 8332 face dangerous monitoring,prevention and control technology and applied to the field,the following conclusions:(1)Combined with the actual situation,by analyzing the impact risk factors of the working face and the evolution law of the overburden structure,it is concluded that the mining of coal pillars and protective layers in the goaf is the main reason for the mining shock risk of the 8332 working face;In the early mining period of the 8332 working face,the "F" space structure was formed again in the overly stable overburden structure;in the late mining period,the "T" space structure was formed in the area of the remaining coal pillars.(2)In order to characterize the stress distribution during the mining of the working face under coal pillar in the goaf,a survey line is arranged along the roof of the working face in the direction of the remaining coal pillars and in the direction of the working face.It is found that due to the influence of the upper protective layer,advance abutment pressure in front of the coal wall is generally low,and the stress peak generally appears in the range of 10 ～ 15 m.Only in the first step of mining,advance abutment pressure in front of the coal wall is significantly higher than other mining stages,indicating that the first mining of the working face plays an important role in the safe production;When both sides of the upper protective layer are mined out,advance abutment pressure in coal pillar is 70 MPa on average,and the pressure is higher.In addition to the effect of mining on the 8332 working face,the stress in the coal pillar area of 100 m ahead of the working face will be superimposed again.Up to 79 MPa.Therefore,the risk of the remnant pillar in the goaf is higher.(3)based on the microseismic data,the evolution law of microseismic activities and the source rupture mode were analyzed.It found that the energy and frequency of microseismic are relatively low on the whole,showing a trend of increasing and then decreasing,and then increasing.The microseisms are distributed in an elliptical shape and extend to both sides along the remnant pillar,indicating that the working face has a greater risk of impact during the period from mining to "square" and during the normal propulsion stage;with the mining of the working face,the remnant pillar location changes accordingly.The working face is affected by the remnant pillar in different ways,and the source rupture mode will also change.(4)According to the impact characteristics of the working face under the remnant pillar in the goaf,the rock burst pressure monitoring and prevention technology for the 8332 working face was formulated.Through inspection,it is found that the mine pressure is relatively stable,there is no microseismic activity with an energy greater than 104 J,and the actual risk is low.The research results of this paper can effectively guide the production safety of 8332 working face,and also provide certain theoretical support and technical guidance for the working face mining under similar conditions.The thesis has 62 figures,13 tables,100 references.