Study On Temporal And Spatial Characteristics Of Overburden Migration And Surface Subsidence In Shallow Coal Seam Under N00 Mining Method

For a long time,coal plays a leading role in China’s energy system and has made indelible contributions to China’s economic development.Coal is a non renewable energy,and its reserves are extremely limited.With the continuous extraction of underground resources,its reserves are becoming less and less.The problem of resource waste caused by the traditional coal pillar mining technology is becoming increasingly prominent.In order to solve this problem,the roof cutting and pressure relief non pillar mining technology was bred.This technology is not only in line with the important development direction of sustainable mining of coal resources,but also to solve the problems of gas and power disasters in coal mines It is an important guarantee to reduce the tunneling rate of roadway engineering and realize scientific mining.However,according to the current research at home and abroad,the optimization of roof structure by roof cutting and pressure relief pillar free mining makes the law of overburden rock movement and surface subsidence very different from the traditional mining method.Therefore,this paper takes the N00 construction method test face of shallow coal seam in Shenfu mining area as the research basis,and comprehensively uses the research methods of theoretical analysis,microseismic monitoring,surface observation and so on,The temporal and spatial characteristics of overburden rock movement and surface subsidence in roof cutting and pressure relief non pillar mining are studied.The research results can provide a certain reference value for the prediction of surface subsidence and the green mining of coal under the pressure relief and pillar free mining of shallow coal seams.The main research results are as follows:(1)Based on the structural characteristics of self forming roadways without coal pillars,the "deformation structure"and "stable structure" of roof strata under N00 construction method are studied,and the asymmetry of ground pressure behavior is analyzed.Combined with the laws of overburden fracture and fracture development under N00 construction method,the relationship model between overburden fracture and surface subsidence with space-time characteristics is established,which provides a theoretical basis for the prevention and control of surface subsidence under N00 construction method.(2)Using ESG high-precision microseismic monitoring system,the temporal and spatial evolution law of microseismic events and the law of overburden fracture and migration are studied.This paper summarizes the distribution characteristics of microseismic events in time and space during N00 working method mining in Ningtiaota S12012 working face,and describes the overburden fracture layer with the number,distribution range and energy release of microseismic events.According to the microseismic events,the height of the collapse zone of working face S12012 is 38.25m,the height of the fracture zone is 91.24m,and the average pressure step distance is about 21.25m.The basic roof shows "U+Y" fracture under N00 construction method.The sub key layer is broken after 65.8m of mining,and the main key layer is broken after 135m of mining.(3)By setting up surface observation stations to monitor the characteristic parameters of surface subsidence,subsidence speed,horizontal displacement,surface cracks and so on under N00 construction method,the characteristics of surface deformation in the initial weak stage,development sudden increase stage and stable decline stage are summarized.The relationship between overburden fracture and surface cracks is analyzed,and the temporal and spatial characteristics of overburden movement and surface subsidence in the process of mining are explored.(4)The existing surrounding rock control scheme of S12012 working face in Ningtiaota Coal Mine is optimized,which provides a new idea for the surrounding rock control of N00 method and the selection of roadway support structure.After the field implementation,the stability of the surrounding rock roadway in the mining process is improved,which provides a guarantee for the safe and efficient mining of the working face.