| For a long time,coal and gas outburst,gas explosion,mine water inrush,roof caving and other problems seriously threaten the coal mining.With the increase of mining depth,these problems are more serious.The upper and lower through fracture of rock stratum is the passage for water and gas to flow into the working face.The damage and movement of overburden caused by coal mining is the source of mine disasters such as water inrush,roof caving,coal and gas outburst.Therefore,the study of the development law of the height of "two zones" of overburden can provide theoretical basis for the mining technology design of working face,water conservation mining,pressure relief gas migration of adjacent layer,mining of lower protective layer,design of drainage and drilling,gas control,etc.In this paper,the deformation and failure characteristics of the overburden and the development height of the two zones in the fully mechanized coal face of the short distance coal seam are studied.The main conclusions are as follows:1:Based on the investigation and analysis of the mechanical parameters of the overburden roof of Tongting 864 working face,it is concluded that the overburden roof types of Tongting 864 working face are all medium hard roof.It can be seen from the development height data of "two zones" of overburden that the results of development height of "two zones" of overburden determined by various research methods are similar,they are all in the same range,and the research results of mining overburden failure characteristics have good consistency.Comprehensive consideration shows that after the stoping of Tongting 864 working face,the development height of caving zone is 6.86-13.1m,and the development height of fracture zone is 41.31-55.4m.2:Theoretical analysis shows that the influencing factors of the development of "three zones"are:lithology and composite structure of overburden,mining height and layered mining,strike length of working face,mining method and roof management,fault influence,etc.Therefore,the development height of two zones in different positions of Tongting 864 working face will be different.According to the stress characteristics of overburden,overburden is divided into elastic zone and plastic zone from top to bottom Deformation area,tension fracture area,tension failure area and local tension area,elastic area and plastic area are divided into bending subsidence zone,tension fracture area is divided into fracture zone,tension failure area and local tension area are divided into caving zone.3:Through theoretical analysis,the failure characteristics,fracture development and judgment of coal and rock mass are obtained,which provides theoretical basis for the fracture,development and stress change of overlying rock in the mining process.With the advance of mining,the size of fractal dimension is directly determined by the fracture development state,so it can be seen that fractal dimension is a characteristic value reflecting the fracture development state quantitatively.4:Through a variety of research methods,it is obtained that after the stoping of Tongting 864 working face,coal seam 7 is in the middle of the fracture zone.After taking certain safety measures,coal seam 7 can be normally mined,and the influence of coal seam 8 on coal seam 7 is small.At the same time,coal seam 7 is affected by mining,and the pressure relief gas enters into the working face through the mining fracture channel,so it is necessary to strengthen the gas pipe during the mining period of the working face Management work.Figure[53]Table[12]References[76]... |
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