| In the process of coal safety production,water accidents of roof and floor have brought huge economic losses and casualties to coal mines.In order to prevent the occurrence of such disasters,it has become an important prerequisite to study the failure characteristics of roof and floor by using relevant testing techniques and methods.The upper working face of Group A coal 13121 in Gubei Coal Mine in Huainan is layered mining on the thin bedrok working face under the thick loose layer.At the same time,it is faced with the threat of water damage on the roof and floor.It is of great significance for safe mining of the working face to master the development law of rock failure on the roof and floor.During the field measurement,two boreholes were arranged on the roof of the upper working face on 13121,and one borehole was arranged on the bottom of the upper working face on 13121.Integrated electrical and optical fiber detection showed that with the gradual advancement of the working face,the physical characteristics of the roof and floor rocks Significant changes have taken place from the background value to the mining impact.According to the resistivity value,current ratio and strain characteristics,it is reflected that the height of the collapse zone is 14m,the height of the crack zone is 34m,and the floor failure depth is 21m.The corresponding caving ratio of the roof rock layer is 3.26,and the cracking ratio is 7.91.Compared with the medium-hard roof,the crack-to-production ratio is relatively small.It is believed that under the condition of thin bedrock,the sandy mudstone near the weathered zone and the argillaceous components in the sandstone contribute to the closure of the fissures and reduce the development of the fissure zone.height.The maximum depth of floor failure is located at the 1 ash top interface,which is equivalent to the floor failure depth of normal coal seam mining.It reflects that the bottom coal seam has little effect on the floor failure depth during upper-slice coal mining,and the floor failure depth is related to the control of the strata structure.The roof and floor borehole data joint inversion method is used to investigate the changes in the physical properties of the roof and floor rocks during the coal mining process of the Group A coal in the 13121 upper face of Gubei Mine.The results show that the resistivity changes between the two holes can reflect the mining process during the mining process.However,it is not intuitive to reflect the comprehensive morphology of the water-conducting fracture zone and the failure zone,which may be related to the repulsion of the relatively high-resistivity coal seam to the current field in the roof and floor range.Through the borehole electrical method and the optical fiber comprehensive geophysical method,the roof and floor rock formation failure rules are comprehensively analyzed.It is judged that the development height of the water-conducting fissure zone in the upper working face of 13121 is 34m,the development height of the caving zone is 14m,and the floor failure depth is 21 m..These can provide certain technical guidance for better research on the failure laws and characteristics of the roof and floor rocks in Group A coal mining.Figure[17]Table[5]Reference[84]... |
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