| Roof water hazard in coal seam mining is one of the main threats to the safety production of all mines in Binchang mining area,Shaanxi Province,and the development height of the water-conducting fracture zone has a decisive impact on the prevention and control of roof water hazard.In view of the fact that the development characteristics of the water-conducting fracture zone in the fully mechanized caving mining in the Binchang mining area are unclear,this paper takes the 41 panel area of the Wenjiapo coal mine in the Binchang mining area as the research,area,and the 4105 fully mechanized caving face as the research object to carry out different mining height conditions of the coal seam.The research on the failure of the underlying rock and the development characteristics of the water-conducting fracture zone has important theoretical and practical significance for predicting the height of the water-conducting fracture zone in the fully mechanized caving face.Based on the existing geological data,the spatial assemblage relationship of the overlying rocks in the study area is summarized,which are divided into two categories:loess overburden and bedrock outcropping.On this basis,the overburden strata structure of the 4105 working face is judged by using the key layer theory,and it is determined that there are 5 sub-key layers and one main key layer in the overlying strata of the 4th coal.Through the mine pressure monitoring and analysis,the periodic pressure law of 4105 working face is analyzed.The initial pressure step distance of the direct top is 23.70m,the basic top pressure first time pressure step distance is 52.05m,and the basic top cycle time pressure average step distance is 29.34m.The rupture of the upper key layer leads to the early rupture of the lower sub-key layer,which causes the mineral pressure to show significant periodic pressure.The average small pressure appears twice in a row,and a large pressure appears once.The large cycle pressure step is about 50m.,the small cycle to press the step distance is about 20m.Through numerical simulation and theoretical prediction method,the development law of water-conducting fractured zone height was studied under the conditions of mining heights of 7.5,8.5,9.5 and 10 m for 4 coals.According to the numerical simulation results,with the advancement of the numerical simulation working face,the height of the water-conducting fracture zone under different mining heights generally develops in a step-like manner with the progress of the mining.Comprehensive analysis of the results of numerical simulation and theoretical prediction methods,4.The development height of the water-conducting fracture zone in coal mining is controlled by the key layer of the overlying rock.relationship.The research results are verified by the "two-zone" drilling exploration results.According to the stepped development law of the water-conducting fracture zone,the height variation of the water-conducting fracture zone on the strike section of the 4105 working face is analyzed.Using the traditional fracture-mining ratio method and the stepped development method of the water-conducting fractured zone in this paper,the development height of the water-conducting fractured zone in Wenjiapo 41 Panel 4 coal mining is predicted,and whether it leads to the main water-filled aquifers of the Luohe Formation is predicted.Hazards are zoned.The results of the two types of risk zoning are verified by the change of the water level of the Luohe Formation aquifer.The results show that the stepped development of the water-conducting fractured zone is more realistic,and the structure of the key layers in the region does not change the development height of the water-conducting fractured zone.Under the circumstance,the mining height of the coal seam can be reasonably increased through the step-by-step development of the water-conducting fracture zone,so as to improve the coal recovery rate. |
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