| In recent years,with the depletion of shallow coal resources in China,the depth of coal mining is increasing,especially in Juye Coalfield in Southwest Shandong Province.Most of them have the characteristics of large buried depth,huge thick loose layer and thin bedrock.In the process of coal mining,the ground pressure appears violently,the overlying rock movement law is complex,the separation layer and fracture development are irregular,the subsidence law and the conventional coal seam occurrence conditions are displayed There is a big difference in mining.At present,the movement and deformation of overburden rock and the evolution law of separated layer cracks in thick loose layer and thin bedrock mining have become one of the research hotspots in the industry at home and abroad.Based on the engineering background of the first 1302 working face mining in Guotun coal mine in the north central Juye coalfield,the comprehensive research methods of theoretical analysis,similar material simulation test and numerical simulation are used to study the characteristics of overburden fracture and collapse,development of water flowing fracture zone,movement and deformation of overlying rock and evolution law of separated layer fracture The correctness of theoretical analysis and simulation test of similar materials is verified.The main research results are as follows:(1)Through the simulation test of similar materials,it is found that when the excavation reaches 110cm,the fourth strong surface of separation layer breaks and the overlying strata collapse and sink on a large scale.It is inferred that the strong surface of separation layer is the key layer,which controls the movement state of the overlying strata and undertakes the load of 423.36kpa To form a stable and strong bearing structure.(2)Based on fractal geometry theory and simulation test results of similar materials,the evolution law and fractal characteristics of fracture network in overlying strata of goaf are analyzed.The results show that the evolution process of fractures under different mining degrees mainly includes three stages:generation,expansion and compaction.According to the distribution of fractures in overburden,the fracture field can be divided into new fracture area,old fracture area and compaction area;the dimension increasing process of overlying rock fracture network can be divided into three stages,including the early stage and the middle stage of mining The fractal dimension of fractal dimension increased sharply twice,and increased slowly in the later period.(3)Under the mining of thick loose layer and thin bedrock,the development of separation layer and fracture has good self similarity,and its fractal characteristics can better reflect the space occupation situation and two-dimensional space characteristics,and then can reflect the development of overlying rock fissures under the influence of mining and the size and distribution of prototype overburden separation layer.(4)The results show that the average development height of caving zone in 1302 working face of Guotun coal mine is 10.41m,which is about 3.5 times of mining height.The average development height of fracture zone is 69.91m,and the average water flowing fracture zone is 80.31m.The development height of water flowing fracture zone is far greater than the thickness of coal seam roof,which runs through the bedrock aquifer,but does not develop to the aquifer at the bottom of loose layer.It shows that the overlying bedrock aquifer of 1302 working face is more likely to lead into the working face through the fracture zone during the mining process.Figure 54 table 10 reference 80... |
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