| Group A of Huainan mining area(the upper layer is 3 coal,the lower layer is 1 coal)has abundant reserves and good coal types,and is called the "new granary" of the Huainan mining area.However,the mining of Group A coal faces the threat of multiple disasters such as water inrush from the floor,spontaneous combustion of the coal seam,gas,complex roof and soft coal.In order to solve the problem of safe and efficient mining in the lower slicing face of Group A coal in Huainan mining area,the paper takes Group A coal of Pan two Mine in Huainan mining area as the engineering background.The thesis uses the comprehensive research methods of theoretical analysis,numerical simulation,similarity simulation test and field measurement to analyze the characteristics of overlying rock migration under the influence of repeated mining.The paper compares and analyzes the changes of stress environment and the failure characteristics of the roof and floor after the upper and lower stratified working faces are mined.It also calculates and analyzes the working resistance of the working face supports,and selects a suitable hydraulic support.In addition,the paper studies the influence of mining and support parameters such as roof compaction time,working face staggering distance,mining height,support strength and side protection strength on the surrounding rock deformation of the lower slicing fully mechanized mining face.According to the compaction state of the roof and the change of the stress environment,the paper determines the distance of the roadway stagger.The research results of the thesis play an important role in guiding the safe mining of the lower coal face of Group A in Huainan mining area.The main results of the research are as follows:(1)Through similar simulation tests,the temporal and spatial regularity of overburden failure and the development characteristics of "two zones" are obtained.After the lower layer stop,the overlying rock collapse is an asymmetric "?" shape;the initial collapse step distance is reduced by 48%,and the periodic collapse step distance is reduced by 23%,the collapse zone increased by 63%,the fracture zone increased by 13%,the caving angle on the side of the cut-off cut increased by 3°,and the collapse angle on the side of the stop line increased by 9°,and the damage range of the overlying rock formation became larger.(2)Through the establishment of a numerical model,the thesis obtained the stress change law and the failure characteristics of the plastic zone under the condition of different staggered distances.If the lower layer working face is arranged in an internal staggered way,the roof plastic zone will show a "parabola" shape.If it is arranged in an external staggered way,the roof plastic zone will continue to assume a"saddle" shape.Finally,it is determined that the air lanes in the lower layer working face are staggered inward by 30m,and the machine lanes are staggered inward by 10m.(3)The method of numerical calculation is used to determine that the reasonable support strength of the lower stratified working face support should be greater than or equal to 0.8MPa,the mining height should be 3.5m,the strength of the side guards should be greater than or equal to 0.3MPa,and the roof compaction time should be more than 5 years.(4)Based on the structural theory model,the support strength of the lower layer working face is determined to be 0.86MPa.The ZZ7200/18/38d four-column hinged roof beam supporting and shielding hydraulic support was determined to be selected.(5)In order to prevent roof fall and coal wall falling off,the paper puts forward the main measures such as "three machines" model supporting,laying metal mesh to protect the roof of the working face,and grouting reinforcement to the broken surrounding rock.The results of the field application show that the roof control effect of the working face is obvious,the roof coal wall does not fall off,and the roof pressure is relatively relaxed.Figure [65] Table [19] Reference [93]... |
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