Research The Breakage Of The Overlying Rock And The Development Of Water-conducting Fissures In Yushuwan 2^-2 Coal

Large-scale and high-intensity mining in the Yushen mining area has a serious impact on the local fragile ecology.Therefore,analyzing the breaking characteristics of overlying strata and the development of water-conducting fissure zones in different mining methods is particularly important for water-preserving mining in the mining area.Based on the geological conditions of the20105 working face of Yushuwan Coal Mine,the thesis systematically analyzes the breaking characteristics of the overburden and the development of water-conducting fissure zone under different mining methods in the 20105 working face using theoretical analysis,physical simulation,numerical simulation and field measurement.The research results are as follows:(1)Physical simulation shows that during upper slicing mining,when the working face advances to 18 m,the direct roof collapses for the first time,and when the working face advances to42 m,the basic roof collapses for the first time;the average stepping distance is 20 m for small cycles and 20 m for large cycles.The average pressure step is 43 m,the development height of waterconducting fissures is 146.6m,and the crack-to-production ratio is 24.43;after the upper layer stoping,the average subsidence of the sub-critical layer is 5.13 m,and the average subsidence of the main key layer is 4.89 m.The average layer subsidence is 2.9m,the development height of the waterconducting fracture zone is 146.6m,and the fracture-production ratio is 24.43.When mining in lower slicing,when the working face advances to 12 m,the roof collapses directly,and when the working face advances to 32 m,the roof breaks and sinks;the average step distance for small cycles is 12.5m,and the average step distance for large cycles is 25 m.The development height of waterconducting fissures is 182.5m,and the fracture-to-production ratio is 15.21;the average subsidence of the sub-critical layer after the lower layer stoping is 11.2m,the average subsidence of the main key layer is 10.8m,and the average subsidence of the red soil layer is 10.2m,The development height of the water-conducting fracture zone is 182.5m,and the fracture-production ratio is 15.21.(2)Numerical simulation shows that when the upper slicing mining is carried out,when the working face advances 36 m,the direct roof collapses for the first time;when the working face advances 110 m,the separated layer cracks develop to 142.8m;the upper slicing mining is completed,and the sub-critical layer sinks The amount is 4.7m,the settlement amount of the main key layer is4.5m,the settlement amount of the laterite layer is 4.3m,the development height of the waterconducting fracture zone is 144 m,and the fracture-to-production ratio is 24.0.In the case of lower slicing mining,when the working face is advanced by 90 m,the subsidence of the sub-critical layer is 7.5m;when the working face is advanced by 130 m,the subsidence of the sub-key layer is 9.1m,and the subsidence of the main key layer is 6.2m;The key stratum was broken and sunk,the waterconducting fissure zone developed to 184.3m in height,and the crack-to-production ratio was 15.36.When the whole layer is mined,after the working face is mined,the maximum subsidence of the sub-key layer is 10.6m,the maximum subsidence of the main key layer is 10.3m,the height of the water-conducting fissure zone is 238.2m,and the crack-to-production ratio is 19.83.(3)The actual height of the "Second Zone" measured by boreholes shows that when mining in layers on the 20105 working face,the development height of the caving zone is 20.60?27.90 m,the caving ratio is 3.43?4.65;the height of the water-conducting fissure zone is 117.80?148.90 m,The ratio of cracking to mining is 19.63?24.82.The measured results are basically consistent with the physical simulation and numerical simulation results.(4)The change law of the borehole water level in the phreatic aquifer of the Sarawusu Formation shows that the development height of the water-conducting fissure zone of the overlying rock in the layered mining of the 2-2 coal seam reaches the middle and lower part of the red soil water-proof layer,and does not penetrate the red soil water-proof layer.It is believed that layered mining has limited impact on the aquifer of the phreatic aquifer in the Sarawusu Formation,which further verifies that the mining method of layered mining is scientific and reasonable.