Roof Strata Rupture Regulation And Surrounding Rock Control In Single Pass Longwall Mining With Cutting Height Of 8.8m

China's rapid economic and social development is inseparable from energy supply,coal as an important support of China's energy supply,play a decisive role.China has a vast wealth of resources and huge coal reserves,especially in Shenfu Dongsheng coal field and Xinjiang coal field.Shenfu Dongsheng coal has mature development,stable production capacity and good coal seam occurrence conditions,making it the final production area for coal supply in China.With the continuous development of coal mining equipment and technology,China's coal mining equipment and technology has reached the world's leading level.The production of 8.8m fully mechanized working face represents the highest level of coal mining in China.Due to the complexity and diversity of the mining of the 8.8m extra-thick coal seam,such as thin coal seam,medium thick coal seam and thick coal seam.The following technical problems still exist in the mining process,which need to be solved urgently :(1)large underground space in the stope,increasing difficulty in roof control,and large safety risks of roof caving after working face pressure;(2)The failure and instability mechanism of surrounding rock is not clear,and the process of overburden movement,the failure mechanism of high-sided coal wall and the surrounding rock control principle need to be further studied.(3)The dynamic evolution process of strata movement and mining stress in the mining process has not been mastered;(4)A complete set of practical and feasible surrounding rock control method for super-high stope is not proposed.(1)Through field observation and analysis of a large stope with a height of 8.8m,it is obtained that the initial pressure stepping distance of the working face is 45 m and the average cycle pressure stepping distance is 12.1m.Under the influence of mining,the development characteristics of overburden rock are as follows: the height of caving zone is 48 m,5.45 times that of mining height;the height of fracture zone is 108 m,12.27 times that of mining height.During the advance of working face,only caving zone and fracture zone exist in the overburden rock where the bedrock is relatively thin.For each 80?100m advance of the working face,relatively large cracks will appear on the surface,and the width of cracks near the two channel slots becomes narrower.The upper and lower channel of the corresponding working face on the surface is the step crack,the width of which is generally no more than 20 cm,and the step drop is no more than 30 cm.(2)The structural mechanics model of the roof of large stope with high stope was established,and the conditions of roof sliding and revolving instability were found to be related to the size of roof control distance.When the roof control distance was large,free-falling instability would occur;otherwise,gyroscopic instability would occur.In view of the two instability modes,a method for determining the dynamic load impact force of roof under different instability modes is proposed.Zy26000/40/88 d hydraulic support is developed to realize the stability control of roof of large stope.Through the shallow buried coal seam high wall failure mechanism for coal and coal wall stability analysis,constructed considering support care for structural mechanics model for analyzing the stability of the coal wall,when the high part of shallow buried mining coal wall while the tensile stress appears in its value increased with the increase of coal wall height increase.Ultimately brittle tensile failure of coal wall,explains the 8.8 m large mining height are broken stope of fully mechanized working face of coal wall type casting damage mechanism.(3)The model test reveals the characteristics of overburden movement,strata movement and surface subsidence during the advance of the fully mechanized top-face with a large mining height of 8.8m.In the mining process of the simulated working face,the initial pressure step distance of the basic roof is 54 m,the periodic pressure step distance is 13-30 m,and the initial rupture distance of the main key layer is79 m.Numerical simulation model is established,and reveals the stope stress distribution and evolution characteristics,strata movement characteristics,rock caving features,surface subsidence,etc.,the study found that as the working face advancing,maximum and minimum principal stress in the coal seam ahead of mining face are stress concentration phenomenon occurs.The stress concentration degree increased with the increase of working face advancing range increases,the strata movement and surface subsidence with evolution characteristics of face advance.(4)according to the different buckling modes of roof dynamic load,and a method for determining the impact of roof pressure was calculated,it is concluded that the working face in about 10% of the stent with crushing during risk,proposed the 8.8 m large mining height mine pressure prediction method and the stability of surrounding rock control method,and USES the governance effect of 3D laser measurement system of coal wall were measured,the results show that governance after the coal wall damage fracture significantly reduced,coal wall stability improved.