| The Shendong mining area is located in the core area of energy "golden Triangle",where the coal resources are extremely rich.the favorable coal seam occurrence condition impels the Shendong mining area priority to realize the large-scale modernized mining of coal resources.Compared with traditional mining technology,modern mining technology has the characteristics of large area and fast speed of one mining face,coupled with the characteristics of the special overburden assemblage types in the Shendong mining area,which leads more violent impact on overburden failure by mining,brings serious harm to the safety production and ecological environment of the coal mines in Shendong mining area and brings many technical problems to pressing coal mining.Although most of the mines in Shendong mining area have broken through difficulties in mining tens of millions of tons of annual.But the Bulianta coal mine as the representative of tens of thousands of tons of mines realized large-scale and efficient mining,meanwhile faced the safety of mining,environment restoration of mining area and other problems.The severe damage caused by high strength mining is a serious threat to the safety of mine water prevention and surface constructions.The most representative 12551 working face of the Bulianta coal mine realized mining full-height of 8m extra thick seam in the fully mechanized mining,which leads the violent movement of the overlying strata on the working face,results in large deformation of the surface,and forms water guide channel with good connectedness,In addition to the perennial flow Wulan Mulun is located in the east of the well,which forming the good water filling conditions for the bringing great security risks for safety production of 12511 working face of Bulianta coal mine.Therefore,it is instructive to study the failure law of 12511 working overburden Rock in the coal mine.Based on the study of the 12511 working face of the connecting tower,this paper analyses the development,settlement change and stress change of the overlying strata by simulating experiments with similar materials and UDEC numerical simulation experiments.Secondly,the development height of "two belts" in the working face is analyzed by using the leakage observation of drilling fluid and the color TV observation The main conclusions are as follows:(1)The calculation formula of the initial and periodic caving distance of roof is deduced,it is used to calculate the roof caving in the 12511 working face of the connecting tower coal mine,the first caving step distance is 28.4m,the period caving step distance is 11.6m,and the model is calculated by numerical simulation to calculate the first roof caving step distance is 30 m,The cycle caving step distance is 15 m.The results are in good consistency.(2)According to similar simulation,fracture development is divided into open cut eye-roof initial pressure,roof first to pressure to cycle,face and cut near three stages.The subsidence process of overburden rock is non-linear;The higher the overlying strata is,the more closely the stress state of the original rock is,the lower the caving zone is.The height of the model is 45 m,and the fracture zone is 117 m.(3)The caving ratio and crack-mining ratio are higher than that of thick seam in fully mechanized mining of extra thick seam.The ratio of caving ratio and splitting ratio is higher than the ratio of mining height,and it can be concluded that the influence of seam thickness on the height of water conduction fissure is greater than that of caving zone.At the same time,the fully mechanized mining in extra thick coal seam has a greater influence on mining,and it takes longer to stabilize.But the transfer process of overburden subsidence is not affected by mining height.There is no obvious difference in the overburden stress change process between the fully mechanized mining in the extra thick coal seam and the thick coal seam,but the maximum stress level is 11.6 higher than the thick seam fully mechanized mining.(4)Using the method of combining the leakage observation of the drilling fluid and the color borehole TV observation,the ratio of the 4.61~5.12 of the 12511 working face of the filling tower coal mine is measured between the 13.92~16.37 and the splitmining ratio.The two bands "distributed in accordance with the" saddle "type of overburden rock failure pattern.From the angle of overburden stress,subsidence and damage range,the similarity simulation,numerical simulation and field measured results are compared and analyzed,which proves the credibility of the research conclusion.The difference between the development height of the "two belts" and the overall law of Shendong mining area is obtained by comparison and analysis. |
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