Study On Overburden Damage Movement Law Of E3₂13 Working Face In Qianyingzi Coal Mine

The mining area of thin bedrock coal seam in China is wide and the output is huge.However,the frequent occurrence of water inrush accidents caused by water rock coupling not only causes huge economic losses,but also damages the groundwater environment and causes serious social harmness.E3₂13 working face is the first working face with sand proof pillar in Qianyingzi coal mine.If no engineering measures are taken,there is the possibility of water inrush and sand burst.Therefore,it is necessary to analyze the overburden structure of E3₂13 working face and study the development law of failure movement.On the basis of consulting the latest research results of overburden failure movement evolution law at home and abroad,combined with the overburden structure characteristics of E3₂13 working face in Qianyingzi coal mine,transient electromagnetic and radio wave penetration were designed and implemented to explore the water abundance,shape and influence range of overlying rock and DF2 fault structure in E3₂13 working face;Two post mining "two belts" height detection holes were constructed by means of flushing fluid consumption and borehole television after mining.On this basis,based on the seepage and strata control of the mining rock mass,the mechanical parameters of the core of the "two belts" height exploration drilling are tested through the indoor uniaxial tensile and compressive strength test.According to the test results,the mining evolution analysis model is constructed,and the dynamic evolution characteristics of the overlying strata after mining are displayed by using FLAC3 D software,The research results are as follows:(1)In E3₂13 working face of Qianyingzi coal mine,the length of machine roadway is1154 m,the length of air roadway is 1132 m,the width of open-off cut is 301 m,the roof elevation of the highest point of the working face is-221.697 m,the elevation of the overlying bedrock surface is-153.8m ^-156.5m,the average coal thickness is 3.3m,the average dip angle is 11 ° and the comprehensive mechanized mining method is adopted to manage the roof.(2)A total of 273 transient electromagnetic detection points are designed and installed,with a total engineering quantity of 2700 m.There are 70 transmitting points and242 receiving points in the radio wave penetration pit.The length of side line is 2400 m,and the perspective distance is 350 m.One water rich abnormal area is detected by transient electromagnetic detection,and eight abnormal areas are detected by radio wave penetration pit.For the abnormal area,13 exploration and verification boreholes are designed and constructed in E3₂13 lane,The total engineering quantity is 907m.Two boreholes are designed at the upper opening of the open-off cut in the inner section to explore the characteristics of overburden rock combination and the thickness and water rich property of"fourth aquifers",with a total engineering quantity of 265m.Three boreholes are designed at the front open-off cut of the inner section to explore the characteristics of overburden rock combination and the thickness and water rich property of"fourth aquifers",with a total engineering quantity of 600m.The bedrock surface elevation corresponding to the highest point is-155.6m after drilling verification.(3)The thickness of the third aquifuge near E3₂13 working face is 24.15m?78.00m,with an average of 44.44m.The occurrence of the third aquifuge is stable,and the"fourth aquifers"are relatively flat,with a thickness of 0m?9.45m,with an average of2.06m,sporadically developed,and mainly distributed in the west side of the working face.The unit water inflow q=0.00066L/(s·m)?0.0014L/(s·m)and permeability coefficient K=0.00043m/d?0.014578m/d of"fourth aquifers"indicate that the water yield of"fourth aquifers"is weak,and the mining grade of water body classified according to mining standard is class II,and sand proof coal pillar can be reserved in E3₂13 working face for mining.(4)According to the data of"two belts"height detection hole after mining,the roof of coal seam is mainly composed of mudstone,sandy mudstone and siltstone.Mudstone,siltstone and other overburden with good water barrier performance account for a relatively high proportion.The content of mudstone in the"fourth aquifers"exploration borehole accounts for more than 80%,The content of mudstone accounts for more than 90%in"two belts"high hole exploration,the rock mechanics test results show that the uniaxial compressive strength is 6.66Mpa?45.3Mpa,and The overburden structure consists of soft rock and medium hard rock.According to the mining specification,the mining height is4.0m The height of the safety coal and rock pillar for sand control is 45.6m,which is less than the actual 66m.It meets the requirements of the code for coal pillar setting and coal pressure mining in buildings,water bodies,railways and main roadways.The E3₂13working face is provided with safe mining conditions.(5)According to the post mining"two belts"height hole drilling histogram,indoor uniaxial test on the rock core sampling test to obtain the lithologic mechanical parameters,the numerical model of E3₂13 working face is constructed,and the application of the FLAC^3Dcomputer numerical simulation makes computer numerical simulation analysis on displacement,strain and plastic change of working face roof mining,and obtains that under the numerical simulation,the development height of overburden caving zone is 10.9m,and the development height of water flowing fracture zone is 42m.(6)According to the characteristics of high development degree of caving zone and water flowing fractured zone during the period of periodic weighting after mining,two"two belts"height detection holes L1 and L2 are designed and constructed in the shallow part of the working face.By means of drilling flushing fluid consumption,water level observation,drilling television,sticking,dropping and air suction,the height of caving zone is measured to be 10.68m?11.98m and the height of water flowing is measured to be10.68m?11.98m The height of water fissure zone is 40.86m?44.98m,the collapse mining ratio is 2.97?3.33,and the fracture mining ratio is 11.35?12.49,which is close to the results of code calculation and numerical analysis,and can be used as the basis for coal pillar setting and safety evaluation of similar working face.(7)When the paper is completed,the E3₂13 working face has been safely mined426m,and no water burst and sand break safety accidents have occurred.The water inflow of the working face is 5m³?15m³,which indicates that the geophysical prospecting prediction,drilling exploration verification,laboratory analysis and test of rock mechanics performance,numerical simulation of the failure evolution law of overburden,and the mutually verified evolution rules of overburden failure movement verified by the development height of the"two belts"high hole after mining The law research idea is feasible,and the conclusion that E3₂13 face has safe mining conditions is reliable.Figure[29]Table[18]Reference[91]...