Research On Overburden Activity Law Of Fully Mechanized Mining Of Thick Sandstone Roof Of Medium-thick Coal Seam In Hulusu Coal Mine

At present,the coal mine in Inner Mongolia is basically in the mining stage of shallow coal seam.However,due to the complex geological conditions of coal mines,the depth of coal seams varies greatly.Taking Hujierte mine area in Inner Mongolia as an example,the mining depth of coal seams in this mining area is generally exceed600 m.Therefore,the study of shallow seam mining can not fully guide coal mining in Inner Mongolia.Based on the mining conditions of 21102 fully-mechanized coalface in Hulusu Coal Mine,this paper research on overburden movement law of fully mechanized mining of thick sandstone roof of medium-thickness seam in Hulusu Coal Mine by site investigation,laboratory test,theoretical analysis,numerical simulation and field measurement.The main research results of this paper are as follows:(1)This paper analyzed and summarized the mining geological conditions of Hulusu Coal Mine,carried out the mechanical parameters test of coal and rock mass in 21102 fully-mechanized coalface,The uniaxial compressive strength of 2-1#coal and its immediate roof,basic roof and immediate bottom were measured to be 12.97MPa,17.48 MPa,33.73 MPa and 38.31 MPa,respectively,and the tensile strength was 1.22 MPa,1.89 MPa,4.24 MPa,6.15 MPa,meanwhile the shear strength under different loading angles was also measured.(2)According to the research results of the basic roof beam fracture model and thick plate model,it is concluded that the first weighting interval of 21102fully-mechanized coalface is 51.6 m and 40.6 m,and the periodic weighting interval is 21.1 m and 25.0 m.It was determined that the basic roof of the coalface during the first weighting and the periodic weighting had tensile failure at the center of the long side of the clamped boundary in the goaf,which was caused byσ_x.It is concluded that there are 7 layers of key strata in the overburden of working face,of which the 29th layer is mainly fine-sandstone and is the main key stratum.(3)According to the numerical simulation of overburden movement law in21102 fully-mechanized coalface,the first weighting interval of the coalface is 45 m,the periodic weighting interval is 20 m,and the advance support pressure peak is 40.2MPa,which is about 10 m ahead of the working face.When the working face is advanced to 300 m,the working face is full subsidence.At this time,the maximum subsidence of the basic roof is 2.52 m,the maximum subsidence of the second key stratum is 1.99 m,and the maximum height of the overlying plastic zone is 201.4 m.The height of caving zone is 15.8 m,and the fractured zone height is 49.5 m.The fissure in the goaf has been compacted,a large number of fissures are developed only in the coal face and the upper part of the open-off cut.(4)According to the field measured pressure data,the first weighting interval of21102 fully-mechanized coalface is 41.4 m and the periodic weighting interval is 22.2m.It can be seen that there is no large error between the calculated result of the thick plate model and the measured value,and the numerical simulation result is conform to the measured value,which indicates that the simulation result is relatively ideal.The periodic weighting of the roof changes periodically,about every 1~3 times after the general weighting will occur a intense weighting,and the relationship between the intense roof weighting and the goaf water inrush is analyzed and summarized.(5)According to the on-site drilling into method of 21102 fully-mechanized coalface,the caving zone height is 15.8 m,the fracture zone height is 45.6 m,with the experience formula and Shendong mining area measured height of the“two zones”data fitting formula the caving zone height error was 90.4%,22.5%,the fracture zone height error was 36.1%,15.2%.According to the analysis,the comprehensive analysis on empirical formula is not applicable to this working face,but Shendong mining area measured data fitting formula can provide some reference for the prediction of the height of the“two zones”in the mine.The dissertation contains 57 pieces of figures,17 pieces of tables and 114 pieces of references.