Study On The Law Of Overburden Movement And Surface Subsidence In Strip Mining Of Steeply Inclined Coal Seam

Steeply inclined coal seam refers to a common and complex coal seam with an inclination greater than 45°,Its damage of overburden form,movement mechanism and law of surface subsidence are quite different from horizontal coal seam or gently inclined coal seam.Predecessors have conducted in-depth research on the problems of rock stratum and surface movement in the mining of steep coal seam,but the research on the law of overburden strata movement and surface subsidence in strip mining of steeply inclined coal seams is still not deep enough.Therefore,it is urgent to study the development and evolution laws of mechanical behaviors such as overburden movement and surface movement and deformation in strip mining of steeply inclined coal seam.This paper takes the 1201～1203 working face in the lower west No.2 mining area of Linsheng Coal Mine in Shennan mining area as an example.Based on the actual mining data and field measurement,theoretical analysis is carried out,combined with UDEC and FLAC^3D numerical simulation and indoor physical and mechanical tests,overburden movement law,the failure characteristics and surface subsidence law of the 1201～1203 working face mining are analyzed and studied.The main research contents are as follows:（1）According to the support conditions around the roof of steeply inclined coal seam,different mechanical methods and models are used to analyze the roof movement deformation,failure mechanism and stability;the failure form of the floor and the calculation of displacement in the simplest case of strip mining in steeply inclined coal seam.The mechanical analysis of the coal pillar in strip mining is carried out,the stress characteristics of the coal pillar are analyzed,the stability judgment method and the reasonable reserved size of the coal pillar are obtained.（2）According to the theoretical analysis and field measured data,a variety of strip mining schemes are preliminarily obtained,and the optimal scheme is selected according to the strip mining principle.The surface subsidence prediction is carried out for the optimal mining scheme,results show that the influence of surface subsidence caused by working face 1201～1203 is within the allowable range,and the scheme is reasonable and feasible.（3）Based on the actual situation of strip mining in Linsheng coal mine,the numerical simulation model of strip mining in steeply inclined coal seam is established by using the UDEC software of discrete element numerical simulation.The characteristics of stress,displacement,deformation and failure after strip mining in steeply inclined coal seam is analyzed,and the movement law of overlying strata is preliminarily obtained.Then models under the conditions of different dip angles,different mining thicknesses,different mining sequences of working faces influencing factors are established respectively.Through the calculation results,it is obtained that when the dip angles and mining thicknesses are large,the roof fracture pattern changes in a"V-W-U"shape from top to bottom,and the overburden movement rules are summarized.（4）Based on the actual situation of strip mining in Linsheng coal mine,the surface subsidence law is preliminarily obtained according to the obtained displacement nephogram and prediction curve through FLAC^3D numerical simulation calculation.Compared with the improved Pearson type III function and the measured data,the prediction results are obvious and accurate,the surface subsidence law of strip mining in steeply inclined coal seam of Linsheng coal mine is analyzed comprehensively.The paper has 58 figures,6 tables and 69 references.