Study On Overburden Movement Mechanism And Laws Of Surface Subsidence In Wall Mining Of Steep Coal Seam

Overburden movement is a complex process due to coal mining, the dipangle of steep coal seam is greater than45°, it is precisely because large angleand complex geological structure that it is more complicated that overburdenmovement and surface subsidence due to steep coal seam mining. After coalseam mining, except roof deformation, seam floor would be damaged when coalseam reaches a certain angle; for steep coal seam with horizontal strata or looselevel, laws of surface deformation are more difficult to predict because of theeffect of two structures.Based on geological data of Qingshan mine in Jiangxi province, this papermakes an attempt study on overburden movement mechanism and laws ofsurface deformation in steep coal seam mining, which with methods oftheoretical analysis, similar material simulation and numerical simulation. Theuseful understanding are as follows:(1) According to strata mechanism characteristics, this paper analyzeoverburden movement, consider that stress can be divided into two componentwhich is normal and tangential forces because of large angle, roof experiencescaving, fracture, bending and sliding along tangent in turn after coal seammining;(2)The paper analyzed stress and deformation situation with the methodsof theoretical mechanism. The roof was be simplified as beam with transverseand axial load. The deflection and slippage was calculated with horizontal andvertical bending theory in mechanics of materials and principle of minimum potential energy in elastic mechanics.(3)Based on caving characteristic of the gob and the state of stress ofstrata, laws of overburden and surface deformation were analyzed. It wasconsidered that asymmetric stress arch existed in horizontal strata near surfaceand maximum subsidence value of ground was in vault.(4)By similar material simulation experiments, different mining thicknessand height in steep coal seam mining were be simulated to analyze differentcaving and deformation shape in different period.(5)In similar material simulation experiments, the subsidence andhorizontal displacement of the survey line in different position were analyzed,and it made strata movement in various location more systematicalunderstanding.(6)The surface subsidence curves of different mining thickness and heightin similar material simulation experiments were analyzed and compared with therules of strata movement.(7) Discrete numerical simulation was utilized to calculate differentmining thickness, mining height, dip angle and horizontal strata thickness insteep coal seam mining. The displacement and vertical stress of the output wereanalyzed, so the factors which can affect overburden movement werequalitatively comprehended.(8)According to the analysis of surface subsidence curves of numericalsimulation and comparison to conclusions of similar material simulationexperiments, internal relations of strata movement and surface deformation weregot. For the movement laws of “overburden-horizontal strata-surface”, withmethods of theoretical analysis, similar material simulation and numericalsimulation, the paper analyzed overburden movement mechanism and laws ofsurface deformation in steep coal seam mining, and offered a reference tocontrol ground of stope and prediction of surface deformation in steep coal seammining.