Structural Analysis Of Instability Behavior For Roof Strata In Shallow Seam

According to intense pressure behavior of the mine working face in shallow coal seam longwall mining of single key stratum, on the basis of previous studies, discuss the basic laws motion of roof breaking, characteristics of structure, the influencing factor of structure stability and the mining stability of relationship between height and roof in shallow seam. Apply the relevant principles of mechanics and combined with the experiment of physical similarity simulation, analysis the breaking step and mechanism of roof in the first weighting and periodic weighting, with the method of combining theoretical calculation and numerical simulation to predict the breaking step in periodic weighting of roof, according to the result of field test to determine the reliability of prediction. The reason of the non-equilibrium characteristics and the motion properties of the broken key stratum in the first weighting, apply the initial post-buckling theory to analysis the roof post-buckling behavior of critical lays in mining process, the motion properties is determined by the terminal subsidence of rock blocks and the horizontal force between rock and rock in non-equilibrium, the study found that there are three kinds of movement forms may occurred after the first weighting: the firstly is the rock blocks cut down along the coal wall and occurred step convergence at last; the secondly is occurred rotary instability of rock blocks after main roof breaking; the thirdly is occurred reverse rotation and lead to step convergence after the rock block touch gangue, and give the criterion of occur corresponding patterns of movement. The mining height is one of the main factors to control the stability of the structural of roof, under the steady of structural of roof to determine the mining height in condition of supporting and unsupported, the results show that the rock can slide from the coal wall in condition of unsupported , the mining height is determined by the subsidence of rock after it breaking; the rock can also occur rotary instability in condition of supporting, the mining height is determined by maximum rotation angle of rock. It provides the certain of basis to research control theory in rock pressure of stope and support theory of stope in further.