Study On Failure Law Of Surrounding Rock And Overlying Bed In Steep And Specially Thick Coal Seam Mining

In this paper, comprehensive researches are carried on the law of coal and rock movement of horizontal section top caving in steep seam, damage characters and surrounding rock control . Creative results were educed in experiment, theoretical analysis, numerical simulation and engineering practice.First, based on similar material model test, top coal cave-in characters in steep and thick seam were studied as well as failure law of main roof and features of surface subsiding.Applying damage statistical mechanics theory, general formulas to determine cave-in height of top coal are given, and factors affecting top coal caving are analyzed .With the help of classical sheet theory in elasticity mechanics, deformation and failure law of main roof is analyzed when the gob area is packed and not packed. It is pointed out that the law of main roof beak in top caving in steep and thick seam initially occur at the middle of exposed main roof surface and expand along the face advancing direction which is different from it in gently inclined coal seam.According to numerical simulation, displacement and stress changes in different horizontal section height are presented. The distance changing trends without marginal coal pillar were induced an well. The law of distance and stress change of main roof is also described while applying filling method mining.The coupling failure mechanics of coal and rock mass are analyzed in theory, It is revealed that there exists large scale surrounding rock mass catastrophe in large volume gob areas when mining in steep and thick seam. Thus a scientific method to control surface damages is brought out based on different section in damage evolution of coal and rock, slop stability mechanics around sink pit caving in steep and thick seam and filling gob area with self-weight.