Study On Overburden Deformation Movement Law Under Thickly Unconsolidated Layer In Seam Mining Of Zhaogu No.1 Coal Mine

In some mining areas of the eastern and central parts of China,the bedrock overlying is relatively thin,but the unconsolidated layer is thicker.The movement law of deformation of overlying bedrock and thick unconsolidated layer in coal seam mining is different from the general geological conditions.the accident of sand-blasting ?water-splashing and Support Break-off occurred around the roof of the working face,which seriously affects the safe and efficient production of coal mines.the coal seam mined belongs to a nearly horizontal thick coal seam in the Zhaogu No.1 Mine.the paper is based on the engineering background of the unconsolidated thick layer and thin bedrock of the 16011 working face of the Zhaogu No.1 mine.using similar simulation tests,numerical calculations and field observations,the law of deformation and movement of the unconsolidated layer and bedrock layer on fully mechanized mining face is systematically studied.the unconsolidated layer of Zhaogu No.1 Mine directly covers the upper part of the bedrock of the coal seam.the unconsolidated layer consists of clay,sandy clay,gravel and fine sand,the average thickness is 453 m.similar simulation test results show that In the process of coal seam mining,there are collapse zones and fracture zones in the bedrock layer,and the caving-height ratio and the crack and mining ratio are 4.2 and 9.4.With the advancement of the fully mechanized mining face,a "Unconsolidated arch" mechanical structure is formed in the thick Unconsolidated layer of the upper part of the bedrock.The structure transfers the overburden load to the surrounding of the goaf,so that the fully mechanized mining face in the arch is in the low stress zone.The bearing characteristics of the key layer structure and the shape of the unconsolidated arch structure in the bedrock are studied.The unconsolidated arch is an ellipse of the direction in which the working face advances,and the height of the unconsolidated arch is related to the advancement of the working face and the lateral pressure coefficient.As the degree of advancement of the working surface increases,the height of the unconsolidated arch gradually increases,and the height of the unconsolidated layer is positively changed with the advancement of the working surface.As the lateral pressure coefficient increases,the height of the unconsolidated arch gradually decreases.The on-site ore pressure observation results show that the initial pressure step of the roof of the fully mechanized mining face is 45 m,the pressure step is 12.5m,and the average dynamic load factor during the period is 1.3.25 m ahead of the working face is the mining affected zone,and the roadway deformation is seriously damaged.The research conclusions provide reference and reference for the safe and efficient opening of coal seams under thin bedrock and thick and loose layers.