Study On Arching Mechanism And Release Characteristics Of Fully Mechanized Top Coal Caving In Extra-thick Seam

In this paper,the top coal in the extra-thick coal seam mining of Majialiang Coal Mine is studied by theoretical analysis,mechanical experiments and numerical simulations on the physical and mechanical properties,arching mechanism,fracture mechanism and release characteristics of the top coal.The main results are as follows:(1)Laboratory tests the mechanical and physical properties of the Majialiang coal seam and the top and bottom plates,and obtained parameters such as uniaxial compressive strength,uniaxial tensile strength,cohesion and internal friction angle of the coal and rock mass;The displacement test curve verifies the law of coal body failure along the weak surface and provides a test basis for numerical simulation.(2)Theoretical analysis of the mechanism of top coal arching,found that with the increase of top coal moisture content and block size,the probability and stability of top coal arching continue to increase;numerical simulation method is used to study the tail beam swing arching and reducing the top coal block size two types of arching.(3)Through mechanical analysis,it is found that the peak of the supporting pressure in front of the working face is slightly larger than the ultimate strength of the top coal,and the top coal will be broken into irregular blocks,but the crushing effect is not good;increasing the resistance of the bracket is unfavorable to the top coal breaking,mainly increasing the work.The stability of the square top coal is not obvious to the working face;the increase of the thickness of the top coal can enhance the crushing effect of the front coal in the bracket;when the clamping coal is less than 1.5 m from the top coal,the method of repeatedly lifting the bracket is used to break the coal.It is advantageous;when the distance between the clamp and the top beam of the support is greater than 2.0 m,the repeated support of the support is less effective in destroying the clamp,and other methods are needed to increase the breakage of the clamp and increase the release rate of the top coal;The effect is poor and it is not easy to release.(4)Through the numerical calculation and theoretical analysis,the top coal migration and release characteristics of fully mechanized caving mining are studied.It is found that the displacement activity of medium-hard coal is suitable for partitioning.The top coal caving angle is between 60 o and 90 o,which is most beneficial for coal mining.In combination with the actual situation of the mine,the optimal coal caving step of the 14101 fully mechanized caving face is 0.8 m,that is,one knife and one release,and two coal caving methods are adopted for the single wheel spacing.(5)After the industrial test,it indicates that the equipment selection is reasonable,and the coal wall can be effectively controlled;the coal caving effect is good,and no jamming occurs.The paper has 55 pictures,8 tables,and 75 references.Fill in the chart and fill it out.