| The joint action of strike angle and dip angle specializes the coal wall damaging,the top coal moving,the supports undertaking and the roof controlling of the fully mechanized caving face with large strike and inclined angle.This paper systematically analyzes the fracture characteristics of top coal and coal wall,the movement law of the top coal,the mechanism of supports instability and the roof control of the end caving area of the working face by means of theoretical analysis,numerical simulation and field test.The main research results are as follows:(1)Analyzes the destructing characteristic of the top coal and the top coal is divided into 5 areas: scattered caving area,tension shear failure area,compression shear failure area,loose area and undamaged area according to the distribution of plastic area.By studying the instability mechanism of the coal wall,the paper reveals that the failure surface in front of coal wall in fully mechanized top coal caving face is composed of conjugate shear planes with opposite direction,and in the condition of tough top coal,the failure surface contains one group of conjugate shear planes,and the intersection point of conjugate planes moves down and finally the conjugate shear planes turns to a single shear plane,and due to which,the mechanical model of plastic failure slip line of coal wall is established.According to the slip line theory,the failure and instability conditions of coal wall in large strike and inclined angle fully mechanized caving face are analyzed to propose the corresponding failure and instability criteria.(2)Studys the influence of different dip angles of the coal seam on the top coal movement law,and it is found that with the increase of the dip angle of the working face the deflection speed of the symmetry axis of the caving body and the increase speed of the dip angle are not synchronous,and the coal rock interface will become unsymmetrical with the increase of the dip angle,but the initial shape of the ellipsoid of the caving coal gangue in the fully mechanized caving face under different dip angles is in the shape of "long axis constant approximate plumb"(3)According to the characteristics of the top coal movement and the theory of the ellipsoid,the movement equations of the ellipsoid,the loose ellipsoid and the coal gangue interface(two bodies and one side)in the process of the top coal movement are derived.On this basis,the determination method of the top coal movement track is put forward,and the "two bodies and one side" dynamic curve is determined and drawn.(4)Based on the influence of top coal movement characteristic during the roof coal caving on the distribution of support stress,according to the influence of strike angle of the coal seam on the stability of support tendency,and the influence of inclined angle of the coal seam on the stability of support trend,the paper establishes the mechanical model of support surrounding rock in high angle fully mechanized caving face.Derives the calculation formulas of critical working resistance and critical dumping(sliding)angle of support in different periods to propose the stability control technology of different instability modes.(5)Analyzes the mechanical model of the arc hinged plate structure under the condition of the end caving of the large angle fully mechanized caving face and the roof stability control mechanism of the end caving area.Study the relationship between the end support and the surrounding rock of the large angle fully mechanized caving face and determine the design key and main technical parameters of the end caving support of the large angle fully mechanized caving face.Propose the two section "main and auxiliary frame type of high caving and low rake" end inner support and three section "symmetrical frame type" end bracket of high-level and low-level rake,and analyzes its main characteristics,specific support mode and key technology of stability control.There are 143 figures,15 tables and 203 references in this paper. |
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