Research On The Overburden Structure Of Fully Mechanized Caving Face In No.2 Coal Seam Of Lingwu Coalfield

Ningdong is one of the thirteen hundred million ton coal bases in our country, the coal production is mainly from No.2 coal seam Lingwu coal field, With the speedy development of the fully mechanized caving face in Lingwu coal field, the structure of the overburden of the fully mechanized caving face has been deeply studied. The study of the structure of the overburden of the fully mechanized caving face is significant for understanding the caving form of the overburden, strengthening the manage of the roof and guiding field producing.In this paper, based on the theory analysis of the overburden structure, contrapose to the engineering geological conditions of the fully mechanized caving face in No.2 Ciyaobao coal mine of Lingwu coalfield,with field monitoring, numerical simulate experiments, similar material simulation tests and theoretical computing methods, the structure of the overburden is studied. With the field monitoring of underground pressure of the fully mechanized caving face,abundant original data is obtained, the underground pressure is summarized along strike as well as along dip direction. With RFPA 2D numerical simulating method, the coal mining process is modeled, and the roof structure, roof caving process and surface moving is analyzed. With physical similar material simulating experiment, the small structure within the vaulted big structure above the fully mechanized caving face is studied.The study shows, underground pressure of the fully mechanized caving face of No.2 coal seam in Lingwu coal field is significant, the dynamic load factor is quite low and the working resistance is bigger than ordinary fully mechanized caving face. There are pressure balance arch structures in the overburden with the advancing of the coal face, the working resistance of the supports are from the interaction of the rocks within the pressure arch and the pressure of the arch spring. The main pressure arch concept is proposed, and the relation of the arch height and face advancing distance before and after the first breaking of the main pressure arch and the stress and moving of arch spring is determined. The characteristics of underground pressure of coal face along strike is significant, the middle of the face has the maximum pressure during period weighting, the pressure peak transfer to the two sides at other times. The interior small structure of pressure arch is beam structure, the first caving of the immediate roof and main roof are fixed-end-beam structures, and are simply-supported- beam structures during period breaking, the immediate roof caving twice and the main roof caving once, the beam structure is proved theoretically at last.