Abstract: Based on the geological occurrence conditions of roof and floor steep coal working face and the characteristics of middle and lower caving gangue filling of goaf, the force model of steep coal working face is established by using theory of elastic thin plate, flexure deformation characteristics under overlying strata and inferior goaf filling gangue are studied, and the theoretical calculation formula of goaf filling width and deflection equation of roof deformation is obtained. In light of the field parameter at Xintie mine of Long Mine group in Qitaihe branch, the study have shown that in the steep inclined working face, there is a larger deformation in the roof in the upper part and less deformation in the lower part; maximum deflection is 24 m away from working face end, with maximum deformation 320 mm; In the working surface of coal wall in the front and rear upper coal wall, roof and upper part of caving rock contact office will first appear to stretch or cause shear failure, finally will form an “U”type breaking. Research results conform to actual roof deformation.

Key words: steep seam, main roof, fracture mode, mechanical model, theory of elastic thin plate