Abstract: After coal seam mining, different abutment pressure zones are formed around goaf area, and the stress unloading and concentration can be passed to the deeper floors, then the destroy depth and scope of floors are also affected. In this paper, the half-infinite body model was established which comprehensively considered the stress characteristics in the strike and inclined directions of the working face, and the iterative formula of vertical stress in floors was calculated. Meanwhile, the stress distributions in floors with different depths were calculated by Software-MATHCAD. The results show that the stress contours in different floor strata present oval shapes, and the contour gradient in shallow strata is larger than that in deeper strata. Based on the stress analysis results and Mohr-Coulomb criteria, the maximum damaged depth in floor of one mine was calculated to 14.8 m, while the largest damaged depth of floor by field seismic monitoring was 15.2 m, which are identical with each other. The results in this paper can provide theory basis for surrounding rock controlling and safety mining above confined water.

Key words: floor, stress distribution, stress transfer, damage law