Study on Floor Deformation and Failure Law of Deep Mining Coal Seam

The determination of the floor failure depth by mining is the key and preconditions for realizing deep mining of the coal seams which buried deeply and were subjected to the threat of the confined water in a mine.Based on the hydro-geological conditions of 1305 working face in this mine,the mechanical properties of coal seams and the structure and properties of roof and floor rock strata,study was made on the distribution characteristics of stress and plastic zone in the deep mining process by using FLAC3D numerical simulation method.Finally,it obtained that the floor failure depth of the seam being mined is about 22m according to the measurement data at the site and the observation rule of the ultrasonic images of seam floor and roof in different depth.