Design of bolt support for buttock base on surrounding rock classification method of pressure releasing zone

A thickness value L_(p) of the pressure releasing zone is presenting a multi factor comprehensive index.With the thickness value L_p,the rock classification of the pressure releasing zone has effectively overcome the difficulties of the in-situ rock stress,surrounding rock strength,underground water and other factors affected to the surrounding rock stability.The classification method is simple and practical.With the rock classification method of the pressure releasing zone,a bolt support design was made for the two side walls of the seam gateway for No.88301 coal mining face.The results had met the practical requirements of the project.