Theoretical analysis on coal wall stability of fully mechanized 8.5m high cutting longwall mining face

The spalling problems of a fullymechanized high mining face was one of the major factors affected to the high efficient and safe-ty mining. In order to study the high cutting mining affected to the stability of the coal mining wall,based on the surrounding rock mechan-ics conditions of the 8. 5 m high cutting mining face in No.1-2 Seam of No.4 Mining Block in Shangwan Mine,a compressive bar theorywas applied to analyze the bending features of the coal wall and a location of the coal wall easy to cause spalling obtained was at the mid-dle-upper part of the coal wall. A ladder slide model was provided. In consideration of the friction force,with the mechanics calculati on,a conclusion on the sidewall protection force no less than 0. 251 MPa was obtained. According to the 8. 5 m ultra highfullymechanized coal mining face,a support metho d with a pressure increased and force increased compound sidewall protection mechanismof the powered support was provided. The sidewall protection plate with a length of 1 100,1 600 and 800 mm individually and a total lengthof 3 500 mm could effectively reduce the large area spalling phenomenon occurred in the coal mining face.