New technology of collaborative work between face mining and bracket withdrawal

Based on the problems that long times mining connection, complicated process, low coal recovery rate between the last longwall working face and the coal pillar recovery working face of the existing mining area, and large amount of engineering in support withdrawal, combined with the geological and production conditions of No.182312 (abbreviated as No.312) longwall working face and No.182312 outer (referred to as No.312 outer)coal pillar recovery working face in the third mining area of No.2 coal seam in Wutongzhuang Coal Mine, theoretical analysis and industrial test and other research methods was used, the new technology of collaborative work between face mining and bracket withdrawal was put forward:the No.312 outer working surface production system was completed during the No.312 working face recovery process, the No.312 working face passed through the uphill without coal pillars and uphill was retained with support.When the No.312 outer working face was pushed on to the gob-side entry retaining section, the bracket was retracted while pushing the No.312 outer working face.The results have showed:abutment pressure peak superposition area was calculated 7.2 m by limit equilibrium zone formula; the width of the coal pillar is calculated 6.6～7.7 m from different bracket roof-control area under the pressure arch load; it was finally determined that the coal pillar was 8 m before the No.312 working face passed through uphill.Analyzed different fracture modes of basic top and their pressure regulation mechanism, calculated and analyzed that the basic top pre-fracture position was advanced the reasonable fracture position 1.4 m, therefore, stopped mining for 16 h and the bracket was with high resistance.Reinforcement support measures in the uphill was completed before the No.312 working face was 50 m away from uphill; started lanyard and paving when No.312 working face was 14 m away from stopping line; and the air duct cloth was laying within the range of 13～2.4 m from the stopping line; the process of gob-side entry retaining with bracket was formulated after the No.312 working face passed through the uphill.Began recovering the coal pillars after the completion of gob-side entry retaining; when the No.312 outer working face was pushed to the gob-side entry retaining section, the bracket was retracted while pushing the No.312 outer working face with the method of shielding type stepping bracket withdrawal.This technology realized that the uphill has three functions.The coal recovery rate and work efficiency have been improved, the process of working face connection and bracket retraction have been simplified, the amount of roadway engineering and maintenance costs have been saved.Finally, the collaborative work of working face recovery and bracket withdrawal was realized.