Mechanism and surrounding rock control of roadway driving along gob in shallow buried,large mining height and small coal pillars by roof cutting

In view of problems existing in large coal pillars and small coal pillars for roadway maintenance,theoretical analysis,numerical simulation and field measurement are used to study gob-side entry developed by roof cutting for destress and surrounding rock control in Fusheng Coal Mine with a large mining height of 6 m.Following conclusions are obtained:① Position of main roof fracture can be artificially determined by pressure relief with roof cutting realizing the active pressure control.After roof cutting,the original stress transfer path of the main roof is transformed,the pressure is effectively transferred to the gob,reducing the abutment pressure and avoiding excessive stress from transferring to the solid surrounding rock,gob side entry surrounding rock stress is more uniform and gentler;② Roof fracture structure changes after the roof is cut,before the first weighting,the fixed sides of the main roof change from four to three.After the first weighting,the fixed sides of the main roof change from three to two.The collapse interval is correspondingly reduced.The roof is more likely to collapse.The pressure of the working face also appears gentler;③ Cutting angle,cutting depth,cutting hole space and layout are the keys to the precise roof cutting.A 16 m cutting depth can cut off the main roof of limestone,which can effectively reduce the length of overhanging roof of main roof,cut off the continuous stress.Also,this makes a full use of the bulking and support capacity of caved rocks in the gob;④ Numerical simulations under the three conditions show that the traditional coal pillar of 25 m is too large,causing a lot of waste of resources,and the peak pressure is 18.2 MPa.The supporting pressure of the pillar is the largest with a peak value of 19.3 MPa if only a 8 m of small coal pillar is used without roof cutting,which may lead to failure of gob side entry.The plastic zone of the coal pillar and its surrounding rock under the condition of a small coal pillar of 8 m with roof cutting is the smallest,and the supporting pressure of the small coal pillar is the smallest with a peak value of 12.7 MPa,and the goaf stress is increased to 0.11 MPa.Combined with cutting roof pressure relief,the active control of surrounding rock pressure is realized;⑤ Mine site practice shows that pre split roof cutting and support technology can ensure the stability of surrounding rock during the heading phase and the mining phase along the gob.This study provides a reference and support for the safe and high efficiency mines under similar conditions.