Three-dimensional stress evolution and comprehensive treatment technology for super-long working face across abandoned roadway with large section

In order to solved the problem of super-long working face across abandoned roadway with large section, which is easy to cause rib spalling and roof falling, based on a super-long working face in Chengzhuang mine of Jincheng, a three-dimensional model of abandoned with large section roadway was established. The roof of working face was divided into three parts: coal pillar roof, abandoned roadway roof and mining area roof. The criterion of pillar instability was deduced and the roof stress evolution process of large section abandoned roadway was analyzed by FLAC^3D numerical simulation. The results show that when the W was equal or less than 40 m, the advance support stress of working face and the advance support stress of empty roadway were superimposed on the coal pillar with the plastic deformation of coal pillar; When W was equal or less than 10 m, the roof stress of coal pillar gradually reached its peak value of 16.6 MPa, and the coal pillar was destroyed and lost its bearing capacity. The roof stress of abandoned roadway reached its peak value of 12.7 MPa. According to the evolution law, the reasonable strength of filling pillar and grouting reinforcement opportunity were identified. The comprehensive treatment technology for abandoned roadway with large section was proposed.