Study on fracture evolution of surrounding roadway under close distance coal pillar

Aiming at the problem of large deformation of surrounding rock of roadway with coal pillar in near coal seam, based on the geological conditions of Dengmaotong Mine, the UDEC-Trigon numerical model was constructed, and the deformation characteristics and fractures evolution of roadway surrounding rocks were analyzed at the coal pillar center 0 m, 10 m, 20 m and 30 m away from the 2# coal seam. The results showed that during the excavation, the deformation of two walls were serious and the deformation volume was up to 602 mm, which was symmetrically distributed, and the deformation of two walls was asymmetrically distributed, which was 10 m from the center of the coal pillar; during the mining, the deformation degree of roadway was significantly aggravated. It was 10 m away from the center of coal pillar, the roof was vulnerable to instability and failure, and the deformation had asymmetry, at 20 m from the coal pillar center, the deformation of roof and floor was serious, while the deformation at 30 m from the coal pillar center was relatively small. The study shows that the deformation of roadway are significantly different at different locations from the pillar center of 2# coal seam, and the deformation of surrounding rock is positively correlated with the development of fractures, when the deformation of the surrounding rock is small, the main factor is the development of shear fractures, and the instability of surrounding rocks is more likely to be accompanied by the rapid increase of tensile fractures.