Research on the width of coal pillar and flexible anchor cable support technology based on the evolution of plastic zone

Roadway driving along goaf can effectively improve the recovery rate of coal resources and the mining replacement relationship, but it is difficult to construct and maintain. In order to improve the stability of surrounding rock of gob side entry and reduce coal loss, taking 42108 auxiliary haulage roadway of Bultai Coal Mine as the research background, the development characteristics of plastic zone of roadway are determined through theoretical analysis, a numerical model is established to comprehensively determine the reasonable width of coal pillar and industrial practice is carried out. The research results show that the 42108 auxiliary haulage roadway has the characteristics of large deformation of the side under the influence of mining after being excavated. The theoretical analysis results show that the plastic zone of the auxiliary haulage roadway is distributed in an asymmetric butterfly shape, and the development range of the plastic zone is 1.8-2.7 m. Combined with limit equilibrium theory and numerical simulation, it is considered that when the width of coal pillar is greater than 30 m, there is an obvious stress reduction area in its interior, which is conducive to roadway maintenance. At the same time, considering the recovery rate of coal resources, the reasonable width of coal pillar is determined to be 30 m. It is revealed that the reason why the tunnel deformation cannot be effectively controlled by multiple reinforcement support is that the anchor cable is easy to stretch and break. On this basis, a flexible anchor cable support scheme is proposed, and the row spacing between the side bolts is reduced to 750 mm× 750 mm, the maximum deformation of both sides within 30 days after field practice is 160 mm, and the surrounding rock control effect is significant.