Stability analysis and control strategy of layered floor of mining roadway under different coal pillar size

The coal pillar size has a significant impact on the stress environment of layered floor of mining roadway. Taking the auxiliary haulage roadway of Meihuajing Mine as the engineering background, the comprehensive research methods of on-site investigation, theoretical analysis, numerical calculation and field test are used to analyze the stability of the floor under different stress environments, and the targeted control countermeasures are proposed based on the specific engineering examples. The research shows that under the influence of mining stress field, the stress environment of the floor on both sides of the auxiliary transportation roadway is different, which causes the difference of deformation and failure of the floor on both sides of the roadway. The transversely isotropic body is used to characterize the layered characteristics of the floor. The mechanical calculation model of the roadway floor is established, and the stress expression at any point of the floor under mining influence is derived, so as to obtain the influence of the coal pillar size effect on the stress environment of the floor. Based on the Mohr-Coulomb criterion, the layered floor failure criterion is constructed, and the floor failure patterns under different coal pillar sizes are obtained. Under the condition of small coal pillar, layered floor exists in asymmetric stress environment, and its failure pattern is in an asymmetric saddle shape. When the coal pillar size increases to a certain extent, the difference in the surrounding rock stress on both sides of the floor decreases, and the failure form of the floor gradually becomes symmetrical. In order to achieve fine control of the surrounding rock of the mining roadway, the supporting scheme should be adapted to the change of the surrounding rock stress environment. According to the difference of coal pillar size, based on the surrounding rock control countermeasures, the roadway surrounding rock control technology is proposed combining differentiated support and symmetrical support. Numerical calculation and field engineering application results show that the supporting system could adapt well to different stress environments of surrounding rock, and form a cooperative bearing system with the surrounding rock, and the supporting effect is good. © 2023 China University of Mining and Technology. All rights reserved.