**3. Methodology**

In this paper, theoretical analysis, numerical simulation and engineering application are used to study the instability mechanism and stability control technology of the surrounding rock of the mining roadway below the remaining coal pillar. The technical flowchart is shown in Figure 3. The specific steps are as follows: (1) Through the theoretical analysis method, the superposition effect of T-shaped residual coal pillar on the abutment pressure of 4-2 coal seam in 2-2 coal seam of Buertai Coal Mine is studied, and combined with the Mohr-Coulomb criterion, the failure and instability mechanism of surrounding rock of 42202 mining roadway under multiple disturbances is revealed. (2) On the basis of theoretical analysis, an equal scale numerical model is established by using FLAC3D numerical software (version 6.00.74, Itasca, China, 2020) to simulate and analyze the surrounding rock plastic zone and vertical stress distribution characteristics of 42202 mining roadway under different layout schemes (different width section pillars), so as to propose the most reasonable section pillar retaining scheme, and propose the surrounding rock reinforcement support technology to control the roadway stability. (3) The scheme of section coal pillar reservation and the technology of surrounding rock reinforcement and support were applied in the 4-2 coal seam, and the effectiveness of the research results in this paper is verified through ground pressure monitoring.
