Stability and Sealing of Abandoned Roadways Under High Internal Pressure

Abandoned coal mines have many underground space resources, such as roadways, shafts, and gobs. Among them, abandoned roadways are the best gas storage space for underground compressed air energy storage (CAES). However, CAES caverns have high air pressure and strict sealing requirements. Therefore, the stability and sealing of abandoned roadways under high internal pressure must be analyzed. Afterward, the suitability of abandoned roadways used for CAES caverns should be evaluated. In this study, the numerical simulation software FLAC3D was used to calculate the stress, deformation, plastic zone volume, and pore pressure of surrounding rock in an abandoned roadway under 10 MPa internal pressure. The influence of buried depth, surrounding rock grade, and in situ stress state on roadway stability and the effect of surrounding rock permeability on roadway sealing were analyzed. Results showed that the stress, displacement, and plastic zone volume of surrounding rock were affected by high internal pressure when the buried depth was less than 300 m, but high internal pressure had little effect on them when the buried depth was more than 300 m. The suitable range of buried depth was more than 300 m. The optimal choice of surrounding rock grade was I and II, followed by grades III, IV, and V. The optimal choice of in situ stress state was σ H > σ h > σ v , followed by σ H > σ v > σ h and σ v > σ H > σ h . The sensitivity of the stability evaluation parameters was ranked in descending order as follows: buried depth, surrounding rock grade, and in situ stress state. When the surrounding rock permeability was less than 1 × 10 − 14 m 2 , the 24-h air leakage rate of the roadway was less than 1%. The suitable range of surrounding rock permeability was less than 1 × 10 − 14 m 2 .