Numerical analysis of stress and deformation characteristics of compressed air energy storage chambers developed from a modified coal mine tunnel

Abstract

Abstract The use of abandoned coal mine tunnels as underground compressed air energy storage (CAES) facilities has garnered significant attention given that it effectively repurposes unused underground space and enhances the efficiency of renewable energy utilization. However, existing coal mine tunnels, without optimization and retrofitting, may not meet the stability requirements of compressed air energy storage repositories. Sectional transformation is a retrofitting method with excellent optimization effects. In this study, numerical simulation based on Midas software was employed to create a three-dimensional model of straight-wall arched mine tunnels. The stress and displacement deformation of the tunnel sections were simulated under internal pressure of 10 MPa, and scenarios with no modification and circular-section backfilling were compared. The outcomes of the study are (1) For deeply buried soft rock mines, the existing structure without modification may not meet the stability requirements of compressed air storage facility due to low rock strength. (2) In the unmodified scenario, stress concentration effects and excessive floor tensile stress occur near the tunnel closure. (3) Backfilling straight-wall arched tunnels into circular shapes effectively reduces stress and displacement along the tunnel walls, preventing stress concentration near the tunnel closure. This study provides a retrofitting approach for repurposing abandoned mines into compressed air energy storage facilities, providing guidance for future projects facing complex geological conditions.