Development of an Analytical Model and Computational Tool for Geomechanical Stability Assessment of Mine Shafts Adapted as Energy Storage Reservoirs

Repurposing decommissioned mine shafts into energy storage systems (e.g., Compressed Air Energy Storage or pumped-storage hydroelectric plants) requires verifying their integrity under reversed stress state conditions. Given the lack of analytical solutions in the literature dedicated to assessing rigid linings subjected to high internal pressure, this study addresses this research gap .

The objective was to construct a mathematical model based on the Kirsch solution for elastic media and the modified Coulomb-Mohr criterion, incorporating thermal loads. The model was implemented in the proprietary computational tool PRESS-SHAFT.

Verification of the model on a real-case scenario led to conclusions that are counter-intuitive in light of classical mining geomechanics. It was demonstrated that the critical weak link of the structure subjected to pressures up to 8 MPa (the maximum expected value for such facilities) is not the deepest section, but the near-surface zone (0–80 m) . In this area, due to low lithostatic stresses, there is a risk of stability loss via hydraulic fracturing .

Regarding the deep sections of the shaft, the model confirmed general stability at maximum pressure but identified a potential risk of shear failure under unfavorable conditions during the storage discharge cycle (internal pressure drop). Ultimately, it was shown that with the application of reinforcements in the shallow zone, the shaft adaptation is technically safe.