Development and application of a model test system for compressed air energy storage using underground space with soft surrounding rock of abandoned coal mines

Compressed Air Energy Storage (CAES) presents a promising and scalable approach for utilizing underground space resources in abandoned coal mines. However, the understanding of the stress and deformation behavior of the composite structure of gas storage cavern using coal mines under high pressure is deficient, which poses a significant barrier to its development. To address this issue, a large-scale model test system was developed to simulate the CAES in soft rock underground spaces of coal mines, the system which mainly consists of an electro-hydraulic servo controlled large-scale true triaxial loading platform, a high-air-pressure loading control system, a system for simulating the composite structure of a CAES chamber, and a data monitoring system. The electro-hydraulic servo controlled large-scale true triaxial loading platform is used to simulate the initial ground stress. The high-air-pressure loading control system is used for precise control of air charging and discharging, consisting of an air compressor, high-pressure air tank, control system, high-pressure pipeline, pressure valve, and pressure gauge, is used for precise regulation of air charging and discharging. Based on the similarity theory, the system for simulating the composite structure of a CAES chamber is, mimicks the composite structure composed of soft rock-reinforced concrete lining-slip layer-sealing layer. The data monitoring system includes sensors for strain, pressure, temperature, etc., optical fiber cables, and supporting data acquisition and analysis instruments and software to monitor the evolutions of key parameters during the test process. Model tests were conducted under different ground stress combinations, cyclic charging and discharging, and high-air-pressure holding conditions to meet the research needs of the Caozhuang coal mine CAES projects. The results show that the developed test system can obtain the stress and deformation behavior of the composite structure of a CAES chamber under different working conditions, making it a powerful tool for further research. © 2024 China University of Mining and Technology. All rights reserved.