Study On The Stability Of Surrounding Rock Of Pingjiang Pilot Cavern For Compressed Air Energy Storage

Compressed air energy storage(CAES)is a large-scale energy storage technology.It has broad application prospects on account of the advantages of large capacity,long-term storage,good economic performance,safety and reliability.As a large-scale compressed air energy storage technology facility,artificial underground storage chamber has attracted more and more scholar's attention.This paper conducts the numerical study of the Pingjiang pilot cavern for compressed air energy storage in Hunan Province and establishes a three-dimensional numerical model based on pilot cavern design results and its surrounding rock geological conditions.Moreover,the thermodynamic coupling numerical analysis method is employed to make further research on the stress and deformation distribution characteristics of Pingjiang pilot cavern for compressed air energy storage under the action of charge and discharge temperature and pressure cycle.The main results are as follows:1.Under the action of the air pressure and temperature cycling of the pilot cavern,the temperature,displacement and stress of the measuring point within extent 3m of the wall of the pilot cavern presented significant cyclical change.The periodical change characteristics of temperature,displacement and stress of the measuring point beyond 3m of the surrounding rock are not obvious.The temperature change of the surrounding rock within 0.5m of the wall is basically synchronized with the temperature of the compressed air,and the temperature variation of the surrounding rock beyond 0.5m of the wall lagged significantly.2.The stress and deformation of the pilot cavern structure are remarkably influenced by the temperature.The displacement value of the measured point with the consideration of the temperature stress is slightly larger than that of the temperature stress without the consideration of the temperature stress,and the difference between them is about 0?0.5mm.The first and third principal stresses are close to each other under the two different conditions,while the difference in stress value in the surrounding rock is relatively large,with the difference of about 0?0.8MPa.3.When the pilot cavern suffers the maximum pressure,the heat exchange between the compressed air and the sealing layer causes the wall temperature of most of the position to rise to about 38?,and the temperature of the sealing layer near the comer of the plug can reach 58?.Sealing compressive stress is generally around 10.OMPa.The local stress concentration also appears in the sealing layer near the comer of the plug and its stress is about 14.1MPa.The tensile stress is generally about 2MPa,which is relatively small.Concrete lining and the surrounding rock produced a maximum of about-lOMPa and 7MPa compressive stress.Besides,the generation of tensile stress is relatively small,about 1.8MPa and 0.6MPa.The maximum value of radial displacement of each structural layer of the pilot cavern is less than 1mm,and the security and stability of the pilot cavern is better under normal operation.4.The temperature,stress and deformation of the pilot cavern are remarkably influenced by the material properties of the sealing layer(different types of materials).When the pilot cavern is under the maximum storage pressure,the temperature of the sealing layer of rubber is 2 to 3 times of that with the sealing layer of FRP and steel plate.The temperature increment of the surrounding rock with the rubber seal layer is minimal.The deformation of rubber seal layer is the largest,and the radial displacement value of surrounding rock is the smallest with steel plate sealing layer.The inner surface of the steel seal layer is subjected to the largest tensile stress.The tensile stress at the wall is relatively small,and the compressive stress is basically the same as that of the compressed air as the sealant material is FRP and rubber.The material of the sealing layer produces less influence on the compressive stress distribution and numerical value of the surrounding rock.Taking into account the stress,deformation,economy and other factors of the pilot cavern,FRP is the most suitable sealing layer material.