Research On The Deformation And Leakage Mechanism Of Compressed Air Energy Storage Chamber In Abandoned Mines

The transformation of energy structure towards green and low-carbon has become a consensus among countries around the world,and increasing the proportion of new energy is an important task for China to achieve the carbon peaking and carbon neutrality strategic goal.In recent years,the installed capacity of wind energy,light energy and other new energy sources has been growing continuously.However,its unstable power supply,low energy density and other defects make the direct grid connection have possible damage to grid operation.Compressed air large-scale energy storage technology came into being.Due to the adjustment of industrial policies in China,a large number of underground space resources with good stability have been abandoned,providing gas storage sites for compressed air energy storage.However,the gas alternating load caused by the frequent and rapid injection and extraction process of CAES have adverse effects on the stability of the surrounding rock of abandoned coal mine tunnels and the overall sealing of the structure.Therefore,conducting research on the deformation and leakage mechanism of CAES in underground spaces of abandoned coal mines has scientific and engineering significance.In this paper,the evolution mechanism of structural stability and sealing of cavern surrounding rock and concrete plug under the coupling effect of stress field and seepage field is studied by numerical simulation and testing.The main achievements are as follows:(1)Taking the Daanshan CAES project as the background,the CDEM continuous discontinuous method was used to study the evolution mechanism of deformation and leakage in lining chambers under the coupling effect of pore crack seepage and stress field.The evolution trend of rock stress,deformation,and air leakage rate under cyclic alternating loads was analyzed.The results showed that the stress,deformation,and air leakage rate showed a periodic change of "increasing-slightly decreasing-significantly-decreasing towards equilibrium" with the change of air pressure;The stability of the surrounding rock at the top of the chamber is weaker than that of the side rock,and sufficient safety reserves should be kept during construction and maintenance.A study was conducted on the influence of different tunnel shapes on the stability of the surrounding rock,and it was found that expanding the bottom of the tunnel into a quasi circular shape is more reasonable.Finally,the daily air leakage rate of the lining chamber using C30 concrete was calculated,and founded that it cannot meet the requirement of a leakage rate less than 1%.(2)Developed lining sealing materials suitable for the construction of CAES.Designed orthogonal experimental method to determine the properties of material permeability,uniaxial compressive strength,and elastic modulus under the content of special cement,aggregate gradation,and cement additives with three levels.Sensitivity analysis of materials to various factors was conducted through range and linear regression,and a multivariate parameter model was established.The results indicate that the content of special cement and aggregate gradation are the main controlling factors for changes in physical and mechanical properties,while the influence of cement additives is relatively weak.Finally,CDEM was used to verify the sealing performance of the material in gas storage,and the sealing effect was good(3)A study was conducted on the mechanics seepage evolution mechanism of the contact surface between concrete and surrounding rock during the process of CAES injection and production using a wedge-shaped concrete plug.Based on the load-bearing characteristics of the concrete plug,different deformation and failure modes at both ends were analyzed.The evolution trend of interface opening degree and permeability in the tension section is consistent with the regularity of the surrounding rock,while the compression shear section is opposite.The impact of different inclined angles on overall safety was studied,and the results showed that increasing the inclined angle is beneficial for maintaining the stability of surrounding rock,but the impact is limited.The selection of appropriate inclination angles and the length ratio of tension to compression shear sections for sealing structures is of great significance for engineering safety and economic rationality...