The development history, cavern composition and role of underground compressed gas energy storage technology were systematically introduced, and the development status of underground lined cavern technology was discussed. This paper systematically analyzed the research progress of three key problems of underground lined caverns, namely ultimate storage pressure, thermodynamic effects in the process of gas injection and production, and sealing performance of cavern lining, summarized the existing research results, pointed out its limitations, and put forward suggestions for the future research direction of underground lined caverns.

This research summarized the basic concepts of compressed air energy storage(CAES)underground caverns from an engineering perspective, analyzed the basic structure of caverns and the main load characteristics of caverns during operation. On this basis, the basic design concept of flexible sealing structure was put forward, and the reliability design method was suggested to be adopted in the construction of underground caverns, which also provided the guidance and design principles, operation, and maintenance of CAES underground caverns.

Based on groundwater level data of 35 monitoring boreholes from 2015 to 2020 obtained from a large-scale underground water-sealed cavern project, the characteristics and causes of the changes in the groundwater level were systematically analyzed. Taking the construction progress of each cavern unit and geological structure information obtained from previous survey into account, those monitoring data revealed the influence of underground cavern excavation and artificial water curtain system on groundwater level, and the possible risk areas of low water pressure. According to the corresponding relationship between the temporal changes of groundwater level and construction progress, the monitoring boreholes could be divided into three types: water level maintains relatively stable,water level declines when adjacent tunnels were excavated; water level declines far after the adjacent tunnels were excavated. Combined with the spatial distribution of boreholes and the construction progress of underground caverns, it could be found that the groundwater level in the overall study area declined after the excavation of the underground caverns. However, benefited by the artificial water curtain, groundwater level in most area maintained higher than the safe water level(-25 m). Affected by faults F2, F3 and joint fracture zones L4, L8, local groundwater level in the southwest was still far below the safe water level(-25 m)at the end of monitoring, and it indicated a risk of insufficient water sealing. It indicated that the dynamics of the groundwater level in the study area was closely related to the construction progress and quality of the underground caverns, and the systematic monitoring of the groundwater level and timely analysis and feedback were essential. It is urgent to compile a specification for the underground water monitoring of the water-sealed cavern to promote more systematic monitoring of groundwater and improve the construction efficiency of the project.

In order to ensure the stability of the existing operation cavern, the blasting vibration analysis of the drilling and blasting excavation of the adjacent expansion cavern was carried out to clarify its influence on the stability of the existing operation cavern. Based on a domestic underground water-sealed cavern project, ANSYS/LS-DYNA was used to establish a three-dimensional numerical calculation model to carry out blasting vibration simulation, and its impact on the operating cavern was evaluated by peak vibration velocity and effective stress. The results showed that the vibration velocity of the monitoring point in the main cavern 1 was 0.1-0.8 cm/s, and the vibration velocity of the monitoring point in the main cavern 2 was 0.045-0.350 cm/s, and the maximum peak velocity appeared in the direction that was consistent with the propagation direction of the wave. The maximum single-stage explosive quantity affected the peak vibration velocity(combined velocity)and effective stress. The more the explosive quantity, the higher the vibration velocity and effective stress, peak vibration velocity could be increased by up to 200%. Under the condition that the maximum single-stage explosive quantity was less than 65 kg, the effective stress and the combined velocity at the nearest distance from the explosion source were less than the values specified in the safety regulations. The blasting construction of the expansion cavern had little impact on the operating cavern and had no potential safety hazard. Combined with the on-site blasting vibration monitoring data, the correctness of the simulation results was verified.

The stability of surrounding rock within an underground water-sealed cavern project was investigated to examine the stability of surrounding rock under the intersection of multiple faults and underground caverns. The Hoek-Brown modified rock mass physical-mechanical parameters were utilized, and the Mohr-Coulomb model in the FLAC^3D software was employed as a constitutive model. The results showed that the sidewall displacement of the main chamber gradually increased with the progress of the excavation stage. After the entire section was completely excavated, the lateral displacement of the primary cavern's sidewall generally surpassed that of both its vault and bottom plate. Stress concentration and plastic deformation were observed in the sidewalls of most caverns, as well as in the top sections of select caverns. In caverns adjacent to, but not intersecting with faults, unstable rock mass areas were formed between the cavern and the fault, where the rock mass tended to slide into the cavern, resulting in significant displacement. In caverns directly intersecting with faults, the unstable rock mass areas disappeared and a similar displacement pattern was observed as that without faults. Stress release in the surrounding rock was induced by the fault and significant plastic deformation of adjacent rock near the cavern was resulted. In the construction process of an underground water-sealed cavern, the position of the direct fault crossing needs to be monitored, and attention should be paid to its anterior and posterior positions.

In order to deeply understand the design principle and key technology of coal mine roadway oil storage and reconstruction project, the key technologies and engineering applications of coal mine roadway storage and reconstruction engineering were summarized through literature review and specific oil storage engineering cases.The site selection of the abandoned mine for oil storage should ensure that the crust of the mining area was stable, the geological structure was simple, the surrounding rock of the roadway was hard rock or relatively hard rock, the surrounding rock of the roadway was complete or relatively complete, the surrounding rock was weak in permeability and had a stable groundwater level. When the permeability of the surrounding rock of coal mine roadway was relatively discrete, and the water pressure of the surrounding rock was greater than the sum of oil and air pressure in the reservoir, it is necessary to reduce the permeability of the rock mass and carry out reconstruction by hydrodynamic containment method to realize the encapsulation of the roadway of the reservoir and control the leakage of oil products.When calculating the oil storage capacity of the coal mine roadway, it is necessary to consider the geological conditions of the roadway, the water curtain system, the corrective coefficient of the space occupied by the pump pit, the water bedding layer, and the blocking section of the oil storage reservoir, and also the oil supply volume transported from the nearby ports and wharves, so as to finalize the scale of the construction of the oil storage reservoir of coal mine roadway.

Based on the background of an underground water-sealed cavern, curtain grouting technology was introduced to seal the cavern due to the water seepage caused by the development of water-conducting structure in the engineering area. The influence of curtain grouting on the permeability of rock mass and its seepage control effect in the cavern project were studied by means of field tests and numerical simulation. The results showed that during the implementation of curtain grouting in sequence, after Ⅰ-holes grouting, the permeability of the rock mass at the Ⅱ-holes was weakened, and the hydraulic conductivity before grouting and unit ash consumption had a better law of decreasing in sequence. When the permeability of the rock mass was large, it had good groutability and large ash consumption, the hydraulic conductivity and unit ash consumption decreased obviously during grouting in Ⅱ-holes, and the permeability reduction effect of grouting was also more significant. The hydraulic conductivity of Ⅰ-holes in curtain grouting was related to the burial depth of the grouting hole section. Outside the scope of blasting influence, grouting pressure should be increased appropriately to increase ash consumption, and better grouting results may be achieved. The seepage field analysis revealed that the anti-seepage curtain had a positive effect on reducing the permeability of the water-conducting structure within the grouting range, which could partially cut off the seepage of the natural groundwater along the main water-conducting structures into the cavern, and then played a role in controlling the overall water inflow in the cavern to a certain extent.

The research background was the construction of large-scale lined cavern gas storage for a deep anhydrite ore body in Anhui province, the thermal-mechanical coupling analysis method based on ABAQUS finite element software was used, established numerical model under the gravity stress field, the deep cavity multi cycle under different cavern spacing was apart from the temperature, the gas extraction in the process of filling the key stratum structure deformation, stress distribution and the change process.The distribution law of surrounding rock plastic zone and the change process of surface deformation under different cavern spacing were investigated.The results showed that the temperature of the main structural layers was not affected by increasing the cavern spacing.When the cavern spacing was less than 2 times the hole diameter, changing the cavern spacing had obvious effects on the stress and deformation of key structural layers, surface displacement, tensile stress distribution and size of concrete lining, and plastic zone distribution of surrounding rock, and the interaction between gas storage was more significant.When the cavern spacing increased to 2 times the cavern diameter, the interaction between gas storage was no longer obvious, and the increase of cavern spacing had no obvious effect on the stability of gas storage.

To study the performance of system combining common development and energy storage of deep geothermal energy under sustainable development conditions, seven evaluation criteria were defined. Thermal breakthrough time, water level and vertical displacement were used to assess the sustainable development of deep geothermal energy, and total recoverable energy, stored energy, energy gain coefficient and energy recovery efficiency were used to assess the operating performance of proposed system. Based on the well system which consists of two production wells and one injection well in Juancheng geothermal field, the coupled thermo-hydro-mechanical processes subject to seasonal exploitation and storage were demonstrated and the rationality and applicability of proposed evaluation criteria were validated, using the integrated geothermal reservoir model. The results showed that recoverable heat energy could increase about 360% by adding artificial thermal storage into common geothermal reservoir development, and the proposed system could meet the sustainable development demands of thermal breakthrough time, water level and vertical displacement. It is strongly recommended to add energy storage into the future geothermal reservoir development system, which promotes the development and utilization of urban deep geothermal energy on a larger scale and with higher quality.

Based on the theory of Darcy's law and solute transport, this paper took a groundwater-sealed oil depot project on a certain island as the engineering support and conducted numerical simulation research using COMSOL finite element software to analyze the variations in seepage field in caverns under different design schemes. The water-sealed safety of the cavern was evaluated. The development degree of seawater intrusion in the reservoir area was explored. The research indicated that the project required the installation of a horizontal water curtain, and the design pressure value of the horizontal water curtain should not be less than 0.2 MPa. The variation in the depth of the main cavern had a small impact on the water seal, and the recommended buried depth was -45 m. When the main carvern was fully excavated without oil storage, seawater would intrude into the caverns, with seawater intrusion showing a pattern of rapid intrusion followed by gradual intrusion, entering from the bottom of the main cavern.