Underwater compressed air energy storage was developed from its terrestrial counterpart. It has also evolved to underwater compressed natural gas and hydrogen energy storage in recent years. UWCGES is a promising energy storage technology for the marine environment and subsequently of recent significant interest attention. However, it is still immature. In this study, the latest progress in both academic and industrial fields is summarized. Additionally, challenges facing this emerging technology are analyzed. The pros and cons of UWCGES are provided and are differentiated from the terrestrial variant. Technical, economic, environmental, and policy challenges are examined. In particular, the critical issues for developing artificial large and ultra-large underwater gas storage accumulators and effective underwater gas transportation are comprehensively analyzed. Finally, the demand for marine energy storage technology is briefly summarized, and the potential application scenarios and application modes of underwater compressed gas energy storage technology are prospected. This study aims to highlight the current state of the UWCGES sector and provide some guidance and reference for theoretical research and industrial development.

The first hard rock shallow-lined underground CAES cavern in China has been excavated to conduct a thermodynamic process and heat exchange system for practice. The thermodynamic equations for the solid and air region are compiled into the fluent two-dimensional axisymmetric model through user-defined functions. The temperature regulation model and experimental study results show that the charging time determines the air temperature and fluctuates dramatically under different charging flow rates. The average air temperature increases with increasing charging flow and decreasing charging time, fluctuating between 62.5 °C and −40.4 °C during the charging and discharging processes. The temperature would reach above 40 °C within the first 40 min of the initial pressurization stage, and the humidity decreases rapidly within a short time. The use of the heat exchange system can effectively control the cavern temperature within a small range (20–40 °C). The temperature rises and regularly falls with the control system’s switch. An inverse relationship between the temperature and humidity and water vapor can be seen in the first hour of the initial discharging. The maximum noise is 92 and 87 decibels in the deflation process.

Based on deformation monitoring and stability results obtained from geological mapping, geological drilling, macrolaboratory, and microlaboratory tests, the sliding mechanism of landslide in Guzhang County of Yongji expressway was studied. The bedding slope landslide results from cutting slope along the central white mud clay slip, and by on-site investigation and deep displacement monitoring, the clay is determined as the landslide surface. Combining the experimental results and similar geotechnical engineering experience, by back-calculation, the parameters of the soft interlayer are calculated as (5 kPa) and (8.5°). Based on X-ray diffraction (XRD) and X-ray fluorescence spectroscopy (XRF) test, the results are concluded that the chlorite in clay interlayer is easily water softened, excavation slope after long-term heavy rainfall chlorite clay interlayer softening. Sustained rainfall and underground water levels showed a positive correlation when the slope is sliding, and the heavy rainfall continued to accelerate slope sliding. Furthermore, the slope surface displacement and profound displacement increase quickly, and rainfall and slope displacement also showed a positive correlation.

An analytical approach for the estimating of critical seismic acceleration of rock slopes was proposed in this study. Based on the 3D horn failure model, the critical seismic acceleration coefficient of rock slopes was conducted with the modified Hoek–Brown (MHB) failure criterion in the framework of upper-bound theory for the first time. The nonlinear Hoek–Brown failure criterion is incorporated into the three-dimensional rotational failure mechanism, and a generalized tangent technique is introduced and employed to convert the nonlinear Hoek–Brown failure criterion into a linear criterion. The critical seismic acceleration coefficients obtained from this study were validated by the numerical simulation results based on finite element limit analysis. The agreement showed that the proposed method is effective. Finally, design charts were provided for exceptional cases for practical use in rock engineering.