Based on global initiatives such as the clean energy transition and the development of renewable energy, the pumped storage power station has become a new and significant way of energy storage and regulation, and its construction environment is more complex than that of a traditional reservoir. In particular, the stability of the rock strata in the underground reservoirs is affected by the seepage pressure and rock stress, which presents some challenges in achieving engineering safety and stability. Using the advantages of the numerical simulation method in dealing deal with nonlinear problems in engineering stability, in this study, the stability of the underground reservoir of the Shidangshan (SDS) pumped storage power station was numerically calculated and quantitatively analyzed based on fluid-structure coupling theory, providing an important reference for the safe operation and management of the underground reservoir. First, using the COMSOL software, a suitable mechanical model was created in accordance with the geological structure and project characteristics of the underground reservoir. Next, the characteristics of the stress field, displacement field, and seepage field after excavation of the underground reservoir were simulated in light of the seepage effect of groundwater on the nearby rock of the underground reservoir. Finally, based on the construction specifications and Molar-Coulomb criterion, a thorough evaluation of the stability of the underground reservoir was performed through simulation of the filling and discharge conditions and anti-seepage strengthening measures. The findings demonstrate that the numerical simulation results have a certain level of reliability and are in accordance with the stress measured in the project area. The underground reservoir excavation resulted in a maximum displacement value of the rock mass around the caverns of 3.56 mm in a typical section, and the safety coefficient of the parts, as determined using the Molar-Coulomb criterion, was higher than 1, indicating that the project as a whole is in a stable state.

The seismic effect of well water level is complex and variable, and even if both wells are located in an area with similar tectonic and hydrogeological conditions, they exhibit slightly varying response characteristics to the same earthquake. Wells BB and RC, located about 100 km apart in the southwest of the Huayingshan fault zone in the Sichuan and Chongqing regions, exhibited obvious similarities and differences in their co-seismically response and sustained recovery characteristics during the Wenchuan Ms8.0 earthquake. Based on the dislocation theory and fluid–solid coupling theory, this study developed the seismic stress–strain model and the response model of pore pressure to seismic stress using Coulomb 3.3 and COMSOL 6.3, respectively. Simulation findings indicate that both BB and RC are located in the expansion zone, where their water levels show a co-seismic step-down. The amplitudes of BB and RC water levels are 83 cm and 81 cm, which are approximately 10 cm smaller than the actual values. The recovery times are 60 d for BB and 3 h for RC, closely resembling the actual values. Furthermore, the numerical results from different scenarios show that the recovery time of pore pressure is reduced by several times when the permeability of the confining layer overlying the observed aquifer increases by one order of magnitude or the thickness decreases, and this change is more sensitive to the permeability. It is clear that the confining condition has an important impact in the response time of sustained changes in well water levels, which may also help to explain the variations in the characteristics of sustained changes in wells BB and RC.

Due to the long duration and high cost of traditional pumping tests, the response of well water levels to seismic waves, earth tides, and barometric pressure provides a feasible method for determining continuous changes in aquifer hydraulic parameters. Aimed at the problem that the response phase shift of well BB water levels to tide M₂ is greater than that of tide O₁, this paper preferentially calculated the time series changes in S, B_e, n, and BK_u based on the response mechanism of well water levels to barometric pressure and earth tides with the help of the smooth moving method. Then, by using the mixed flow model, the variation in the transmissivity and leakage coefficient over time was simultaneously obtained, and the evolution process and characteristics of aquifer parameters near well BB caused by the Wenchuan earthquake are ultimately discussed. The calculation results are basically consistent with the previous pumping test, and have been verified and compared by using other scholars’ methods. This solving process avoids problems such as excessive dependence on initial values, multiple solutions, and unstable tide O₁, which has a promoting effect on the study of the impact of seismic activity on aquifer systems.