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Numerical simulation and field monitoring are conducted in this study to investigate rock deformation and failure behaviors during excavation of underground cavern group under high in situ stresses in Jinping I Hydropower Station. According to the numerical simulation, large deformation and damage in the surrounding rock mass result in anchorage cable overlimit. The traditional elastoplastic model only considers plastic yielding in rock mass and does not consider the evolution of damage in rock mass, i.e., initiation, propagation and coalescence of cracks. It is found from the numerical results that the damage behaviors of rock masses subjected to high in situ stresses are characterized by the formation of multi-fractured zones, i.e., the zonal disintegration. Theoretical basis, general rules and reinforcement method for zonal disintegration of the surrounding rock masses under high in situ stresses are proposed. The proposed methods are applied to strengthen support measures for construction of Jinping I Hydropower Station.

To increase natural gas storage capacity and further utilize salt mine resources, salt cavern gas storage in the Yunying salt mine, Hubei Province, China, was simultaneously constructed in two different mining layers (K3 and K4). The purpose of this study was to investigate the long-term feasibility of operating salt caverns for gas storage in two mining layers. Based on the geological conditions and sonar test results, the geometric parameters for the salt caverns in the two mining layers were designed, and a 3D geomechanical model was built to predict the cavern stability. The corresponding evaluation index included the displacement, volume shrinkage rate, equivalent strain, and dilatancy factor. The results show that simultaneously operating salt cavern gas storage in two mining layers is feasible, and the operational pressures for the salt caverns in mining layers K3 and K4 should be no less than 4–9 and 7–12 MPa, respectively, to satisfy the stability requirements. The surrounding rock of the salt caverns presents a larger displacement and volume reduction compared with cases in which the salt caverns are operated in a single mining layer. Increasing the injection–withdrawal frequency increases the deformation of the surrounding rock.

Operational asymmetry is a characteristic feature of underground gas storage systems—particularly in salt caverns—where injection phases are typically longer and steadier than withdrawal phases, which are shorter and more abrupt in response to fluctuating energy demand. Although large-scale hydrogen storage in salt caverns remains under development, similar operational patterns are expected once such facilities reach commercial maturity. Understanding how this temporal imbalance influences the mechanical behavior of the cavern is therefore important for assessing long-term performance and supporting the development of robust operational strategies for future hydrogen storage systems. This study introduces a dimensionless parameter, χ , to quantify the temporal asymmetry of cyclic operation. χ accounts not only for the residence times at high and low pressure but also for the different durations required to reach and leave these states. It is defined as the ratio between the effective durations of the high-pressure and low-pressure stages, including both the holding and ramp phases. The numerator represents the total effective time under high-pressure conditions, which includes half of the filling ramp ( 0.5 τ fill ), the full high-pressure holding phase ( τ WGP ), and half of the withdrawal ramp ( 0.5 τ withd ). The denominator represents the complementary effective time under low-pressure conditions, consisting of half of the withdrawal ramp ( 0.5 τ withd ), the full low-pressure holding phase ( τ CGP ), and half of the filling ramp ( 0.5 τ fill ). This formulation expresses the relative exposure of the rock mass to stabilizing (high-stress) versus creep-promoting (low-stress) conditions. A viscoplastic numerical model is developed to reproduce the time-dependent deformation of salt under cyclic pressure loading. Two measurable indicators are analyzed: the vertical displacement at the cavern roof and the volumetric shrinkage associated with viscoplastic mechanical closure. Results show that temporal asymmetry exerts a dominant control on the long-term mechanical response. When χ > 1 —indicating longer effective residence under high pressure—the cavern evolves toward a steady-state equilibrium; when χ < 1 , viscoplastic deformation accelerates, promoting mechanical cavern closure. Comparison with operational data from three underground natural gas storage facilities in the United States is consistent with the χ ranges associated with the stability trends identified numerically. The proposed parameter χ thus provides a physically grounded and practical first-order indicator for interpreting long-term mechanical behavior in future hydrogen storage caverns, within the scope of a viscoplastic mechanical framework that does not explicitly account for damage, fracture, or permeability evolution. Article Highlights Hydrogen production can be used to store the excess from renewable sources. Temporal asymmetry is the key driver of long-term cavern stability. Operational data validate χ as a first-order temporal indicator for future hydrogen storage.

Tensile deformation and damage play an essential role in rock engineering problems. This paper presents a framework for evaluating the stability of a group of anhydrite caverns combining both experimental and numerical methods. In this study, the tensile Young’s modulus and Poisson’s ratio of anhydrite are determined based on the Brazilian disc splitting test. The tests show that the tensile Young’s modulus of anhydrite is less than the compressive Young’s modulus, with a ratio of approximately 0.58–0.91. The tensile Poisson’s ratio is greater than the compressive Poisson’s ratio, with a ratio of approximately 2.47–3.20. Based on the differences between the mechanical parameters (Young’s modulus, Poisson’s ratio) of anhydrite in the tensile and compressive states, a user-defined constitutive model is developed with the Hoek-Brown failure criterion, which describes the tensile and compressive behaviour at a laboratory scale. Finally, a large-scale three-dimensional (3D) anhydrite cavern group located in Anhui Province, China, which was formed by mining activity over the past 10 years, is used as a case study to illustrate the proposed framework. The model for the anhydrite cavern group is established in FLAC3D5.0, and the stability of the anhydrite cavern group used for underground oil storage is then analysed with this model. The simulation results indicate that after the exploitation is completed, there are few plastic zones and tensile elements in the surrounding rock near the cavern group. The maximum value of cavern roof settlement is approximately 5.54 mm. The maximum cavern bottom upheaval is approximately 6.11 mm, and the maximum ground subsidence is approximately 3.0 mm. The results indicate that the Anhui Hengtai anhydrite cavern group possesses good stability potential as an underground oil storage space.

Compressed air energy storage (CAES) caverns transformed from horseshoe‐shaped roadways in abandoned coal mines still face unclear mechanisms of force transfer, especially in the presence of initial damage in the surrounding rock. The shape and size of the initial damage area as well as their effect on cavern stability remain unclear. Due to the complex geometry and multiphysical couplings, traditional numerical algorithms encounter problems of nonconvergence and low accuracy. These challenges can be addressed through numerical simulations with robust convergence and high accuracy. In this study, the damage area shapes of a CAES cavern are first computed using the concept of damage levels. Then, an iteration algorithm is improved using the generalization α method through the error control and one‐way coupling loop for fully coupling equations. Finally, the stability of the CAES cavern with different damage zone shapes is numerically simulated in the thermodynamic process. It is found that this improved algorithm can greatly enhance numerical convergence and accuracy. The nonuniformity of the elastic modulus has a significant impact on the mechanical responses of the CAES cavern. The cavern shape with different damage zones has significant impacts on cavern stability. The initial damage area can delay the responses of temperature and stress. It induces variations of temperature in the range of approximately 1.2 m and variations of stress in the range of 1.5 m from the damage area. Stability analysis of compressed air energy storage caverns transformed from horseshoe‐shapes roadways in an abandoned coal mine is carried out. Both initial damage areas and two cavern shapes are numerically simulated using a one‐way coupling iteration algorithm of an improved generalization α method. Highlights The range and shape of damage zones were obtained through numerical simulations. The generalized α algorithm was improved by separating parameters to enhance convergence and computational efficiency. The temperature and force transfers change with initial damage zones. The compressed air energy storage cavern stability is strongly affected by initial damages and cavern shape transformations.

With rapid urbanization, the utilization of underground space has become an important part of infrastructure. However, the stability of underground spaces such as large caverns remains a key challenge in civil engineering throughout the lifecycle of a project. Traditional methods of stability assessment rely on static models and periodic monitoring and often fail to capture real-time changes in rock behavior, leading to potential safety risks and, in severe cases, even the collapse of underground infrastructure. To address this challenge, this study introduces a digital twin (DT) framework to improve stability assessments and monitor deformations in underground structures. The framework enables the continuous monitoring and adaptive optimization of rock support systems by combining real-time sensor data with virtual simulations. A five-dimensional DT framework comprises physical objects, virtual objects, service systems, DT data, and their interconnections. It incorporates six key modules, which are structure, geology, material, behavior, performance, and environment, to enhance the understanding of cavern stability. The framework is based on Industry Foundation Classes standards to ensure seamless data exchange, interoperability, and the standardized representation of geotechnical and structural data. A seven-step methodology is developed for this framework, encompassing geological assessment, virtual modeling, Building Information Modeling (BIM)-based design, construction processes, real-time monitoring, and optimization strategies. To evaluate its effectiveness, the framework is applied to a case study, demonstrating improvements in deformation monitoring and rock support efficiency. The findings highlight the potential of integrating DT with BIM to enhance safety, reliability, and long-term stability in underground construction projects.

The Cava Madre of Candoglia is a centuries-old mining cavern of significant historical-architectural interest because it is the site from which the marble is extracted for the renovation of the external structure of the Milan Cathedral. This activity is continuous and therefore requires the guarantee of the supply of the same marble that was used for the construction of the Cathedral. Over the time, block extraction and handling techniques have changed and evolved, ensuring their effectiveness and safety. Today diamond wire is used to detach the bank and to cut the blocks. The movement takes place using trucks capable of traveling along the access road to the quarry and transporting the blocks to the processing laboratories. Some geomechanical aspects play a fundamental role: a careful characterization of the rock materials (marble vein and embedding rocks) in the laboratory and on site, a reliable numerical modeling capable of representing the evolution of the stresses and deformations in the rock and in the present support and reinforcement structures, continuous geomechanical monitoring to control the state of stresses and deformations that actually develop in the rocks and support structures.

Geological disposal at deep burial depths is a widely accepted method for the treatment of high-level radioactive waste, in which an underground laboratory is regarded as an essential facility to connect various aspects of the process. To evaluate the excavation-induced stability of the rock mass surrounding the underground laboratory for deep geological disposal of high-level radioactive waste in Beishan, Gansu Province, true three-dimensional geomechanical model tests are carried out for the first time. A model test loading system is developed with an intelligent numerical control function and automatic excavation apparatuses. The variations in the displacement and stress surrounding the caverns are revealed. The test results indicate that after excavation, (1) the surrounding rock deforms toward the cavern with small displacements less than 3 mm; (2) the radial stress is lower, and the tangential stress is higher; tensile stress is induced in certain parts near the intersection of caverns but at a magnitude lower than the tensile strength of the rock; (3) the excavation-induced perturbation reaches approximately 1.5–2.0 times the cave diameter; and (4) the surrounding rock shows stability after excavation due to the favorable geological conditions and the overall high strength of the surrounding rock. Nevertheless, enhanced support via combined bolting and shotcrete are recommended at the crossing sections. The research results verify the rationality of the design scheme and provide important guidance for the construction of underground laboratories for deep underground disposal of high-level radioactive waste.

Rock cavern stability has a close relationship with the uncertain geological parameters, such as the in situ stress, the joint configurations, and the joint mechanical properties. Therefore, the stability of the rock cavern should be studied with variable geological conditions. In this paper, the coupled hydro-mechanical model, which is under the framework of the discontinuous deformation analysis, is developed to study the underground cavern stability when considering the hydraulic pressure after excavation. Variable geological conditions are taken into account to study their impacts on the seepage rate and the cavern stability, including the in situ stress ratio, joint spacing, and joint dip angle. In addition, the two cases with static hydraulic pressure and without hydraulic pressure are also considered for the comparison. The numerical simulations demonstrate that the coupled approach can capture the cavern behavior better than the other two approaches without the coupling effects.

Effective planning of the cavern field involves determining the optimal pillar width between the caverns and the feasible number of caverns based on geological and mining conditions. The proper design of the pillar width is crucial to ensure the stability of the cavern field and the rational utilization of the rock salt deposit. The stability of the pillars is a complex problem influenced by various factors, including rock salt creep, changes in the cavern pressure during operational cycles, mechanical parameters, and failure criteria of the rock salt. To address this problem, the stability of the cavern field in relation to the number of caverns and pillar widths is evaluated. The evaluation is based on the following criteria: displacements, von Mises stress, strength/stress ratio, and safety factor. Three variations of pillar width and three variants of cavern fields, differing in the number of caverns, are considered. Results show that the allowable pillar width is affected by the number of caverns in the cavern field. Moreover, the stability analysis reveals uneven stress and deformation distribution in the cavern field. When the pillar width is 2.0–3.0 times the diameter of a cavern, pillars at the centre exhibit poorer stability than those at the edges of the cavern field. However, with a narrower pillar width, the highest displacements occur at the field's edges. The findings of this study provide a valuable date in the planning, design, and operation of new cavern fields for the underground storage of energy sources such as oil, natural gas, hydrogen, and compressed air in rock salt deposits.