Surrounding rock stability of underground water-sealed caverns based on feedback of multi-source monitoring

ObjectiveUnder complex geological conditions, the mechanical properties of the surrounding rock in underground water-sealed caverns are weakened due to construction disturbances, accompanied by stress redistribution and deformation accumulation, which leads to the increased risk of local instability. The creep effect further exacerbates the deformation and plastic failure of the surrounding rock, posing a threat to the long-term stability of the caverns. Therefore, the study of surrounding rock stability should fully utilize monitoring data to assess the state of the surrounding rock and guide construction and operation. MethodsBased on the comprehensive analysis of multi-source monitoring data, including surrounding rock displacement, anchor bolt stress, and borehole wave velocity, numerical experiments with orthogonal design were adopted to invert the mechanical parameters of the rock mass. Meanwhile, the characteristics of pore water pressure, surrounding rock deformation laws, stress variation, and plastic zone distribution characteristics under layered excavation of the cavern during construction were analyzed. Finally, the stability characteristics of the underground water-sealed storage cavern under long-term water-sealing conditions were evaluated using a creep model of the underground cavern group. ResultsThe results show that the deformation of the surrounding rock sharply increases when passing through the monitored section during excavation, with a maximum increment of approximately 3 mm, and then tends to converge. The area affected by the J1 jointed dense zone has a higher displacement value. The overall stress of the anchor rod system is relatively low, and the anchor bolt stress changes synchronously with the surrounding rock deformation. The depth of the loosening zone of the surrounding rock is approximately 1.0 m. During construction period, the pore water pressure in the excavation area approaches 0 MPa, and the seepage flow of caverns and deformation of surrounding rock are densely distributed along the J1 jointed exhibits zone. The excavation of the middle and lower layers causes the displacement at the intersection of J1 and the arch line to increase by 90.4% and 28.7%, respectively. The plastic zone in the sidewalls deepens layer by layer, with a maximum depth of 9.2 m. The long-term deformation characteristics of the surrounding rock are manifested as sidewall convergence > floor uplift > crown settlement. The cumulative deformation at the intersection of the J1 and the arch line during the first year accounts for 92% of the total deformation over 30 years, with a maximum cumulative deformation of 27.1 mm. Under the creep effect, stress is gradually released, and the stress distribution tends to become more uniform. The plastic zone near the J1 expands significantly, while the plastic range in the intact granite area is relatively small, indicating higher long-term stability, indicating that the geological structure-affected zone is the main instability risk zone of the surrounding rock in underground water-sealed caverns. ConclusionThis study provides engineering significance and reference value for stability evaluation during both the construction and operational phases of underground water-sealed caverns.