Spatial and temporal stability analysis and assessment of underground powerhouse caverns: A case study

Abstract

The spatial and temporal deformation features are important representations for stability analysis and assessment of the underground powerhouse. However, due to the excavation disturbance and sensors failure, the in-situ monitoring data may be of low quality. To reconstruct the actual project and analyze the full deformation characteristics of the underground powerhouse located in the Suki Kinari hydropower station, a BIM-based parametric geometry model of the caverns and the refined geological model are combined. An elaborate numerical analysis is implemented to discuss the spatial and temporal deformation features, and then, the deformation and failure mechanism has also been revealed. Results indicate that the deformation is time-dependent in a ladder form with the excavation process, and the deformation of rock mass is affected severely by the excavation of the corresponding and the following layers. Besides, the deformation values descend with the monitoring depth increasing. The excavation disturbed area enlarges with the unloading process, and the deformation at the corresponding position keeps deteriorating until new stability. For rock mass at the arch crown, nearly 90% of the total deformation occurs at the first layer excavation, indicating that immediate support is crucial. Besides, the deformation of rock mass at various depths is generally divided into three zones according to the decrement rate and magnitude. Furthermore, the failure of the surrounding rock mass is induced by the radial stress reduction and tangential stress increment, leading to excavation damage. Therefore, supporting strategies can be imposed to prevent stress variation.