Deformation characteristics observed during multi-step excavation of underground oil storage caverns based on field monitoring and numerical simulation

Abstract

The sequential excavation method (SEM) is extremely useful for excavating caverns with high sidewalls and large spans. A new SEM for excavating large-scale underground water-sealing oil storage caverns and protecting groundwater level is proposed. The method is applied to practice successfully and the excavation characteristics were studied using monitoring datasets. Through finite element simulations, the differences between the proposed method and three-bench three-step method were compared. The influence of the section shape, bench division, and face-advancing sequences on the deformation characteristics observed in multi-step excavation was analyzed. The results showed that the maximum deformation of the excavation face was approximately 4–5 mm, and the maximum deformation rate of surrounding rock was approximately 0.8 mm/day. At 20 days after excavation, although the deformation characteristics of surrounding rock were stable, internal displacement would continue for a long time. The standard circular arch and one-step arching were useful for settlement control, and the middle drift facilitated geological forecast and water exploration. However, the more complex the bench division of the arch, the more noticeable is the stress concentration.