ABSTRACT
Dongao Tunnel underwent the strata near the collision belt of the Eurasian Plate and the Philippine Sea Plate. The excavated geological formations suffered from deformation caused not only by the global tectonics, but also by local deep-seated gravitational slope movements (DSGS), resulting in different tunneling features. The ground deformed by DSGS exhibits open fractures between rock blocks, with infilling gouge. During initial excavation stage, rock wedges were displaced with various magnitudes around tunnel perimeter. Although cave-in due to falling of rock wedges was considered a possibility, the excavated face was generally stable. Tunneling encountered also a tectonically squeezing ground. The crew suffered from multiple severe face instabilities and squeezing problems. The responses of tunnel surrounding rock after excavation are investigated. Some innovative approaches for construction management are also introduced, including bidding strategy for contractor selection, integrated predictions on multi-temporal geological data at different scales, risk management and timely notification system.
