Abstract
A super-span tunnel that has the characteristics of a large excavation area, a small high-span ratio and a significant spatial effect exhibits a complex mechanical response during the excavation process. In this paper, taking the Badaling Great Wall station in Beijing, China as the engineering background, a case study of field monitoring a super-span tunnel has been presented. A typical monitoring section was selected in the super-span transition section of the tunnel and the deformation and forces of both the surrounding rock and the support structures were systematically monitored. The dynamic evolution and the spatial distribution characteristics of the monitoring data, including the internal displacement of the surrounding rock, the tunnel displacement, the contact pressure between the surrounding rock and the primary supports, the contact pressure between the primary and secondary supports, the axial forces in the bolts and cables, the internal forces in both the steel arches and the secondary supports and the internal stresses of the surrounding rock, were analyzed. The results of the monitoring and the analyses have shown that the deformation and the forces acting on both the surrounding rock and the tunnel’s lining are directly related to the construction procedures, the geological conditions and the locations in the super-span tunnel. According to the results, a few suggestions to improve the construction of the tunnel have been proposed.
Highlights
As the country’s economy had developed, the construction of tunnels in China has entered an era of rapid development [1,2]
When monitoring the contact pressure between the surrounding rock and the primary supports, the steel supports were used to cells placeon the pressure cells on a relatively flat surface the steel supports were used to place the pressure a relatively flat surface of the surrounding primary supports, the steel supports were used to place the pressure cells on a relatively flat surface of the surrounding rock, and the end of these were welded to the four bar lattice girders
It can be seen that the arch settlement and the horizontal convergence both increased sharply in the days; deformation slowed down and reached aconvergence staged steady state
Summary
As the country’s economy had developed, the construction of tunnels in China has entered an era of rapid development [1,2]. More and more super-span tunnels have been proposed in the fields of water conservancy, transportation and municipal engineering [3,4,5]. Over the past 30 years, Japan, South Korea and some European countries have accumulated significant experience in constructing super-span tunnels [6]. Designing the support structures, selecting the excavation methods and studying the stability of the surrounding rock of super-span tunnels are widely considered by scholars
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