Tunneling Issues Regarding the Rock Tunnel-Shaft Intersection in Taiwan

Abstract

The construction of an intersection between a shaft and a rock tunnel is a three-dimensional problem, and requires more complex excavation and support method than those used in conventional two-dimensional tunnel construction, and this fact affects both design and construction. Considering examples of rock tunnelling in Taiwan, this investigation reviews the construction of intersections between shafts and tunnels and related issues. First, cases of construction are collected and reviewed, and the excavation sequences are classified. Challenges to secure construction of the intersections of shafts and tunnels are investigated, including significant scale effects of rock masses on excavations with large cross sections, construction difficulties that are caused by the complicated arrangement of underground excavations, difficulties in controlling rock deformation near the intersections, and groundwater ingress. Strategies and countermeasures applied to overcome these difficulties are introduced with reference to recent projects, and their effectiveness is investigated. Finally, the state-of-the-art design and construction of intersections between shafts and tunnels in Taiwan are presented.