ABSTRACT
The project is a tunnel construction that connects to the highway junction located in Yokohama City. The geology is mainly composed of tuffaceous sandstone to Neogene Pliocene to Quaternary Pleistocene age, and it’s depth is 7 to 14m.The construction area is planned as a tunnel structure with a length of approximately 1,200m. The construction site is located in a quiet residential area where attentions are to be paid to the preservation of the living environment. This construction site has three sections: section A to section C. Section A, which is closest to the existing junction, has four tunnels which are in proximity and in parallel to each other. Section B is divergence and confluence part where the two tunnels merge. Section B is a twin tunnel with extremely large cross section which has a width of 29.5m and a cross-sectional area of 485m2. Section B includes up to five lanes. This is one of the largest road tunnels in the world excavated using conventional tunnelling method. Section C is the shallow section where non open cut method was adopted to preserve the living environment with a minimum overburden of 3.5m. This paper describes the experience of the world’s largest tunnel excavation under the residential area, and the lessons learned from applying various modern safety management systems suitable for the large-scale tunnel excavation.
