Technical tasks for Tokyo Bay Crossing

This article describes a number of technical aspects of the 18 kilometer-long undersea tunnel excavation work currently being conducted in Japan’s Tokyo Bay. The tunnel, the construction of which is being conducted by a power company, will house a liquefied natural gas (LNG) pipe. Authors provide a number of features of the excavation associated with its risk including time management, hydrostatic pressure, and geological predictions. As the tunnel is only 3.6 meters in diameter, cutter changes for the excavation equipment would be time consuming and costly and so operators implemented methods to allow for a drive uninterrupted by equipment changes. This, alongside an efficient segment design, led to an advance rate of about 500 meters per month for the excavation. Difficulties with coordinating the docking of the two tunnel boring machines (TBM) at the center of the excavation, given the high hydrostatic pressure of the project, are also discussed.