Maintenance of engineering structures at the sea bottom of Seikan Tunnel

The Seikan Tunnel is a very long one running at 240m deep under the sea and subjected to a tremendous water pressure, while at the same time it is one which has been bored into the geology comprising a lot of faults and fragile zones. For these reasons, engineering structures at such depth of the sea call for establishment of an appropriate maintenance technology considering various data on their construction. The Japan Railway Construction Public Corporation has taken care of the Seikan Tunnel with provision of instrumentation and other services since it was opened to traffic, in an effort to grasp its features as an undersea tunnel. This paper outlines its background.