Chapter 3

Undersea Tunnel

Effect of Drainage and Grouting

Toshihisa Adachi1; Takeshi Tamura2    1 Geo-Research Institute, Osaka, Japan2 Kyoto University, Kyoto, Japan


The Seikan Tunnel, the world’s longest undersea tunnel, had to be constructed under the condition of severely high groundwater pressure, namely as high as 2.4 MPa, because it passes 240 m below sea level in the deepest portion. Based on prior extensive geological surveying and the construction of two inclined shafts, it became evident that the undersea tunnel could be excavated by making proper use of the cutoff method by grouting. As of early 1970, however, just after the inclined shaft of the main island section was completed, some theoretical problems related to the ...

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