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Tunnelling starts on Hiroshima Expressway Line 5

Work on the 1.8km tunnel on Expressway Line 5 in Horoshima, Japan has got underway after the tunnel boring machine (TBM) was brought onto site in small pieces to allow assembly on the 30m wide by 60m long launch site and meet transportation limits within the city.

Joint venture contractor Obayashi-Taisei-Kosei will use the 13.7m diameter Robbins slurry TBM to drive a 1.1km section of the tunnel which is set to relieve traffic congestion in Hiroshima and connectivity with the city’s airport.

The project is the first in Japan to use a TBM made by an overseas manufacturer but was selected to manage the hard rock conditions expected on the project.

“There is a lot of hard rock in Hiroshima and Robbins has a lot of experience boring hard rock,” said Obayashi deputy project manager Ryota Akai.

The machine is expected to encounter granite with rock strengths up to 130MPa UCS and the project tean has said that it intends to change the cutter discs 10 times during the 1.1km drive. Groundwater pressures of up to 13bar are anticipated and the machine has been designed to operate in up to 20bar.

Those involved in the project have said that they are interested to see what effect this project will have on how slurry TBMs are used in the future.

The tunnel is expected to be completed in 2020.

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