Hiroshima Heavyweight: Slurry Tunneling in
Japan’s Hard Rock

Below Hiroshima, Japan, a 13.7 m diameter Robbins Slurry TBM is making steady progress in hard rock. The TBM was assembled onsite for the Hiroshima Expressway
Line 5 project. The 1.8 km long tunnel to be built in a densely urban area in granite rock and high water pressures required a unique machine. The design of the Slurry machine was tailored for abrasive rock conditions and water pressures up to 13 bar. As of October 2020, the machine has bored over 430 m into the tunnel.

Project Background

Japan’s Hiroshima Expressway Line 5 is designed to improve access between Hiroshima Station and the national Sanyo Expressway via Hiroshima Expressway Line 1. Specifically, the new Expressway Line 5 tunnel will directly connect Hiroshima’s urban area with a major national highway network and is expected to improve access to Hiroshima Airport (Fig. 1). The 1.8 km Hiroshima Expressway Line 5 tunnel was considered for many years, but approvals were difficult to obtain. This was mainly because of subsidence and noise concerns raised from residences above the tunnel route,...

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