Hiroshima Heavyweight: Slurry Tunneling in Japan’s Hard Rock

Credit/Quelle: Hiroshima Expressway Public Corporation

1 | Japan’s Hiroshima Expressway Line 5 is designed to improve access between Hiroshima Station and the national Sanyo Expressway via Hiroshima Expressway Line 1

Credit/Quelle: Hiroshima Expressway Public Corporation

Credit/Quelle: Robbins

2 | The fully assembled TBM cutterhead for the Hiroshima Expressway Line 5 tunnel excavation

Credit/Quelle: Robbins

3 | The custom-designed Hiroshima Slurry Shield TBM with cutterhead for hard rock excavation and robust single shield structure to support continuous and nearly settlement-free advance

Credit/Quelle: Robbins

4 + 5 | On the left: Segment erector at installation of steel segments in the start-up tunnel; on the right: Novel pick-up mechanism (arrow) for heavy segments

Credit/Quelle: Robbins

6 | With increasing hydrostatic pressures, the force required to close the segment gasket becomes larger. The Hiroshima segments require approximately two times a normal compression load as the segments are fitted with both EPDM and hydrophilic seals

Credit/Quelle: Robbins

7 | The overall site layout: The alignment of the tunnel drive, indicated in pink coloured lines, is shown in the lower right. The modular slurry plant was assembled closest to the shaft and is shown in the upper right

Credit/Quelle: Robbins

8 | The cutterhead was designed and manufactured in 10 segments, which were assembled on site

Credit/Quelle: Robbins

9 | The urban jobsite next to a park is limited to 17 600 m²
(approximately 4 acres), including the slurry plant footprint

Credit/Quelle: Robbins

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,...