Developed in Japan, the URUP (Ultra Rapid Under Pass) method is being hailed as an epoch-making shield tunneling technique, enabling rapid construction of underpasses, even in urban centres with high concentrations of roads, utilities and urban infrastructures.

This new technology launches the shield TBM directly from ground level, excavates the tunnel section with shallow overburden and finally arrives back at ground level. This enables elimination of the vertical shafts required for launching and arrival used by the conventional shield tunnelling method, which greatly shortens the construction period.

As a result, the URUP method reduces the impact on the environment by reducing the amount of excavated soil, in turn reducing the number of construction vehicles needed and decreasing carbon dioxide emissions.

The URUP method was first applied in Japan on the Central Circular Route – Shinagawa Line tunnel construction project in the Oi area of Tokyo, Japan, and arrived successfully back at ground level in May 2011.

Project overview
The Central Circular Route of the Metropolitan Expressway is a circular road located at a radius of approximately 8km from the center of Tokyo with a total length of 47km. The Shinagawa Line forms the southern portion of this Central Circular Route, and consists mainly of a 9.4kmlong tunnel structure that connects the Bay Shore Line and the Route Three Shibuya Line. Construction is currently underway in order to address the social need to reduce the chronic traffic congestion in the centre of Tokyo. The Central Circular Route is being executed as a joint venture between the Tokyo Metropolitan Government and the Metropolitan Expressway Company, and aims for completion in 2013. Of the various sections, the Central Circular Route – Shinagawa Line Oi area tunnel is a construction project commissioned by the Tokyo Metropolitan Government.

Adoption of the URUP method
The construction area contains important structures such as large drainage canals and electrical power cable tunnels. In the initial planning stage it is assumed that the conventional cut and cover tunnel method will be used, and there are serious concerns about adverse impacts to these important structures due to ground deformation as a result of large-scale excavation work in the soft ground. To address these concerns, the project is commissioned as a design-build contract using a technical proposal-type comprehensive evaluation bid system.

The URUP method receives high marks and is adopted for the following reasons:

Construction of the vast majority of the route by shield tunnelling minimises the cut and cover tunnel section, which minimises the impact on nearby structures and infrastructure;

Continuous execution by a single TBM shortens the construction period;

The amount of excavated soil can be vastly reduced compared to the cut and cover tunnelling method;

Points two and three minimise the environmental impact by vastly reducing carbon dioxide emissions.

Launching and receiving at ground level
This construction project uses a largesection TBM with a shield outer diameter of 13.6m to construct a two-lane road tunnel. There are many technical issues using this type of large-section TBM in soft ground, as is found in coastal regions, when launching and arriving at ground level with minimal overburden.

However, the shield tunneling technology developed by contractor Obayashi for Japan’s soft alluvial ground that contains much groundwater is able to overcome these issues.

The Ohashi-bound tunnel was constructed first, and marked the first launch of a TBM at ground level in Japan. The TBM arrived at the Oi-kita Ventilation Station after an excavation period of six months, without significant impact on the surrounding ground. The TBM was then rotated, lifted up, and re-launched from the Oi-kita Ventilation Station to construct the Oi-bound tunnel, arriving successfully back at ground level in approximately three months.

The URUP method developed for rapid construction of underpasses is judged capable of solving the various issues facing this tunnel construction project, and realised the first successful ground level launching and arrival in Japan.

Since receiving the order for this construction project, the URUP method has also been selected for three other construction projects in Japan, and construction is currently underway.

It is hoped that in future, the TBM ground level launching and arrival URUP method will be used not only in Japan, but also around the world.

Figure 1, The Shinagawa project is part of Toyko’s Central Circular Expressway that runs on an 8km radius round the city The dramatic arrival of the URUP TBM at surface-level reception area in May this year Figure 2, from launch the TBM descends at a six per cent gradient, reaching a maximum 25m depth