Excavation of Japan's largest shield tunnels in the heart of Tokyo Metropolitan area - the Nishi-Shinjuku Tunnel

The Metropolitan Expressway is the main transportation route in the Tokyo Metropolitan area in Japan, with an average 1.15 million vehicles and an estimated two million users per day. In order to further improve the expressway network, an additional 46 km Central Ring was planned and constructed. Part of the Central Ring is the Shinjuku Line, which is approximately 11 km long and almost entire length was constructed below ground in bored tunnel. The Nishi Shinjuku Tunnel, forming a section of the Shinjuku Line, comprises of identical twin tunnels with outside diameter of the tunnel segment is 13.0 m. Each of the tunnels was designed to cater for traffic in one direction; each with two traffic lanes and about 600 m in length. Excavation of the tunnels was carried out by a pressurised slurry shield machine with an outside diameter of 13.23 m. The excavation operation commenced from a common launching cum receiving shaft, proceeded under an existing road for about 600 m until it reached an intermediate vertical shaft. The shield machine turned 180 degrees within the vertical shaft and headed back to the common launching cum receiving shaft, completed the twin tunnels with a total length of about 1200 m. Due to the location of construction site in the middle of the city, there was limited working space on the ground level. As such most of the temporary facilities including slurry treatment plant, slurry conveying equipment, sand screening device, back grouting equipment, etc. were installed inside the common launching/receiving shaft. The intermediate vertical shaft for rotation of the shield machine is located in gravel and sand formations with high water permeability and high pore water pressure. In order to protect the wall of vertical shaft from collapsing during arrival and re-launching of the shield machine, as well as to prevent water seepage, ground treatment work was conducted by the Freezing Method. The freezing Method was selected because of its outstanding performance in sealing off underground water and ability to create a high strength ground protection. In addition, swelling effect resulting from freezing process was relatively small in gravel and sandy soil layers and therefore impact on the surrounding ground formation was limited and/or negligible. Although there were quite a number of projects involving turning of shield machines with outer diameters of less than 7 m (weight below 350 ton) previously, there was no precedence for turning of large shield machine of this scale with a weight of 3000 ton. Therefore, various type of turning methods were thoroughly reviewed and a turning method using ball-bearings (each of the steel balls was /90 mm in size) with the assistance of two numbers of 400 ton · 2100 mm hydraulic jack, which is low cost and safe to execute, was selected. The whole turning operation took four days to complete, two days for the 180 degrees turn and another two days for lateral movements before and after the rotation. Excavation of the tunnels started in September 2000 and was successfully completed as scheduled in February 2002. (A). "Reprinted with permission from Elsevier". For the covering abstract see ITRD E124500.

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  • Authors:
    • NISHIOKA, I
    • KAWASE, O
    • NAMIKAWA, K
    • ENDO, K
  • Publication Date: 2004-7

Language

  • English

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Filing Info

  • Accession Number: 01011536
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD
  • Created Date: Dec 19 2005 3:16PM