Development of upward shield method

Shield tunneling technology plays an important role in underground construction in Japan. The technology has become more sophisticated in terms of safety and range of applications and is increasingly applied to the construction of tunnels in urban areas. In the upward shield method, a dedicated shield tunneling machine is used to bore a shaft from an underground shield tunnel to the surface. Development of the method began in 1993 with the goals of eliminating the difficulty of acquiring land in densely populated urban areas and of developing a safer and more environmentally friendly tunneling method. Recent developments in the technology are aimed at constructing tunnels that are larger and more irregular in cross section, that have curves with smaller radii, and that can be constructed at greater depths. The method can be used to construct water supply and sewage systems (pipelines, and water intake and maintenance shafts), multi-purpose underground conduits (branch shafts for gas pipes and cables), railroads (ventilation, maintenance, and escape shafts, and elevator shafts at stations), roads (ventilation and escape shafts), and underground structures (physical distribution shafts.) The method can be used in cohesive soil, sandy soil, sand-gravel soil, and soft rock. It can produce shafts that are 2-4 m in diameter and approximately 50 m in depth. The important point in this method is that segments of the existing shield tunnel at the entrance opening for the upward shield machine needs to be assembled in advance by using materials that are cuttable by the shield machine. Pinch valves are used in the machine's muck discharge system. These valves consist of a rubber sleeve mounted in the muck discharge pipe. Inflating/deflating the sleeve changes the cross-sectional area of the pipe, which controls the soil pressure at the shaft face and the volume of the muck discharge. The upward shield method has several advantages. First, it minimizes the impact of the tunneling work on the surroundings, including traffic flow, by shortening the time needed for construction work on the surface. Moreover, shafts can be constructed in confined areas, and the machine can be retrieved for reuse after it arrives at the surface. This method was first applied in 2000 to a sewer construction project in which shafts of 20.3-32.8 m in depth were constructed at three locations using a single shield tunneling machine. In the sewer work, a polymer was used as an additive to facilitate the plastic flow of muck and pinch valves were adopted to discharge muck stably. As a result, soil pressures at the shaft face could be controlled satisfactorily. Displacements of the ground around the shaft were small, not more than 0.4 mm. It took approximately two months to construct the shaft at each site, of which boring the shaft by the upward shield method took one month. These records demonstrated that this shield method is promising for further applications in urban areas in Japan. (A). "Reprinted with permission from Elsevier". For the covering abstract see ITRD E124500.

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  • Authors:
    • ITO, K
    • SAKAE, T
    • HARA, S
    • ITO, H
    • HASHIMOTO, H
  • Publication Date: 2004-7

Language

  • English

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Filing Info

  • Accession Number: 01011640
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD
  • Created Date: Dec 19 2005 3:22PM