The DPLEX shield method applied for the first time to a railway tunnel in Japan

The DPLEX shield method, developed in Japan in 1990, permits excavating tunnels of any cross-section shape. So far, a total of 10 rectangular and round tunnels have been constructed by using this method. This method employs cutter frames, each of which is eccentrically supported by multiple cranks shafts. By rotating the crankshafts in the same direction, the cutter frames perform a parallel link motion, cutting a cross section almost similar to the cutter frame shape. The present work is one in which the DPLEX shield method was employed for the first time to excavate a subway tunnel of Yokohama in Japan. The tunnel length is 884 m (452 m going and 432 m returning); the segment outside diameter, 7000 mm; the shield outside diameter, 7150 mm; the segment thickness, 300 mm; and the segment width, 1200 mm. The geology of the construction site consists mainly of alluvial clayey soil (N = 2-5) and sandy soil (N = 5-15), with a layer of gravels up to 250 mm in diameter (N = 50 or more) in the starting section. The principal specifications of the 7150 mm diameter DPLEX shield are as follows: cutter turning radius 400 mm, cutter torque 2213 kN m, and cutter speed 2 rpm. The cutter bits are a combination of cross roof bits and roof bits which are so arranged that they can cut even the tunnel portion around the projection of the injector pipes for simultaneous backfilling. The results of execution of the tunnel construction work are as follows: (1) The muddy-soil pressure balancing system was employed to stabilize the cutting face. The soil pressure used to control the excavation operation was 230-260 kPa. As a result, the amount of ground subsidence could be con trolled to 2-3 mm even in the alluvial ground of the construction site. The cutter rotations had no effect on the ground subsidence. (2) The amount of yawing and pitching due to the eccentric cutter rotations was so small that the excavation opera tion was not affected at all. (3) Regardless of the geologic features of the construction site (alluvial clayey soil, sandy soil, and gravel), good plastic fluidity could be secured by injecting mud-making agent and mixing it with excavated soil. (4) The cutter torque was about 600-700 kN m in sandy/clayey soil and about 1000-1200 kN m in gravel, each being one-third that of the conventional muddy-soil pressure balanced, single-shaft shield. (5) The amount of cutter bit wear was 0.64 mm on average. The coefficient of wear was 0.0037 mm/km, much smaller than that of the conventional shield. This is a major advantage of the DPLEX shield. (6) All the basic problems of the DPLEX shield method, such as the cutting face stability, shield position control, cutter load characteristic, and kneading blade performance, have been solved in the process of planning of the shield and by the experience in tunnel excavation using the DPLEX shield method. It is considered, therefore, that there are no problems in building tunnels 10-16 m in diameter by using the DPLEX shield method. (A) "Reprinted with permission from Elsevier". For the covering abstract see ITRD E124500.

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  • Authors:
    • SUGA, T
    • KASHIMA, Y
    • KONDO, N
  • Publication Date: 2004-7

Language

  • English

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Filing Info

  • Accession Number: 01011571
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD
  • Created Date: Dec 19 2005 3:18PM