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1.3 DPLEX method
DPLEX (Developing Parallel Link Excavating) shield method was developed from 1990 with the concept of "Any type of shape". The method was presented 'Outstanding Civil Engineering Achievement Award' by Japan Society of Civil Engineers in 1996 for the members who developed the method and in 2003 for the project of Kyoto Subway. The outline of the method is as follows. (Ref. Figure-7)
Utilizing the characteristics of DK shield.
Cutter frames are arranged into any shape depending on the boring section.
Cutter frames are driven by multi rotary shafts with eccentric crank shaft rotors.
Parallel link movement occurs during rotating the cutter frame.
Figure-7 System of DPLEX
Figure-8 Example for application
Any type of shape can be bored. (Ref. Figure-8)
The segment shall be developed accordingly. (Ref. Figure-9)
The improvement of the facing soil, where necessary, is easier because the drilling work between the cutters is capable and the space behind the cutter is wide enough.
The DPLEX tunneling method has been adopted for 10 projects so far.
Figure-9 Arc-square shape segment
Figure-10 Comparison of the rotating radius of the cutter
From its special mechanism the cutter can be rotated with the small radius (Ref. Figure-10), which have made;
Small torque power of cutter (Almost 1/3 of mono axis), thereby the method would be utilized for huge section of shield tunnel.
Less abrasion of bit (Almost 1/3 of mono axis), thereby the method would be utilized to long distance boring tunnel.
The idea of the parallel link system was born from the wheel of Locomotive. (Ref. Figure-11)
Figure-11 Wheel of Locomotive
The 1st Project adopting DPLEX technology was Sewage Tunnel in Narashino Chiba in 1994. (Ref. Figure-12)
Project Name: Narashino city Kikutagawa No.2 main lineTunneling work
Client: Japan Sewage Works Agency
Machine size : Height 3.98m x Width 4.38m
Boring Distance : First half 392.4m, Return 417.2m, Total 809.6m
Over burden : 2.4 - 4.2m
Soil Type : Fine sand (N=17 - 39), loam (N=less than 1)
Life lines under the road : 3 water pipes, 1 Gas pipe, 1 communication line (Ref. Figure-13)
Figure-12 DPLEX 1st Machine H3.98mxW4.38m
Figure-13 Cross section of the tunnel