Shield Tunneling Technologies in Japan

7/28/2019 Shield Tunneling Technologies in Japan

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Underground Space Use: Analysis of the Past and Lessons for the Future Erdem & Solak (eds) 2005 Taylor & Francis Group, London, ISBN 04 1537 452 9

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1 OUTLINE OF THE ASSOCIATION

In recent years, use of underground spaces has beenessential to the construction of urban infrastructure.Shield tunneling methods have been gaining increasedimportance as a means of creating underground spaces.

The Shield Tunneling Association of Japan wasestablished in 1999, and its membership consists of 97companies including leading general contractors, TBMand lining segment manufacturers. It has registered 14

reliable, time-tested and state-of-the-art shield tunnel-ing technologies and methods. It has been collectingand organizing management, and thereby helping applyspecific methods and enhancing and promoting shieldtunneling technologies.

2 GENERAL

In 1939, shield tunneling was used successfully forthe first time to construct a circular railway tunnel inJapan. In the 1960s, shield tunneling began to be used

for various infrastructure projects in urban areas, andthe open shield method had its heyday until the 1980s.The period from 1980 to 1990 saw a transition from

open TBM to closed TBM such as earth pressure bal-ance shield machines developed in Japan. At present,98 percent of TBM machines used in Japan are closedtype. During the peak period in the 1980s, as many as300 contracts were awarded each year for shield tunnel-ing projects, and marked progress was made in infra-structure development.

Today, although the number of shield tunnelingcontracts awarded each year declined to around 150,the contract requirement is getting tougher such as deeptunnel under 1MPa water pressure, highway tunnel of16 m diameter, long distance drive (9km) for trans

Tokyo Bay tunnel, and increase of sections of rectan-gle and multi-circles. One of examples is shown inFigure 1.

STA is providing technical support to the challeng-ing projects with the registered 14 shield tunnelingmethods, and contributing to the development ofJapans shield tunneling technology.

3 FOURTEEN SHIELD TUNNELINGMETHODS

The 14 shield tunneling methods are registered to theShield Tunneling Association of Japan and the detailsof each method are classified into tunneling technol-ogy, multiface, non-circular, special technique,and lining technologies; and described as followswith figures for each.

Shield tunneling technologies in Japan

T. Goto, T. Masaka, K. Miki & S. TakakuShield Tunneling Association of Japan, Tokyo, Japan

ABSTRACT: The Shield Tunneling Association of Japan, STA, was established in 1999, and its membershipconsists of 97 companies including leading general contractors, TBM and lining segment manufacturers.Fourteen proven and reliable shield tunneling methods have been registered with the association to date, and theassociation is helping to apply these shield tunneling methods to various projects and promoting widespread useof those methods. This paper introduces the history of shield tunneling methods in Japan and some of the latestshield tunneling technologies, focusing on the registered 14 shield tunneling methods.

Completion year

Length,m

TEPCO

Trans Tokyo Bay

KEPCO

Gakuen Toyosaki

KEPCO

Gakuen Toyosaki

Nippa Suehiro MainTEPCO Ageo

Imaigawa Reservoir

Trans Tokyo BayHighway

KozukueMain

NTT Edogawa

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

1990 1995 2000 2005

Figure 1. Example of long distance tunnel.


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3.1 Tunneling technologies

3.1.1 DK shield methodThe DK Shield Method controls muddy soil pressurefor tunnel excavation in three phases to minimize dis-turbance to the ground.

Mud making agent is injected into soil excavated bya cutter. The excavated soil is then kneaded forcefullywith the agent using kneading blades and changed tomuddy soil with plastic fluidity and impermeability.

Kneading chamber and screw conveyor are filledwith muddy soil. Then, muddy soil is pressed by thethrust of a jack to resist groundwater pressure and earth

pressure, providing face stability.Muddy soil pressure is constantly monitored using

pressure gauges attached to the bulkhead. Shielddriving is controlled by changes in the rate of shieldadvance and the rotational speed of the screw conveyor

so that muddy soil pressure becomes equivalent to thetotal of earth pressure at rest and water pressure.It was experimented under water pressure of 0.7 MPa

and concluded that it can be applied in undergroundas deep as 50m.

3.1.2 Rheological foam shield tunnelingmethod

The Rheological Foam Shield Tunneling Method is toexcavate a tunnel while injecting foams into the faceand the chamber. The foams are generated by specialfoaming agent. The tiny foams with properties similarto those of shaving cream improve the fluidity andthe watertightness of excavated soil. Foams can also

prevent the soil from sticking inside of the chamber.This enables smooth tunnel driving while maintainingface stability. In addition, the removed soil with foamscan be defoamed and put back to the state as beforefoam injection. Then excavated soil can be easilytransported and disposed of. Thus, the method alsohas economic merit.

The Rheological Foam Shield Tunneling Methodhas been adopted on 404 projects, constructing a totallength of 412km as of April 2004.

3.1.3 Chemical plug shield methodAn additive and the main chemical agent, CP-M, aremixed with the excavated soil in the chamber. Then,the assistant chemical agent, CP-S, is injected into thescrew conveyor to create a cut-off plug from improved

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Figure 2. DK Shield Method.

Figure 3. Rheological foam shield tunneling method.

Figure 4. Chemical plug shield method.


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soil. This enables safe and accurate excavation in water-bearing gravelly soil under high water pressure, up to1.0MPa, while controlling face pressure and preventingface collapse due to blow and other soil disturbances.

The CP-M is added to conventional EPBs additiveat the plant. The plant for the CP-S may be located inthe tunnel. The excavated soil mixed with CP-M ismixed with CP-S and agitated in the screw conveyer,and rapidly changed into improved soil to form thecut-off plug.

3.2 Multiface

3.2.1 Horizontal and vertical variation shieldmethod

Cross section can be changed continuously from hor-izontal to vertical multi-circular shape or vice versa.The cross articulation system enables free control of

machine steering and orientation, and continuouschange of multi-circular cross section from horizontalto vertical alignment or vice versa.

The cross articulation system articulates multiplefront bodies of a shield machine in reciprocal directionsand make respective bodies advance in different direc-tions. The system enables shield machine to generaterotating forces and advance so that the tunnel spirals.

The machine can be divided. Therefore tunnel canbe separated without intermediate shaft.

3.2.2 Multi-circular face shield methodThe Multi-circular Face Shield Method places 2 or 3cutter heads attached to shield machines in such away that one locates ahead of others and overlapseach other. Connecting double or triple circular sec-tions, or sections of different cross sections vertically

or horizontally could offer tunnels of diverse crosssection other than a circular section.

This enables simultaneous construction of upperand lower tunnels at a site with limited land under anarrow road by vertically connecting tunnel cross sec-tions occupying a small area. Even in cases underrestrictions on vertical space due to existing structures,a multi-circular-face shield method using horizontallyconnected cross sections can be adopted.

Tunnel cross sections fit for the construction con-dition or tunnel use can be provided efficiently.

3.2.3 DOT tunneling methodThe DOT Tunneling Method is applied for an earth

pressure balance shield machine with interlockingspoke-equipped multiple cutters that are positioned inthe same plane to construct tunnels of double or triplecross sections.Adjacent cutters rotate in the opposite

directions to avoid touching or smashing one anotherand are thus controlled synchronously.

Rolling of the shield machine is controlled bycomponent force of thrusting jack by shifting alongthe circumference of the machine, and rolling control

jacks placed on the longer sides of the machine.The DOT shield machine is equipped with

cantilever-arm type erector to erect joint and panelsegments, so it provides wide working space.

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Figure 5. Horizontal and vertical variation shield method.

Figure 6. Multi-circular face shield method.

Figure 7. DOT tunneling method.


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The method provides a more reasonable shape

with smaller unnecessary space in the cross section ofrailway and highway tunnels than circular shield tun-neling methods.

3.3 Non-circular

3.3.1 DPLEX shield methodSupporting the cutter frame eccentrically at the ends ofmultiple crank shafts, and rotating the shafts in the samedirection cause the cutter to move in a circle along theinside perimeter of tunnel cross section and create across section with a shape similar to the cutter. It meansthat this method creates tunnels of any cross section.

To stabilize the face, the EPB method, which hasbeen adopted for circular shield machines and proofedhighly reliable, is basically employed.

The cross-roof bit unique to this method enablescutting in all directions with the rake and relief angles

being equal to each other.A cutter with short turning radius requires low

torque at the cutterhead. Multiple drive motors can beintegrated into a compact unit. Thus, the shield tun-neling machine can be assembled, dismantled andtransported easily. The advantage is greater for largershield machines.

A cutter with short turning radius means short bitsliding distance and reduces bit wear. Thus, tunnelscan be excavated the length about three times that byconventional machines.

The cutterhead drive motor is small enough toenable full-face soil stabilization from within the shieldmachine. Soil in curved sections or in the vicinity ofthe tunnel can be stabilized from within the machine.

3.3.2 Wagging Cutter Shield MethodWagging Cutter Shield Method enables to excavatevarious cross sections such as circular, multi-circularand rectangular sections by wagging cutter.

Cutters are wagged by reciprocating motion ofhydraulic jacks. Thus, the driving mechanism is simple

and the weight and length of the tunneling machinecan be reduced.

The rotation of the cutters and the expansion andcontraction of overcutters are automatically controlledto enable accurate excavation of corners of the cuttingface in case of non-circular shape.

Long stroke overcutters, essential to the non-circularwagging cutter shield method, are required to havehigher durability and reliability than ordinary cutters.The newly developed high-performance spike bit iscapable of penetrating and cutting the earth when theovercutter is expanded or contracted, and before andafter the cutterhead is wagged.

3.3.3 JIYU-DANMEN shield methodOne of the major features of the JIYU-DAMMENShield Tunneling Method is its capability of excavatingtunnels with various cross-sectional shapes such asoval, horseshoe and rectangle.

Adopting planetary cutters enables free selectionof the tunnel cross sections. The main cutter excavates

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Figure 8. DPLEX shield method.

Figure 9. Wagging cutter shield method.

Figure 10. JIYU-DANMEN shield method.


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the circular section at the center of the face, and themultiple planetary cutters excavate surrounding areas.

The planetary cutters, while rolling themselves,rotate along the perimeter of the rolling main cutter.The orbit of the planetary cutters can be changed freely

by adjusting the angle of swing arms attached to them.Thus, various cross sections can be easily created.

Since a horseshoe-shape, oval or rectangular cross-sectioned tunnel can be designed, a large cross-sectioned tunnel may be excavated in the ground whichis restricted in width and/or depth.

3.4 Special technique

3.4.1 Enlargement shield tunneling methodThis method allows launching the Enlargement Shieldfrom the launching base at an arbitrary location in anexisting shield tunnel and excavates the tunnel longi-tudinally to enlarge the cross section of the tunnel.

First, base for launching circumferential shield isconstructed and the circumferential shield excavates theearth around the existing tunnel. Enlargement shieldmachine is then assembled in the void created by thecircumferential shield. Enlarged tunnel is constructed

by the enlargement shield machine which runs outsidethe existing tunnel along the direction of the tunnel axis.

By the method, cross section can be enlarged for adesired length according to special need. The methodoffers even greater economy and shorter construction

period in tunneling at greater depths.

3.4.2 Rotating shield methodThe Rotating Shield Method enables to change thedirection of the tunnel driving in such a way thatspherical part with cutter rotates and launches out of it.It is called Horun. Using similar technique, for longdistance driving, cutter bits are replaced inside themachine by rotating the spherical part so that the cutterfaces inward. It is called Kurun.

In case of Horun method, excavation is carried outby a single shield machine continuously from the

ground surface first driving in the vertical direction

then in horizontal for the adit. Separate constructionof shaft by d-wall or caissons, which is necessary forconventional shield tunnel, is not required, so it con-tributes to easier construction, shorter construction

period and reduces cost.Similarly, this mechanism enables a single shield

machine to continuously excavates a tunnel, curvinghorizontally at a right angle. The machine is highlyeffective in underground spaces below congestedintersections or occupied by buried structures whereno vertical shaft can be driven for turning the shieldmachine.

In case of Kurun, the machine is effective in exca-vating long distances continuously. Cutter bits can bereplaced simply by rotating the cutter head. Themethod has eliminated ground improvement and othermeasures required by conventional methods. It isespecially beneficial for deep tunnel.

3.4.3 Mechanical shield docking method2 machines from both sides are connected mechani-cally underground without ground improvement andinflow of earth and ground water. One machine equipsinsert ring and another its receiver.

Docking and dismantling of conventional shieldmachines has been done in narrow space where theground was exposed. The Mechanical Shield Docking(MSD) Method enables steel rings to directly supportearth and water pressures, and ensures safe and reli-able work without exposing the ground.

Docking point can be selected freely without anyrestrictions of surface traffic or underground utilities.It is possible even under seabed.

The MSD Method causes neither ground settle-ment nor uplift and involves no surface work, so ithas no impacts on surface traffic or the neighboringenvironment.

The MSD Method requires no auxiliary measuresand enables easy mechanical shield docking, so it

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Figure 11. Enlargement shield tunneling method.

Figure 12. Rotating shield method.


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achieves a reduction of construction time, comparedto conventional methods.

Costs can be reduced because no auxiliary measures

for stabilizing the ground and shaft are required.

3.5 Lining technologies

3.5.1 P&PC segment lining methodThe P&PC Segment Lining provides a lining ring of

post-tensioned prestressed concrete structure by assem-bling a segmented concrete ring, giving it tension, andfastening it by inserting a prestressing single strandinto the sheath that has already been embedded in the

precast concrete segment.Because an unbonded prestressing strand with low

friction loss between the prestressing steel and sheathis used for the prestressing strand, sufficient prestresscan be introduced by applying tension to only one

position on the whole circumference. Furthermore, byusing a combined anchoring device made of cast ironthat has the tension side and fixing side integrated intoone piece (X anchor) by embedding it in the segment,the reinforcement in the segment can be simplifiedand buildability of tensioning can be improved.

3.5.2 Extruded concrete lining methodExtruded Concrete Lining Method is to construct thelining by in-situ concrete at shield tail instead of precastsegment. As the shield advances, fresh concrete isextruded and pressed considering groundwater pressure

and earth pressure in such a way that it prevents loos-ening of the surrounding earth, and the lining closelycontacted to the earth is created.

This method allows flexible choice of lining basedon the site conditions, out of reinforced concrete, non-reinforced concrete, fiber-reinforced concrete, steel-reinforced concrete and prestressed concrete.

4 CONCLUSIONS

14 shield tunneling methods registered to the STAwere outlined.

Key words describing current Japanese shield tun-neling are deep, large diameter, long driving,and various sectional shape. It is considered thatthis trend will continue. The STA intends to play arole for consultation to difficult projects using the 14registered methods.

Meanwhile Japanese shield tunneling technologieshave been mainly applied domestically. The STA con-siders the technology to be put on the world map andapplied for the prime sponsor of ITA. The authorshope that we are contacted to provide the quality ofthe Japanese shield technologies.

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Figure 13. Mechanical shield docking method.

Figure 14. P&PC segment lining method.

Figure 15. Extruded concrete lining method.

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Shield Tunneling Technologies in Japan