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1、Construction Project of a Natural Gas Transmission Pipeline in Long and Deep Tunnels in Tokyo City with new technologies1Hiroyasu Yamanouchi1. the Chuo transmission pipeline construction office Tokyo Gas Co., Ltd.Keywords: 1. pipeline construction; 2. tunnel; 3. coating1BackgroundIt was planned to c

2、onstruct a pipeline named “Chuo Line” with the length of 23.1 km in order to transport natural gas to industry areas in the northern part of Tokyo City. The pipeline was decided to pass directly through highly populated residential and commercial area in the center of Tokyo City (Figure 1), so as to

3、 minimize the pressure reduction at the end as shown in Figure 2. The pipeline had to keep proper distance from various aboveground and underground structures, and therefore the entire pipeline was decided to be installed in long tunnels with 40m depth cover on average, as shown in Figure 3.Figure 1

4、Highly populated residential and commercial areaFigure 2 Schematic diagram of the route of Chuo Line and other existing transmission pipelines designated with a red dotted line and blue solid lines, respectively.Figure 3 Vertical section view of the pipeline (red line : tunnel route)Tochigi Pref.Nor

5、thern part of Tokyo CityIbaraki Pref.“Chuo Line”Saitama Pref.Tokyo CityTokyo BayKanagawaPacificPref.OceanChiba Pref.2Design Specification and New TechnologiesThe pipeline is API 5L X-65 line pipes with mill-applied three-layer extruded polyethylene coatings. The outside diameter and wall thickness o

6、f the pipeline are 610 mm (24 inches) and 15.1mm. Annular space between the line pipes and tunnels is filled with foam mortar as an electrolyte to provide cathodic protection currents on the carrier pipes within the tunnels. Foam mortar consists of cement and organic blowing agent that is added to r

7、educe the weight of cement and enables uniform filling.A design competition was held to reach out the most suitable design and construction method for this challenge among Japanese leading contractors. Only starting point, end point, diameter of gas pipe, and gas pressure were given conditions in th

8、e request for proposal. Proposals could vary from “open-cut installation” to “deep undergroud tunnel.” Even route was at proposers choice.Comprehensive evaluation was made by scoring (1) project feasibility, (2) time and cost savings, and (3) established unique technologies and new technologies. As

9、for the “project feasibility”, considering strong environmental and safety concern of the local society, key issues for project success were minimum environmental impact, safe and low-profile structure, short-term construction period, and minimum interaction with other underground structures. The pr

10、oposal of a deep and long tunnel using high-speed slurry shield TBM excavation with new challenging excavating technologies was adopted to accomplish this new challeging project.Based on the proposal, schematic cross-sectional view of the pipeline and tunnel is shown in Figure 4. Long deep tunnels c

11、onsist of steel plate segments (L=1000 mm, W=approx. 400 mm, t=100 mm and the inside diameter is 2,000 mm (80 inches), which is the minimum diameter cross-sectional space to install pipelines .The maximum and average depths of cover are 65 m and 40 m, respectively.Several new tunneling techniques we

12、re applied for long-span high-speed tunneling and underground direct docking resulting in the reduction of construction period and cost as well as environmental impact to heavy traffic and residents. Moreover, in order to minimize the risk of external corrosion, new field joint coating system was de

13、veloped. Details of these new techniques are described in the following.Ground levelDepth of cover of40m (Ave.) and 65m (Max.)2,000mmTunnel consists of steel platesPipelineFoam mortar610mmFigure 4 Cross-sectional view of the pipeline3New Tunneling TechniquesNew tunneling boring machines (TBMs) were

14、developed in order to achieve long-span high-speed tunneling as shown in Figure 5. Figure 6 indicates three types of teeth are set on the round cutting plate at the front face of TBMs, and each type of teeth has different height. After the highest teeth is wore out, second the high teeth will start

15、to work, and thus new teeth can be obtained at the front face all the time. Long-span tunneling can then be achieved without exchanging old teeth. The maximum span of the tunnels by single new TBM is 6.3km that is the longest in Japan for the tunnels with such large diameter. Additionally, three mor

16、e remarkable new technologies were adopted in the following.Figure 5 New tunneling boring machine (TBM) ( Dual- Diameter TBM )Figure 6 Three different height of teeth at the front face of TBMs3.a Underground Docking of TBMsIt is very difficult and time-consuming to find and acquire temporary constru

17、ction site in the congested downtown Tokyo area, and private land was so costly that the number of shafts and the space of each shaft was required to reduce. To deal with this problem, underground direct docking of TBMs coming from both directions was conducted in order to connect long-span tunnels

18、without shafts. This can be done using high resolution locating system for TBMs. Soil adjacent to the docking point was compulsorily frozen in order to prevent water penetration into the tunnels during docking, as shown in Figure 7.This underground docking technology enabled that the 23.1 km-long tu

19、nnel was constructed using only two intermediate shafts, dividing the whole route into 5 tunnel sections and connecting tunnels deep underground, as shown in Figure 8 . The longest single span was 11.1 km, which consists of 6.3km and 4.8km tunnel sections excavated simultaneously in face to face dir

20、ection and connected.Figure 7 Process of direct underground TBM dockingteethTBM For 2000 tunnelTBM For 2600 tunnelcu ting plate total tunnel length 23.1kmsteel segment OD 2,260mm ID 2,000mmShinkoiwa TBM3.8kmAdachi TBM 6.3kmHorikiri TBM 4.8kmKasai TBM 3.8kmFunabori TBM4.4kmTateishi shaft ID 11.0mDP -

21、36.5mKasai shaft ID 3.0m DP -13.8mSoka shaft 6.0m x 43.5m DP -11.9mKitakasai shaft ID 10.0mDP -37.3mShinkoiwaunderground dockingLarger dia. tunnel section (OD 2,950mm ID 2,600mm) utilizing multistage launching TBMKahei undergrounddockingFigure 8 Construction plan3.b. Dealing with the limited small s

22、pace of temporary construction sitePrivate land was acquited as two intermediate tunnel shaft sites, however the each land available was small and limited in highly populated commercial area.Figure 9 indicates that high capacity waste slurry processing plant was compactly installed in each shafts ma

23、rginal space utilizing three-story deck structure with underground waste soil pit.In order to stock and deliver enough number of segments for high speed around-the-clock TBM excavation, newly developed computerized segment stock sytem was introduced as shown in Figure10.This was the key driving forc

24、e to solve complex material handling and transportation problems attributable to small tunnel shaft and temporary construction site in the middle of downtown where night delivery was not allowed.stacker crane capacity 1000 kgcontrol roomsegment rack capacity 88 pc.vibratingscreenfilter pressground l

25、evelloading and unloading platform capacity 1000 kgregulating tankwaste soil pitsegment setter capacity 1500 kglaunching shaftsegment lifter capacity 1500 kgFigure 9 double-launching tunnel shaftbatterylocomotivereceivingdeckFigure 10 Segment stock system3.c. Dual-diameter TBM and High-speed excavat

26、ing technologyHigh speed TBM excavation depends on delivery capacity of segment as well as capacity of TBM itself. The new TBM involves two different diameters of 2,000mm and 2,600mm. When a TBM starts tunneling from a shaft, a tunnel with larger diameter of 2,600mm (the outer TBM) is excavated as s

27、hown in Figure11. After 50m tunneling, a TBM with the diameter of 2,000mm (the inner TBM) launches from the outer TBM and solely continues tunneling.The wider diameter tunnel section was to accommodate double track for the segment transportation train which was designed for switching yard of the tra

28、in and temporary segment stock yard. Due to adequate space available in the vicinity of the shafts, steel plate segments can continuously and efficiently be transported using electric motor trucks within the tunnels as shown in Figure 12. Speed of tunneling is governed by the speed to transport of s

29、egments, and thus high-speed tunneling of 400 m/month on average can be achieved using new “dual-diameter” TBMs.Figure 11 Dual-diameter tunneling from a shaftFigure 12 Continuous transportation of steel plate segmentsnorm altunnel 2000m m w ide tunnel 2600m mtrucks fortransportation ofsegm entexcava

30、tionexcavationshaft4New Field Joint Coating SystemThe pipeline was installed within deep tunnels, and therefore it is impractical to excavate and repair upon the completion of construction. New field joint coating system was then developed in order to minimize the risk of external corrosion. Schemat

31、ic diagram of the new system is shown in Figure 13. New system consists of the first layer of heat-shrink sleeve (HSS) with mastic adhesive (soft) and the second layer of HSS with hotmelt adhesive (hard). HSS with mastic provides adequate adhesion between HSS and line pipes with surface pre-treatmen

32、t of grinding (not blasting). In addition, HSS with hotmelt provides excellent adhesion between HSS and mill-applied three-layer extruded polyethylene coatings. The risk of water penetration from the edge of field joint coatings is then minimized resulting in the corrosion prevention under field joi

33、nt coatings due to cathodic protection shielding. Actually, markedly high level of peel strength more than 10 kg/cm (100 N/cm) was obtained between HSS with hotmelt and mill-applied coatings.In order to maintain uniform heating without hand-held burner and stable quality in narrow tunnels, a vacuum

34、chamber with computer-controlled far infrared heating system is used for the application of both heat-shrink sleeves, as shown in Figure 14. After covering field joints and each HSS within the vacuum chamber, pressure inside the chamber is reduced to eliminate dust and condensation of water vapor, a

35、nd then HSS is heated. This vaccuum chamber requires no fire in the tunnel, contributing the safety of workers in the narrow tunnel.Plastic cover sheetHeat-shrink sleeve with hotmeltHeat-shrink sleeve with masticGirth weldMill-applied three-layer extruded polyethylene coatingsPipe wallFigure 13 New

36、field joint coating systemFigure 14 Vacuum chamber with heating system5ConclusionNew tunneling techniques enables the reduction of construction period and cost as well as environmental impact, and the construction of tunnels was successfully completed in March 2007. The high-pressure line pipes were

37、 installed in narrow tunnels, including transportation of line pipes and semi-automatic girth welding process followed by the application of new field joint coating system. The whole construction project was completed in December 2008.During the whole period, no claims on adverse effect on other underground structures, ground settlement, noise, vibration, an