NOVEL MATERIAL SHIELD-CUTTABLE TUNNEL-WALL SYSTEM: NOMST

NOMST is a system developed by the Nippon Steel Corp. It consists of light weight aggregate concrete reinforced with carbon/epoxy cables that serve as lateral walls for shafts used to initiate tunneling with closed type shields (bores). Shields are commonly used for tunneling in soft soil with high groundwater pressure. The tunnel is initiated through lateral shaft walls fabricated from reinforced concrete, steel sheet-piles, and soil cement with H-beam piles. Cutting through the lateral wall into the strata behind it requires that the soil immediately behind the lateral wall be improved. One of a number of techniques shown in Fig. 3.113 can be used to prevent ground loss, excessive ingress of water into the shaft or settlement of the surface. This slows down progress and is also fairly expensive. In addition, as the shield cuts through the wall, its drill heads are severely damaged by the reinforcing steel in the lateral wall, resulting in further expenses and delays in tunneling. NOMST provides a cost-efficient means of significantly reducing damage to the shield in addition to not requiring any improvement of soil strata behind the lateral wall, providing a faster and cheaper construction method.

In this system, the portion of the lateral wall through which the tunnel is to be driven is fabricated using a special grade of lightweight concrete reinforced with cables formed of carbon/epoxy rods. The section is fabricated as precast panels (Fig. 3.116). The precast sections can be used as part of a caisson (which is sunk into place), or installed into trenches excavated to the required depth. Once the panels are placed in the trenches, the trench is filled with slurry to form a wall. The shaft is the excavated on its inside face (Figs. 3.114-115).


Fig. 3.113. Soil improvement methods for shield initiation.


Fig. 3.114. Stages in the positioning of a NOMST section.


Fig. 3.115. Insertion of a NOMST panel into a shaft.


Fig. 3.116. Details of a NOMST section.

Once the shaft is excavated, the walls are built up for stability, except the area with NOMST through which the tunneling is to be initiated. In this area, a special socket is installed to serve as a positioning device for the shield head, and retains the water pressure between the socket and the lining (Fig. 3.117-118).


Fig. 3.117. Schematic showing shield and NOMST.


Fig. 3.118. View of initiation socket and shield.

To facilitate good strength and ease of cutting by the shield, a special lightweight aggregate (mesalite, limestone and/or basalt) is used with concrete mixes designed for 28-day strengths ranging from 46 N/mm2 to 86.6 N/mm2. Carbon fibers impregnated with epoxy to form 4.4 mm diameter rods are used in cables containing 37 strands with an overall diameter of 30 mm. Properties of individual rods and the cable are shown in Table 3.27.

Table 3.27
Characteristics of Carbon Fiber/Epoxy Rods and Cables

Material Form

Diameter (mm)

Cross-Sectional Area (cm2)

Tensile Strength (kN)

Elastic Modulus (kN/mm2)

Rod

37 Rod Cable

4.4

30

0.152

5.383

23.52

457.66

205.8

166.6

As shown in Fig. 3.116, the constraining reinforcement in the NOMST section is also fabricated from carbon fiber reinforced epoxy rods.

In addition to its use as a reinforcing layer in a vertical wall, NOMST systems can also be used in other configurations such as in walls of tunnels between which a connection tunnel is to be built, tunnel arches through which vertical shafts are to be constructed, and along tunnel walls from which new tunnels are to be constructed.

The system has been successfully used in over 36 projects to date (listed in Table 3.28). The first project listed, the March 1993 Nagota electric cable-pipeline, was constructed in water bearing gravel strata using a 25 cm thick NOMST panel for a shield diameter of 2,930 mm at a cutting rate of 2 mm/min through the wall,

Table 3.28
Sample Listing of NOMST Projects

Client

Project

Contractor

Shield

Condition at Shield Opening

Water

Walls

Secondary

Size

Date

 

& Site

 

Machine (Type &/or Make)

Dia. of shield (mm)

Depth at center of opening

Soil behind shaft wall

Pressure (kgf/cm2)

of Shaft

Operation

of Panels (mm)

 

The Tokyo Electric Power Co., Inc.

Nogata District Electric Cable-Pipeline

Hazama, Fujita, Dainihon-doboku

JV

Hitachi Kenki Co., Ltd.

2930

6 m

Sand and gravel layer

0.3

Mud soil wall

t=500 mm

None

B: 250

H: 250

L: 11,000

9/92

The Tokyo Electric Power Co., Inc.

District H Pipeline Works

Hazama, Okumura, Chisaki

JV

Hitachi Kenki Co., Ltd.

3540

11 m

Sand layer, Yura-kucho layer

1

SMW

f650 mm

ctc 450 mm

None

B: 250

H: 530

L: 5740

6/93

Yokohama City

Seyaiida District Drainage Main Line

Hazama, Chisaki, Katsumura, Ishida, JV

Nippon Kokan, K.K.

4180

33 m

Sand and gravel, clay layer

1.8

RC wall

t=1200 mm

None

B: 550

H: 800

L: 9935

7/93

Bureau of Sewage Works, Tokyo Prefct.

Nansa Main Line Shaft Works

Nishimatsu, Obayashi JV

IHI Co., Ltd.

1) 3930

2) 3480

3) 3680

12 m

Clay layer, Yura-kucho layer

1

SMW

f650 mm

ctc 450 mm

None

B: 300

H: 440

L: 6530

9/93

Japan Sewage Works Public Corp.

Yokohama City Suehiro Sewer Branch Line Works

Kumagai, Konoike, Koukankoji JV

Mitsubishi Heavy Industries, Ltd.

4690

67 m

Mud/stone layer

5

RC wall

t=1200 mm

None

B: 500

H: 700

L: 6300

6/93

Tokyo Prefecture Subway Construction Co., Ltd.

Subway #12 Line, Roppongi Aoyama District

Hazama, Aoki, Ito, Aizawa, Tokukura JV

Hitachi Shipbuilding & Engineering Co., Ltd.

5440 x 2

26 m

Sand layer

1.5

Mud soil wall

t=600 mm

None

B: 700

H: 480

L: 10,740

12/93

5/94

Tokyo Prefecture Subway Construction Co., Ltd.

Subway #12 Line, Shiodome Hamamatsu-cho District

Kajima, Takenaka-doboku, Nihon-kokudo, Wakashkiu, Nara JV

Kawasaki Heavy Industries, Ltd.

5440 x 2

23 m

Sand layer

2.0

Mud soil wall

t=800 mm

None

B: 520

H: 620

L: 8720

2-3/94

Japan Railway Construction Corp.

Minatomirai Chuo Station Ookagawa T Works

Taisei, Chisaki,

Goyo JV

Kawasaki Heavy Industries, Ltd.

7300 x 2

22 m

Clay layer

1.9

SMW

f650 mm

ctc 450 mm

None

B: 300

H: 500

L: 12,200

3/94

Teito Rapid Transit Authority

Eidan #7 Line, Azabu Station Project

Zenitaka,

Misubishi JV

Hitachi Shipbuilding & Engineering Co., Ltd.

6800 x 2

21 m

Sand layer

2

Steel wall

(NS-Box) t= 900 mm

None

B: 860

H: 800

L: 11,000

5-7/94

The Kansai Electric Power Co., Ltd.

Nishimatsu, Obayashi, Maeda, Okumura JV

Nishimatsu,

Obayashi, Maeda, Okumura JV

Kawasaki Heavy Industries, Ltd.

1) 7260

2) 6850

33 m

Clay and sand layer

2.4

RC wall

t=1300 mm

Max. 3 m grouting in front

B: 600

H: 900

L: 12,300

8/94

Table 3.28 (cont.)
Sample Listing of NOMST Projects

Client

Project

Contractor

Shield

Condition at Shield Opening

Water

Walls

Secondary

Size

Date

 

& Site

 

Machine (Type &/or Make)

Dia. of shield (mm)

Depth at center of opening

Soil behind shaft wall

Pressure (kgf/cm2)

of Shaft

Operation

of Panels (mm)

 

Admin. Division, Central Wholesale Market, Tokyo Prefct.

Party box culvert (#2) shaft project

Konoike-gumi

Misui Shipbuilding & Engineering Co., Ltd.

1) 3500

2) 3500

15 m

Sand layer

1.4

SMW

f650 mm

ctc 450 mm

None

B: 300

H: 500

L: 6100

11/94

The Chubu Electric Power Co., Inc.

Niinabi #7 Series Gas Pipeline Works (#5 district)

Taisei, Konoike Shinnittetsu, Toda, Fudo JV

IHI Co., Ltd.

3660

10 m

Mud-stone layer

0.8

SMW

t=900 mm

Cut off by water glass

B: 300

H: 480

L: 6170

1/95

The Chubu Electric Power Co., Inc.

Niinabi #7 Series Gas Pipeline Works (#2 district)

Sato, Asuka, Nihon-kokuda, Taiho, Sumitomo JV

IHI Co., Ltd.

4100

30 m

Clay and sand layer

2.7

Round caisson

t=2100 mm

2 m grouting in front

Rod f12.5

Rod f20

1/95

The Chubu Electric Power Co., Inc.

Nashiro Transformer Station Project

Shimizu, Kajima, Sato, Kumagai, Hazama JV

Mitsubishi Heavy Industries, Ltd.

1) 4950

2) 4950

3) 5440

18 m

26 m

26 m

Sand layer

1.8

RC wall

t=1200 mm

None

B: 615

H: 900

L: 12,300

2/95

The Chubu Electric Power Co., Inc.

Niinabi #7 Series Gas Pipeline Works (#3 district)

Shimizu, Hazama, Take-nakadoboku, Shinnittetsu, Shiraishi JV

Mitsubishi Heavy Industries, Ltd.

4100

26 m

Sand and clay layer

2.4

Round caisson

t=1800 mm

2 m grouting in front

Rod f20

3/95

Osaka Gas Co., Ltd.

Hamadera Anchorage Shield

Konoike

Komatsu, Ltd.

1) 3000

2) 3000

38 m

Sand and clay layer

3.7

RC & steel wall

t=1000 mm

5.8 m: CJG

7.9 m: CJG

B: 510

H: 580

L: 4700

2-5/

95

Osaka Gas Co., Ltd.

Bay Line Shield

Zenitaka

Hitachi Shipbuilding & Engineering Co., Ltd.

1) 3000

2) 3000

33.9 m

Sand layer

3.1

RC & steel wall

t=1000 mm

CJG machine length 5 m

Rod f12.5

Rod f20

3/95

8/95

Bureau of Transpor-tation,

Osaka City

Osaka Subway/

Tsurumi Ryokuchi Line Extension Works

Obayashi, Konoike, Sato, Okumura, Toyo JV

Hitachi Shipbuilding & Engineering Co., Ltd.

5440 x 2

23 m

Diluvial sand and clay layer

1.2

RC wall t=1200 mm

1.5 m grouting in front

B: 500

H: 750

L: 8740

5/95

The Chubu Electric Power Co., Inc.

Niinabi #7 Series Gas Pipeline Works (#6 district)

Obayashi, Kajima, Okumura, Shinnittetsu, Taihei JV

Kawasaki Heavy Industries, Ltd.

4100

23 m

Clay layer

2

Round caisson

t=2000 mm

 

Rod f12.5

5/95

Teito Rapid Transit Authority

Shiragane Ventilation Room

Dainihondo-boku

Kawasaki Heavy Industries, Ltd.

10,040

24 m

  

Mud solid wall

t=800 mm

None

B: 530

H: 700

L: 12,480

5/95

Teito Rapid Transit Authority

Saitama Express Railway Kawaguchi Motogo District Works

Sata, Morimoto JV

Kawasaki Heavy Industries, Ltd.

9700

18 m

Sandy silt layer

1.6

RC

continuous wall

t=1000 mm

None

B: 1000

H: 900

L: 11,720

5/95

The Tokyo Electric Power Co., Inc.

Loop #7 Tokai Matsubara Pipeline

Hazama, Mitsui, Toa, Toyo, Tekken JV

Kawasaki Heavy Industries, Ltd.

7270

9.8 m

Alluvial silt layer

 

SMW

f850, ctc

600 mm

None

B: 430

H: 700

L: 11,360

5/95

Bureau of Transport., Yokohama City

Express Railway #1 Line Katsuno-kuchi District Works

Misui, Kudo JV

Hitachi Kenki Co., Ltd., Nippon Kokan, K.K.

1) 7150

2) 7150

12.5 m

Clay layer

0.7

SMW f650

ctc

450 mm

None

B: 300

H: 500

L: 9800

6/95

Tokyo Gas Co., Ltd.

Tokyo Gas / Yokohama

Kumagai, Haseko, Nara JV

Kawasaki Heavy Industries, Ltd.

1) 4290

2) 2290

17 m

Mud-stone layer

 

Round caisson

t=1000 mm

 

Rod f12.5

Rod f20

6/95

Table 3.28 (cont.)
Sample Listing of NOMST Projects

Client

Project

Contractor

Shield

Condition at Shield Opening

Water

Walls

Secondary

Size

Date

 

& Site

 

Machine (Type &/or Make)

Dia. of shield (mm)

Depth at center of opening

Soil behind shaft wall

Pressure (kgf/cm2)

of Shaft

Operation

of Panels (mm)

 

Bureau of Sewage Works, Yokohama City

Matano Drainage Main Line

Hazama, Ishida, Kojaku JV

Sumitomo Heavy Industries, Ltd.

3680

15 m

Sand and gravel layer

 

Round caisson

t=600 mm

None

Rod f12.5

7-8/

95

The Chuba Electric Power Co., Inc.

Niinabi #7 Series, Diversion Channel Tunneling Works

Kajima, Nishimatsu, Maeda, Toda, Mitsui JV

Kawasaki Heavy Industries, Ltd.

8160

   

Round caisson

t=1500 mm

None

Rod f12.5

7/95

Ministry of Construction

Ministry of Construction

Kasumigaura Takahama

Taisei-kensetsu

 

1) 5810

2) 5810

32 m

Sand layer

3

Round caisson

t=1800 mm

1.5 m grouting in front

Rod f12.5

Rod f20

7-8/

95

Teito Rapid Transit Authority

Eidan #7 Line, Kiyomasako District

Hazama, Fudo JV

 

6800

28 m

Sand, gravel, clay layer

2.3

Mud solid wall

None

B: 530

H: 1000

L: 8520

8/95

The Tokyo Electric Power Co., Inc.

Sekido, Gyokou Bridge

Hazama

Sumitomo Heavy Industries, Ltd.

2830

11 m

Sand layer

0.9

PIP

1.8 m CJG in front

B: 300

H: 370

L: 4210

10/95

Kyushu Electric Power Co., Inc.

New Oita Power Plant 3-1 Series Diversion Channel Works

Asuka, Kajima, Fudo JV

Kawasaki Heavy Industries, Ltd.

1) 6000

2) 6000

11 m

Sand layer

0.8

SMW f650

ctc

450 mm

1.5 m CJG in front

B: 300

H: 500

L: 8495

11/95

10/95

Osaka Gas Co., Ltd.

Tenpozan Offshore

Obayashi, Kubagai, Fujita, Fudo JV

 

3050

56 m

Clay layer

5

Steel wall

Freeze opening

B: 558

H: 800

L: 4950

12/95

Osaka Gas Co., Ltd.

Nanko Shield

Shimizu, Kajima, Okumura, Mitsui JV

Hitachi Kenki Co., Ltd.

3000

41 m

 

3.7

RC wall

8 m CJG & grout

B: 400

H: 670

L: 9340

12/95

Japan Railway Construction Corp.

Saitama Express Railway, Araijuku Station (end point)

Mitsui, Fukuda, Mitsubishi JV

 

9700

13.3 m

Sand layer

0.9

SMW f850

ctc

600 mm

None

B: 430

H: 710

L: 12,900

12/95

Japan Railway Construction Corp.

Saitama Express Railway, Higashi Kawaguchi Station (end point)

Asuka, Wakana, Totetsu JV

 

9600

15.2 m

Clay and sand layer

1.3

SMW f850

ctc

600 mm

None

B: 430

H: 710

L: 12,110

2/96

Japan Railway Construction Corp.

Joban New Line, Nishi Ayase T Works

Dainihon, Asanuma Chisaki JV

 

10,600

12.5 m

Clay layer

1.1

SMW f850

ctc

600 mm

None

B: 430

H: 700

L: 14,300

3/96

Bureau of Sewage Works, Tokyo Prefecture

Shingashigawa Disposal Plant Pipeline #4 End Shaft Works

Obayashi, Hazama JV

 

5540

   

Round caisson

t=1500 mm

None

Rod f12.5

5/95


Published: November 1998; WTEC Hyper-Librarian