Novel Material Shield-Cuttable Tunnel-Wall System: NONMST

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