Download - One Pass and Two Pass Tunnel Lining

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One-pass and Two-pass Precast Segmental Linings

Wern-ping (Nick) Chen

Jacobs

UT Austin Seminar, April 4, 2007

Applicable to:Tunnel Boring Machine (TBM) tunneling

Not for:Hand mining, such as drilled and blast or excavation

by roadheader or other mechanized means

Presentation starts from big questions and narrows down to details

Outline

1. Definitions2. Factors that drive the use of segmental

lining3. Tunnel alignments4. Rationale for choosing one or the other5. Types of precast segmental linings/Material6. Geometries7. Segment joints8. Segment construction tolerance9. Design/Modeling10. Construction considerations11. References12. Q/A

1. Definitions

Primary/initial lining

• The ground support installed immediately after the excavation

• It is a temporary structure for safety and operation during tunneling

• Normally in associated with hard rock tunneling

• Examples are rock dowels, steel set, or shotcrete

1. Definitions

Secondary/final lining

• Tunnel support or lining installed following and independent of excavation to satisfy user/function requirement

• Normally it is cast-in-place concrete

1. Definitions

One-pass lining

• Lining used as both initial support and final lining of a tunnel; normally it is precast segmental lining

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1. Definitions

Two-pass lining

• With primary/initial support installed as temporary ground support and followed by an in-situ final concrete lining

1. Definitions

Two-pass Segmental lining

• Use segmental lining as initial ground support and cast-in-place (CIP) concrete as final tunnel lining

1. Definitions

TBM Shield/Segment

TBM Shield/

Segment, Open Face, Single Shield

1. Cutterhead 2. Shield 3. Articulation (option) 4.Thrust ram5. Segment erector 6. Muck extraction conveyor 7. Muck transfer Conveyor8. Gathering arm 9. Muck hopper 10. Motor11. Tailskin articulation (option) 12. Thrust ring

Schematic Earth Pressure Balance Machine (EPBM)

Schematic Slurry Shield Machine

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• The family of open TBMs is developed for excavating in rock.• The thrusting force is obtained by reacting on the grippers.• The head is equipped with cutting disks.

1. Cutter head 2. Cutter head shield 3. Erector to place rib and mesh 4. Inner kelly5. Outer kelly in two positions with grippers and telescope jacks 6. Push jacks 7. Cutter head drive8. Rear support 9. Belt conveyer 10. Roof bolting drill 11. Probe drill

Main Beam TBM

1. Definitions

Open Gripper TBMs

2. Factors that drive the use of

segmental lining

• Ground stability during tunneling1. Soft ground tunneling2. Adverse geological condition in hard rock

tunneling; such as in laminated shale, embedded with clay

• Construction schedule – pending on the contractor, the construction schedule may be reduced

• Potential of excessive groundwater infiltrationNotes:• To be cost effective of employing a TBM, the length of the tunnel shall

be roughly greater than 1.2 miles (2 Kilometer) long• Generally speaking, the cost of a two-pass lining is lower than the one-

pass segmental lining

Case Study - Upper Rouge Tunnel ProjectLimy Shale – Fissile (disking) behavior; 30 ft ID


segmental lining


segmental lining

URT case study

• Original design – Rock dowel and steel rib as initial ground support with CIP concrete final lining

• Final design – Revised to one-pass or two-pass segmental lining

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URT – Shallow cover tunnel in Antrim Shale

3. Tunnel alignments

804

3007

40010

Minimum Radius of curvature in meters

Diameter of TBM (D) in meters

• Horizontal – public right of way; geological features; 3rd party issues (transportation and muck handling); distance/function

• Vertical – cover above tunnel crown; 1 to 2 D, pending on ground condition (design issue); function/operation; geological condition

• Radius of curvature of tunnel

4. Rationale for choosing one or the other

One-pass Segment Advantages:

• Smaller excavation diameter• Better concrete quality control (precast)• May shorten tunnel total construction schedule (but longer mucking duration)

• Robust – designed for the worst ground condition• Less water treatment required (TSS &Ph)


One-pass Segment Disadvantages

• Higher cost• Tight alignment tolerance/control• Difficult to repair• Difficult interface design and construction• Relatively delayed initial support


One-pass Segment Disadvantages

• Quality of installed bolted/gasketed system

• Tight segment construction & installation tolerance

• Need to patch bolt pockets and caulking groves (water/wastewater tunnel)

• Segment flotation during construction• Bolt corrosion (water/wastewater tunnel)• Design consideration for internal pressure at gaskets (water/wastewater tunnel)

• Maintenance

Radial Joint Detail

Gasket

Precast

Segment

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Two-pass Segment Advantages

• Robust initial ground support• Easier alignment control• Less joints in final lining• Easier interface design and construction Pattern Dowels


Two-pass Segment Advantages

• Less stringent construction tolerance; easy for erecting

• Easier alignment control• Highest TBM production rate


Two-pass Segment Disadvantages

• High cost if not using “junk” segment

• Design the worst ground condition for initial support ($)

• Few, about four (4) in the US, contractors have done junk segment

• The largest expanded segment in the US is NBC of 26’ ID tunnel

• Required more contact grout

URT South Tunnel Cost Analysis

0.8

1

1.2

1.4

1.6

1.8

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Two-pass - Dowels

& Rib

Two-pass -

ExpandedSegment

One-pass segment

Two-pass Rib only

• South Tunnel Baseline - 30-ft ID; 19,000 ft long; 20% steel rib + 6” shotcrete ; 20% 16’ pattern dowels with mesh; 12’ dowels and mesh for the rest of the tunnel

5. Types of precast segmental

linings/Material

Cross Section of Segments

(RC/FRC)


linings/Material

• Selection of segment type to suit the tunnel usage, ground condition, construction methods, and cost.

• For present time in US, concrete segment is the most popular one (highest compression capacity, but is the heaviest for handling)

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linings/Material

Segment Components


linings/Material

• As light (thin) as possible

• High strength concrete (> 6,000 psi) to accommodate shear force

• Low W/C ration (>0.4; 0.35 is normal); Adding silica film or fly ash, as cementitious replacement to Portland cement, to reduce permeability; however, with the consequence of excessive spalling in a fire event

• Small rebar cover to avoid spalling and chipping during erection (1 to 11/2” cover)

• Consider fiber to prevent cracking

5. Types of precast segmental linings/Material

Spalling of joints

Cracking and splaaing during erection

5. Types of precast segmental linings/Material

Welding a segment cage for a large diameter highway tunnel

Segment cage for a large diameter highway tunnel

6. Geometries

Cross Section

Side View

6. Geometries

K segment inserted in radial direction

K segment inserted in longitudinal direction

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6. Geometries

• αr = θk /2 + θω• θω - determined based on workability and design to transmit thrust; as small as possible; it is about 2 -5o; 3o is recommended

Segment inserted in radial direction

6. Geometries

• αl - based on construction consideration; the length of the shield; and the length of the segment; normally from 17 -20o

• αl = 0o

Segment inserted in longitudinal direction

Section a-a

6. Geometries

• Shape and width of segments normally based on handling and transportation considerations

• The thickness is normally determined from design requirements

6. Geometries

Shape and dimensions of steel segment (in mm)

6. Geometries

Shape and dimensions of concrete segment (in mm)

6. Geometries

Case 1 - key segment inserted in radial direction

Thickness is based on security load case

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6. Geometries 6. Geometries

Case 2 - key segment inserted in longitudinal direction


• Tapered ring – to accommodate curved tunnel alignment/or alignment adjustment


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7. Segment Joints

Radial Joints

Circumferential Joints

7. Segment Joints

Curve bolt (out of date)

Dowell

Straight bolt and sleeve

Shear Cone

7. Segment Joints

Dowell

Connection by drifting

7. Segment Joints

Radial joint by bolt and sleeve

Circumferential joint by dowel

7. Segment Joints

Radial joint by rod

7. Segment Joints

Circumferential joint by cone

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7. Segment Joints – Gasket Seal

Elastomeric gasket


T configuration testing

Typical pressure curve for a given displacement

Typical load deflection curve


• The selected gasket must meet watertightness rating and tolerance specified

8. Segment Construction Tolerance

8. Segment Construction Tolerance 8. Segment Construction Tolerance

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8. Segment Construction Tolerance 8. Segment Construction Tolerance

Sample ring built (normally without gasket)

9. Design/Modeling – Beam/FEM

Solid beam with full or partial bending rigidity

Ring with hinges Ring with shear and

rotational springs

9. Design/Modeling

Radial joint model:• Empirical formula by Allan Muir-Wood (1975) -homogenous rigid ring by reducing the bending

• I = IS + In • (4 / m)²

• I … reduced area-wise moment

• IS… area-wise moment of the force transmission zone

• In… area-wise moment of complete section

• m … number of segments (small key-segment not counted)

Other joint simulations:• Radial – Janssen (1983)

• Circumferential - Gijsbers and Hordijk (1997)

9. Design/Modeling

Design Loads:• Ground load – soil, long term rock, rock wedge…

• Hydrostatic pressure

• Functional – vehicular (highway, transit), surge (water/wastewater), insert support (M&E, Utility…)

• Contact grouting pressure - > 30 psi net (offset the groundwater pressure)

• Construction loads – stacking, lifting/transportation, jacking, gasket compression…

Moment distribution because of the joints

9. Design/Modeling

Stacking load

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9. Design/Modeling – construction loads

Lifting load


Contact grout

Lift/Grout socket


Ring erector


Jacking load


EPDM (Ethylene Propylene Diene Monomer) gasket compression

10. Construction Considerations –Work Shaft

• Work shafts – shaft size to accommodate TBM access and exist, specifically considering the shield size and its interaction with vent duct, convey belt, and other utilities in the shaft during construction.

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10. Construction Considerations –Work Shaft

Length of tail section

Cutter outside diameter (mm)

L/D

Length (L) to Diameter (D) Ratio

10. Construction Considerations –

Work Shaft

10. Construction Considerations –lining placement

Lifting lug

Match Marks Segment ID

10. Construction Considerations –lining match mark


Contact Grout

RemovableLifting Insert

Grout Tube

Non Return Valve

Grouting Criteria – by refusal or by volume


Contact Grout

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Tunnel Break-in

Mostly required in soft ground tunnelling


Tunnel Break-in (launching pit and cradle)

Front/Middle/Tail shieldswith JackingFrame

10. Construction Considerations –Break-in, TBM Jacking Frame

TBM Tail Initial Lining

10. Construction Considerations –Break-in, TBM Jacking Frame


Tunnel Break-in (w/o ground modification)


Tunnel Break-out

Mostly required in soft ground tunnelling

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Receiving Pit


Tunnel Break-out


Tunnel Break-out


Tunnel Break-out


Tunnel Break-out


Tunnel Break-out


Tunnel Break-out (w/o ground modification)

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Tunnel Break-out (w/o ground modification)

10. Construction Considerations

• Obstructions – headache to the shield tunneling in soft ground; identified and removed as soon as possible or baselined

• Contract documents

• Specifications – GC; DRB, VECP, EBD, Division 1, technical specifications, measurement and payment

• Drawings

• GBR – baseline for DSC

• GDR

• Alternative Bid concept

11. Reference

1. Design Philosophy of Concrete Linings for tunnels in soft soils by C.B.M.

Blom, 2002.

2. Gijsberg, F.B.J., Hordijk, D.A., 1997, “Experimenteel onderzoek naar het

afschuifgedrag von ringvoegen”,TNO-rapport COB K111

3. ITA Guidelines for the Design of Tunnels, in Tunnelling and Underground

Space Technology, 1988

4. ITA Guidelines for the Design of Shield Tunnel Lining, in Tunnelling and

Underground Space Technology, 2000

5. Janssen, P., 1983, "Tragverhalten von Tunnelausbauten mit

Gelenktübbings", Report-No. 83-41 University of Department of civil

engineering, Institute for structural analysis.

6. Japan Society of Civil Engineer 1996. Japanese Standard for Shield

Tunneling.

7. Muir Wood, A.M., 1975, "The circular tunnel in elastic ground",

Géotechnique 25(1)

8. Tunnel Boring Machines, Trends in Design & Construction of Mechanized

Tunnelling. 1996

9. Specification and Guidelines for the use of Specialist Products in

Mechanized Tunnelling (TBM) in Soft Ground and Hard Rock, EFNARC,

April 2005.

Q and A

[email protected]