One Pass and Two Pass Tunnel Lining

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Transcript of One Pass and Two Pass Tunnel Lining

One-pass and Two-pass Precast Segmental LiningsWern-ping (Nick) Chen JacobsUT 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

Outline1. Definitions 2. Factors that drive the use of segmental lining 3. Tunnel alignments 4. Rationale for choosing one or the other 5. Types of precast segmental linings/Material 6. Geometries 7. Segment joints 8. Segment construction tolerance 9. Design/Modeling 10. Construction considerations 11. References 12. Q/A

1. DefinitionsPrimary/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. DefinitionsSecondary/final lining Tunnel support or lining installed following and independent of excavation to satisfy user/function requirement Normally it is cast-inplace concrete

1. DefinitionsOne-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. DefinitionsTwo-pass lining With primary/initial support installed as temporary ground support and followed by an insitu final concrete lining

1. DefinitionsTwo-pass Segmental liningUse segmental lining as initial ground support and cast-inplace (CIP) concrete as final tunnel lining

1. DefinitionsTBM Shield/Segment

Segment, Open Face, Single Shield

TBM Shield/

1. Cutterhead 2. Shield 3. Articulation (option) 4.Thrust ram 5. Segment erector 6. Muck extraction conveyor 7. Muck transfer Conveyor 8. Gathering arm 9. Muck hopper 10. Motor 11. Tailskin articulation (option) 12. Thrust ring

Schematic Earth Pressure Balance Machine (EPBM)

Schematic Slurry Shield Machine

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Open Gripper TBMs

1. DefinitionsMain Beam TBM 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 kelly 5. Outer kelly in two positions with grippers and telescope jacks 6. Push jacks 7. Cutter head drive 8. Rear support 9. Belt conveyer 10. Roof bolting drill 11. Probe drill

2. Factors that drive the use of segmental lining Ground stability during tunneling 1. Soft ground tunneling 2. 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 infiltration

2. Factors that drive the use of segmental liningCase Study - Upper Rouge Tunnel Project Limy Shale Fissile (disking) behavior; 30 ft ID

Notes: 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 onepass segmental lining

2. Factors that drive the use of segmental liningURT 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 Horizontal public right of way; geologicalfeatures; 3rd party issues (transportation and muck handling); distance/function

4. Rationale for choosing one or the otherOne-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)

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

Radius of curvature of tunnelDiameter of TBM (D) in meters 10 7 4 Minimum Radius of curvature in meters 400 300 80

4. Rationale for choosing one or the otherOne-pass Segment Disadvantages Higher cost Tight alignment tolerance/control Difficult to repair Difficult interface design and construction Relatively delayed initial support

4. Rationale for choosing one or the otherOne-pass Segment DisadvantagesQuality 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) MaintenanceRadial Joint Detail

Gasket Precast Segment

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4. Rationale for choosing one or the otherTwo-pass Segment Advantages Robust initial ground support Easier alignment control Less joints in final lining Easier interface design and construction

4. Rationale for choosing one or the otherTwo-pass Segment AdvantagesLess stringent construction tolerance; easy for erecting Easier alignment control Highest TBM production rate

Pattern Dowels

4. Rationale for choosing one or the otherTwo-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 grout2 1.8 1.6 1.4 1.2 1 0.8

URT South Tunnel Cost Analysis

Two-pass ExpandedSegment

Two-pass - Dowels & Rib

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

5. Types of precast segmental 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)

(RC/FRC)

Cross Section of Segments

One-pass segment

Two-pass Rib only

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5. Types of precast segmental linings/Material

5. Types of precast segmental 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

Segment Components

5. Types of precast segmentallinings/Material

5. Types of precast segmental linings/Material

Spalling of joints

Cracking and splaaing during erection

Welding a segment cage for a large diameter highway tunnel

Segment cage for a large diameter highway tunnel

6. Geometries

6. Geometries

Cross Section

Side View

K segment inserted in radial direction

K segment inserted in longitudinal direction

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6. Geometries r = k /2 + - determined based onworkability and design to transmit thrust; as small as possible; it is about 2 -5o; 3o is recommended

6. Geometries l - based on construction consideration; the length of the shield; and the length of the segment; normally from 17 -20o l = 0o

Segment inserted in radial direction

Section a-a

Segment inserted in longitudinal direction

6. Geometries Shape and width of segments normally based on handling and transportation considerations

6. GeometriesShape and dimensions of steel segment (in mm)

The thickness is normally determined from design requirements

6. GeometriesShape and dimensions of concrete segment (in mm)

6. GeometriesCase 1 - key segment inserted in radial direction

Thickness is based on security load case

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6. Geometries

6. GeometriesCase 2 - key segment inserted in longitudinal direction

6. Geometries Tapered ring to accommodate curved tunnel alignment/or alignment adjustment

6. Geometries

6. Geometries

6. Geometries

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7. Segment JointsCircumferential Joints Radial Joints

7. Segment Joints

Curve bolt (out of date)

Straight bolt and sleeve

Dowell

Shear Cone

7. Segment JointsConnection by drifting

7. Segment Joints

Dowell

Radial joint by bolt and sleeve Circumferential joint by dowel

7. Segment Joints

7. Segment Joints

Radial joint by rod

Circumferential joint by cone

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7. Segment Joints Gasket Seal

7. Segment Joints Gasket Seal

T configuration testing

Elastomeric gasket Typical pressure curve for a given displacement Typical load deflection curve

7. Segment Joints Gasket Seal 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

9. Design/ModelingRadial joint model:Empirical formula by Allan Muir-Wood (1975) homogenous rigid ring by reduci