Chapter 1 Tunnel and Underground Space Uses… Planning Meetings/2009/TRB Jan 0… · TRB Workshop...

TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 1&2

Parsons Brinckerhoff 1

Chapter 1 Planning

Definition of TunnelsShapes and Construction TypesAlternative AnalysisOperational and Financial PlanningTunnel Type StudyRisk Analysis and Management

Tunnel and Underground Space Uses…Transportation

Vehicular (road tunnels)Transit and rail (subway, freight, passenger rail, etc…)

Water ConveyanceWater supplyWaste water (storm, sanitary, combined sewers, CSO, etc…)

Utilities (electrical, steam, communications, etc…)

Power stations, valve chambers, substations, etc…Storage (cold storage, document storage, nuclear waste, liquid storage, oil, wine, etc…)MinesDefense and National Security projectsCommercial, residential, institutional facilities, etc…Unique projects/Applications (SMART Tunnel)

…Tunnel and Underground Space Uses Storm water Management and Road Tunnel or (SMART) Kuala Lumpur Malaysia

Definition of Road Tunnels

Road Tunnels:“Road tunnels (as defined by AASHTO Technical Committee for Tunnels (T-20)) are enclosed roadways with vehicles access that is restricted to portals regardless of type of the structure or method of construction.”

Tunnel Types Planning/ Route

Selection

Cut & Cover Tunnels

Mined/Bored Tunnels

Rock Tunneling

Water Land

Immersed Tunnels

Soft Ground Tunneling

Difficult Ground

Tunneling

SEM/NATM Tunneling



Examples of Road Tunnels

Fort McHenry Tunnel - Baltimore Highway H-3 Oahu, Hawaii

Road Tunnels

Hanging Lake Tunnel Colorado

Cumberland Gap Tunnel Kentucky/Tennessee

Tunnel ShapesRectangularCircularHorseshoe, CurvilinearOther Shapes:

Cavern shapesUnique shapes (elliptical, double-o-tube, etc…) Shafts – (circular, square, rectangular, elliptical)

Configuration dependsType of ConstructionUses

Liner and Finishes

Rectangular Tunnels

Cut and Cover and Immersed Tunnels

Rectangular Tunnels Most common for road tunnelsCut and CoverImmersed Tube Tunnels

Fort Point Channel - Boston 2nd Elizabeth River Tunnel Norfolk (cut and cover segment)

Circular Tunnels

Road tunnels Other uses:

Transit and rail tunnelsWater conveyance

Most suited for TBM construction



Circular Tunnels

Bored (mined) Tunnels

Rock Soft GroundTBM

A-86 Road Tunnel - Paris

Examples of Circular Road Tunnels

Westerschelde Tunnel - Netherland

Segment 450 mm thick

Steel Segments

Largest Bored Circular Road TunnelChongming under Yangtze River Tunnel, Shanghai – 15.43 m TBM

Horseshoe Tunnels

Horseshoe TunnelsRock Tunnel (Drill and Blast)SEM/NATM (Conventional Tunneling)Cut and CoverImmersed TunnelConventional ExcavationMechanized (Road Header)

2nd Downtown Tunnel Norfolk

Glenwood Canyon Colorado

Devil Slide Tunnel – San Francisco

L=1300m each10 Emergency Cross Passages -every 120m



Classes of Roads

AASHTO’s Policy on Geometric Design of Highways and Streets (2004) – Green BookAccommodate all vehicles sizes permitted on the roadCost Conscious

A-86 Tunnel Paris, France

Alternative AnalysisRoute StudyType Study

Cut & cover, bored, immersed tube, SEM/NATM, etc…Financial Evaluations

Capital cost and maintenance/operational costsLife cycle cost

Geological and Site ConstraintsEnvironmental Issues

SustainabilityOperational Issues

Traffic control, ventilation, fire-life safety, maintenance, etc.

Route StudySubsurface, geological, and geo-hydraulic conditionsConstructibilityLong-term environmental impactSeismicityLand use restrictions Potential air right developments Life expectancyEconomical benefits and life cycle costOperation and maintenanceSecuritySustainability

Tunnels Enhance Sustainability

Mercer Island, Seattle

Tunnel Construction TypesCut-and-CoverBored or Mined Tunnels

Rock TunnelsSoft Ground Tunnels Mechanized (TBM)Conventional (NATM/SEM, Drill and Blast)

Immersed TunnelsSpecialty (Jacked Tunnels)

Yangtze River Tunnel – Shanghai China 15.43 m Diameter

Cut and Cover Tunnels



Bored Tunnels – Soft Ground

M30 Madrid 13.45 m Diameter

Immersed Tunnels

Ft McHenry Tunnel, Baltimore

Specialty Type ConstructionStacked Drifts

Mt Baker Ridge Tunnel - Seattle

Specialty Type Construction Tunnel Jacking

Central Artery Under South Station - Boston

Design ProcessDefine Functional RequirementsPerform Surveys and Investigations Perform Environmental StudiesPrepare Tunnel Type StudyEstablish Alignment, Profile and Cross SectionEstablish Design Criteria, and perform the design various elements: preliminary and final designsConduct Risk AnalysesPrepare Construction Contract Documents including drawings, specs, cost estimates, GBR, etc…

Groundwater ControlOpen System (drained)Closed System (un-drained)

Drained waterproofing system

Un-drained waterproofing system



Fire Life Safety AspectsNFPA 502 Refuge SpaceEmergency Walkway – 3.3 ft (1m)Exits Spacing 1000 ft (300 m)Cross Passages 650 ft (200m)Fire Rating -2 hr MinimumSignageEmergency Lighting, Fire Detection (or suppression), Fire Lines, Hydrants, communications, etc…Emergency Ventilation and Control Systems Emergency Exit

Fire-Life Safety System

Emergency Alcove

Tunnel FiresRoughly one-third of all tunnel fatalities are from firesFires have the ability to quickly spread engulfing tunnelFires affect all tunnel occupantsFires require evacuation and management to prevent loss of life and structural damage Structural damage often results in tunnel closure and revenue loss.

Channel Tunnel Fire -20 cm spalledNov 96

St. Gotthard Tunnel Oct 01

Fire Heat Release Curves

Fire Heat Release CurvesThe Cellulosic Curve Hydrocarbon (HC) curve

Simulates fires in tankersThe RABT-ZTV curve (Germany)

Represents shorter duration fire Rapid rise in temperature

The RWS Curve (Netherlands) Represents 300MW fire load Trapped heat cannot easily dissipate

Tunnel Ventilation

Transverse Semi TransverseLongitudinal (jet fans)Push-PullSeccardo Nozzle

Brooklyn Battery tunnel – Transverse ventilation



Tunnel Ventilation

Typical Vane Axial FansJet Fans – Detroit Metro Airport Tunnel

Operational and Financial Planning

Traditional Funding Sources (Federal, State, Local, Bonds, etc…)Alternative Funding

Public Private Partnership (PPP)DBOM

Operational and Maintenance Cost PlanningCost Analysis and Cash FlowProject Delivery

Design-Bid-BuildDesign-Build

Procurement OptionsCompetitive Bid (low price – Lump Sum , Unit Prices)Quality Based SelectionBest and Final Offer (BAFO)Cost Plus FeeNegotiated Procurement

Chapter 2 Geometrical Configuration

Horizontal And Vertical AlignmentClearancesCross Section Elements

Geometrical Configuration

General Geometrical Requirements Horizontal and Vertical AlignmentsCross Section ClearancesCross Section ElementsAASHTO Green BookStandards by States and LocalitiesNFPA 502

Horizontal and Vertical Alignment

Maximum Effective Grade 4%Horizontal and Vertical Curves

Meet Green Book RequirementsMinimum Radius 1000 ftSuperelevation 1% to 6%

Sight and Breaking Distance Design Flood Level (500 Year Occurrence)

Minimum and Desirable Travel Clearance

Clearance Diagram using Vehicle Dynamic EnvelopesMin Vertical Clearance 14 ft

Future ResurfacingTruck Mounting the CurbMilitary Cargo

Desirable Vertical Clearance 16 ftLane Width 12 ftShoulders Minimum 0 ft to 1.5 ft

Minimum

Desirable



Modified Shoulders Modified Shoulders

Typical Cross Section Elements Travel Lanes – Shoulders - Sidewalks/CurbsTunnel Drainage Tunnel VentilationTunnel Lighting Signals and Signs Above Roadway Lanes Tunnel Utilities and PowerWater Supply Pipes for Firefighting Cabinets For Hose Reels and Fire ExtinguishersCCTV Surveillance Cameras Emergency Telephones/ Communication Equipment Monitoring Equipment Of Noxious Emissions And VisibilityEmergency Egress Illuminated Signs

Tunnel Width

Travel Lanes 12 ftFull vs Reduced ShouldersBarriers Sidewalks/Emergency Egress

Miami Port Tunnel

Tunnel Width Typical Cross Section

Cumberland Gap Tunnel



Lighting Requirements

ANSI/IESNA RP 22 “Recommended Practice for Tunnel Lighting”Black Hole Effect

PortalsLocation and OrientationFunctionality

Dividing wallsFlood LevelTraffic ControlEmergency Access

EnvironmentalAesthetics

Ft McHenry Tunnel H3 Tetsuo Harano Tunnel

H3 Tetsuo Harano Tunnel



Chapter 3Geotech Investigations

IntroductionInformation StudySurveys and Site ReconnaissanceGeologic MappingSubsurface InvestigationsEnvironmental IssuesSeismicityAdditional Investigations During ConstructionGeospatial Data Management System

Geotechnical Investigations

As stated in Section 2.4.6 of AASHTO Manual on Subsurface Investigations (1988), “Design for underground construction is basically a geotechnical engineering effort, with project configuration being subject to the limitations imposed by soil and rock conditions and properties.”

Phased Geotech Investigations Phased Geotech InvestigationsConceptual Planning

Feasibility

Alternative /Route Study

Environmental Study/ Conceptual Design

Preliminary Design

Final Design

Construction

References

FHWA Geotechnical Engineering Circular No. 5 (FHWA, 2002a)FHWA Reference Manual for Subsurface Investigations – Geotechnical Site Characterization (FHWA, 2002b)FHWA Reference Manual for Rock Slopes (FHWA, 1999),andAASHTO Manual on Subsurface Investigations (AASHTO, 1988).

Tunnel Types

Planning/ Route Selection

Cut & Cover Tunnels

Mined/Bored Tunnels

Rock Tunneling

Water Land

Immersed Tunnels

Soft Ground Tunneling

Difficult Ground

Tunneling

SEM Tunneling



Components of Geotechnical Investigation Program

Information studySurveySite reconnaissanceGeologic mappingSubsurface explorationIn-situ and laboratory testingInstrumentation, and Other investigations made during and after construction

Geologic Mapping

Discontinuity typeDiscontinuity orientationDiscontinuity infillingDiscontinuity spacingDiscontinuity persistenceWeathering

Geologic Mapping

Slides, new or old, particularly in proposed portal and shaft areasMajor faultsRock weatheringSinkholes and karstic terrainGroundwater springsVolcanic activityAnhydrite, gypsum, pyrite, or swelling shalesStress relief cracksPresence of talus or bouldersThermal water (heat) and gas

Geological Setting

Manhattan Schist

Inwood Marble

Fordham Gneiss

Subsurface Investigations

Typically 3% to 5% of Construction CostPhased InvestigationsDefine subsurface profileEstimate geomaterial propertiesIdentify hydrogeological conditionsIdentify potential adverse geotechnical features (difficult ground issues)

Example Interpretive Profile



Subsurface Explorations and Field/Laboratory Testing

Borings to identify the subsurface stratigraphy and to obtain disturbed and undisturbed samples.In situ tests to obtain useful engineering and index properties. Geophysical tests to obtain subsurface information (stratigraphy and general engineering characteristics)Laboratory tests to provide a wide variety of engineering properties and index properties

Borehole Spacing

Horizontal Boring Groundwater Investigation

Observation of groundwater levels in boreholesAssessment of soil moisture changes in the boreholesGroundwater sampling for environmental testing Installation of groundwater observation wells and piezometersBorehole permeability tests (rising, falling and constant head tests; packer tests, etc.)Geophysical testing (see Section 3.5.4)Pumping tests

Seismic Considerations

Large ground displacements due to ground failure, i.e., fault rupture through a tunnelLandslide (especially at tunnel portals),Soil liquefactionChapter 13 – Seismic Considerations

Investigations During Construction

Borings/probings from the ground surfaceAdditional laboratory testing of soil and rock samplesGeologic mapping of the exposed tunnel faceGeotechnical instrumentationProbing/ Geophysical testing in advance of the tunnel heading from the face of the tunnelPilot TunnelsGroundwater observation wells and/or piezometersEnvironmental testing of soil and groundwater samples suspected to be contaminated or otherwise harmful



Mixed face condition High groundwater pressure Sensitive Clays Running Sands Faults and Shear Zones Squeezing and Swelling Ground Boulders and Obstacles Karstic Limestone Gassy ground High Temperature

Difficult Ground Conditions Data Management and Preservation

It often takes decades for a tunnel to be completedPreservation of rock and soil samples? Core scanningBorehole video and acoustic viewerGeospatial Data Management System

Chapter 4Geotechnical Reports

IntroductionGeotechnical Data ReportGeotechnical Design MemorandumGeotechnical Baseline Report

Geotechnical Reports

Originally based on 1997 Yellow Book –Geotechnical Baseline Reports for Underground ConstructionRevised based on Draft 2007 Geotechnical Baseline Reports for Construction – Suggested Guidelines

Geotechnical Reports

Geotechnical Data ReportGeotechnical Design MemorandumGeotechnical Baseline Report

Geotechnical Data Reports

Geotechnical factual data collected during investigation and design phases of the Project.Included as a contract documentDo not include any interpretation of data to avoid conflict with subsequent reports.



Geotechnical Design Memorandum

Geotechnical Interpretive ReportsFor internal use and considerations – NOT included in Contract DocumentNot to be used or confused with Baselines

Geotechnical Baseline Report

Geotechnical Design Summary ReportsGeotechnical Interpretive ReportsSet clear realistic baselines for conditions anticipated to be encountered during construction

TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 5


Chapter 5Cut and Cover TunnelsConstruction MethodologySupport of ExcavationStructural SystemsLoads and Load CombinationsStructural DesignGround Water ControlMaintenance and Protection of TrafficUtility Support/Relocation

Construction MethodologyBottom UpTop Down

Bottom Up Construction

Excavate OpeningInstall Support of ExcavationDeck Over ExcavationConstruct StructureBackfillRemove Support of ExcavationRestore Surface

Bottom Up Construction

Conventional TechniquesWaterproofing more easily AppliedDrainage Systems more easily InstalledExcavation Open and AccessibleRequires Larger FootprintRestoration of Surface can not Occur until Completion of Construction

Bottom Up Construction Bottom Up Construction



Top Down Construction

Excavate OpeningInstall Support of ExcavationInstall Bracing ElementsBracing Elements and Excavation Support Walls are the Final Structure


Deck over the ExcavationRemove Top Portions of Support of ExcavationBackfillRestore Surface


Allows Earlier Restoration of SurfaceSmaller FootprintEfficient Use of Structural ElementsTunnel Roof more Easily ConstructedWaterproofing more ComplicatedTight Installation Requirements RequiredAccess to Excavation Limited

Support of ExcavationOpen Cut

Sufficient Space for Cut SlopesSlope Stability

TemporaryInsufficient Space for Open CutSupports Vertical or Near Vertical FacesNot Part of the Tunnel StructureAbandoned In-Place or RemovedSoldier Piles and Lagging, Sheet Pile Walls, Slurry Walls, Secant Pile Walls, Tangent Pile WallsUnbraced, Braced, or Tied-Back

PermanentInsufficient Space for Open CutSupports Vertical or Near Vertical FacesForms Part of the Permanent StructureSlurry walls, Secant Pile walls, Tangent Pile wallsUnbraced, Braced, or Tied-Back

Support of ExcavationDesign Issues

Ground MovementDeflection of Support of Excavation Walls

Deflections are Not Recoverable and CumulativeDeflections must not Encroach on the Structural Envelop of the Permanent StructureWall StiffnessWall TypeSpacing of BracingTie-Backs

Consolidation Due to DewateringImpact on Adjacent Features

Support of ExcavationDesign Issues

Base StabilityCohesive Soils – HeaveGranular Soils - Quick

Water TightnessLocal draw Down of Water TableMovement of Hazardous Materials in GroundDry Working ConditionsFlooding of Excavation

Underpinning of Adjacent FacilitiesLocal draw Down of Water TableDefection of Support of Excavation Walls

Monitoring and InstrumentationMitigation Plans



Support of Excavation Support of Excavation

Tangent Pile Wall Tangent Pile Wall

Secant Pile Wall Secant Pile Wall



Structural SystemsStructural Element Sizing

Clear Space RequirementsVehicular Clearance – Horizontal & VerticalClearance to Appurtenances

Span LengthsStructural Depths

Vertical AlignmentDepth of ExcavationLength of Approaches

Structural SystemsFraming and Materials:

Temporary or Permanent Support of Excavation

Fixity of ConnectionsWaterproofing

Structural Steel encased in ConcreteSubject to Corrosion at Connections to Permanent Support of Excavation Walls

Cast-in-Place ConcretePrestressed Concrete

Cast-in-PlacePrecast

LoadsDead Loads

Structural MembersRoofCeilingWallsRoadway SlabFloor Slab

UtilitiesDrainageSignsSignalsCommunicationsVentilation

Loads (cont’d)Earth Loads

Horizontal – At RestVertical – AASHTO LRFD Provides GuidanceSurcharge – Minimum 400psf

Live LoadsOver TunnelInside Tunnel

BuoyancyExtreme Event

FireEarthquakeBlast

Loads (cont’d)Bottom Up Construction

Loads (cont’d)Top Down Construction



Load Combinations

At-rest earth pressure should be used for all conditions of design of cut and cover tunnel structures.Cut and cover tunnel structures are considered rigid frames.

Structural Design

Load Factors and CombinationsResistance Factors as per AASHTODuctility Factor = 1.0Redundancy Factor = 1.0Importance Factor = 1.05

Resistance FactorsReinforced Concrete (As Modified by Chapter 12 of AASHTO):

Flexure = 0.9Shear = 0.85Bearing = 0.7Compression = 0.75

Structural SteelFlexure = 1.0Shear = 1.0Compression (Steel Only) = 0.9Compression (Composite) = 0.9

Structural Analysis

Analyze Each Stage of ConstructionAnalysis Methods

Classical Frame AnalysisSoil Springs for Floor SlabSoil Structure Interaction3D Models for Complex Sections

Account for Secondary Effects

Groundwater ControlConstruction Dewatering

Impervious Retaining WallsWell Points (Drawdown)Ground Improvement (Chemical or Grout Injection)PumpingEffects of Lowering Groundwater must be ConsideredBase Stability

UpliftConnections to Excavation Support SystemThickening Structural Members to add Dead WeightWidening Floor Slab to Engage Soil WeightTension PilesPermanent Tie-Down AnchorsPermanent Pressure Relief System

Groundwater Discharge and Environmental Issues

Maintenance and Protection of Traffic



Utility Support and RelocationField Locate All UtilitiesExcavate to Expose UtilitiesIdentify Disposition

RelocateAbandonSupport in Place

Utility IssuesLong Lead Times (Energy Utilities)Functioning (i.e. Gravity Sewers)Hazardous MaterialsSensitivity to Ground MovementsAge and Condition

Utility Support and RelocationProcess

Identify Utilities and OwnersCoordinate with OwnersCoordinate Construction Schedule and StagingSurvey Existing ConditionEstablish Criteria for Allowable MovementEstablish Instrumentation RequirementsDevelop Procedures for Access During and After ConstructionDefine Easements and Prior Rights

3D Phasing & Cut-away Views

3D Phasing Example Questions?



Chapter 6Rock Tunneling

IntroductionRock Failure MechanismRock Mass ClassificationsRock Tunneling MethodsTypes of Rock Reinforcement and Excavation SupportDesign and Evaluation of Tunnel SupportsGroundwater Control During ExcavationPermanent Lining Design Issues

Introduction

Analysis, Design and ConstructionRange of Behavior

Coherent Continuum to DiscontinuumStabilization

No Support to Bolts to Sets to Reinforced Concrete

Vary Tunnel to Tunnel and Within A TunnelBe Prepared for Change

Rock Failure Mechanism

Rock Failure Mechanism

In Situ Stress Level and Rock Mass CharacteristicsShallow Depths, Blocky and Jointed

Gravity Falls of Wedges, BlocksGreat Depths

Failure of Rock MassSpalling, Slabbing, Rock Bursts

Wedge Failure

“Solid” Rock is a MisconceptionUsually Combination of Blocky Medium and ContinuumActs like DiscontinuumDepends on Character and Spacing of DiscontinuumHold Rock Together, Make it Form Ground Arch

Basic Information

DetermineRQDNumber of JointsJoint RoughnessJoint AlterationWater ConditionStress Condition



Basic Information

DetermineRQDNumber of JointsJoint RoughnessJoint AlterationWater ConditionStress Condition

Bases for Q SystemMore Later

The Challenge

Prevent Natural Tendency to UnravelInitiated by “Keyblocks” (Goodman 1980)Loosen and Come OutOthers FollowUntil it Stabilizes or Collapses

Step 1- Block A drops downStep 2- Block B rotates counterclockwise

and drops outStep 3- Block C rotates counterclockwise

and drops outStep 4- Block D drops out followed by block EStep 5- Block E drops out followed by block FStep 6- Block F rotates clockwise and drops out

Shotcrete

Rock Bolts

Step 1- Block A and C are held in place by rock bolts and shotcrete

Step 2- Block B is held in place by Blocks A and CStep 3- Block D is held in place by Blocks A, B,

and CStep 4- Blocks E and F are held in place by Blocks

A, B, and D assisted by rock bolts and shotcrete

Stabilizing Blocks

C

F

C

Squeezing and Swelling

SqueezingIn-Situ Uniaxial Compressive Strength << Excavation Induced Stress

SwellingIncrease in Moisture of RockCan be Related But Doesn’t Require SqueezingSupport Must Resist Full Swelling Pressure

It will form

Strain Squeezing Relationship

Rock Mass Classification Systems



Terzaghi’s Rock Mass (Tunnelman’s) Classification

Terzaghi’s Rock Mass (Tunnelman’s) Classification

RQD – Rock Quality Designation (Deere and Miller 1966)

Systematic Description of Rock Mass Quality From Rock CoresLength, as Percentage, of Intact and Sound Core Pieces Greater than Four Inches

Q System(Barton)

Traditional Six-Parameter (Q-Value) for Selecting Suitable Combinations of Shotcrete and/or Bolts For Rock Mass ReinforcementSix Parameters

RQD = Quality DesignationJn = Joint set NumberJr = Join Roughness NumberJu = Joint Alteration NumberJw = Joint Water FactorSRF = Stress Reduction Factor

⎥⎦⎤

⎢⎣⎡×⎥

⎦

⎤⎢⎣

⎡×⎥⎦

⎤⎢⎣

⎡=

SRFJ

JJ

JRQDQ w

a

r

n

Q System Equation

Q System

Three Major Components

= Measure of block size

= Measure of joint frictional strength

= Measure of Joint Stress

RQDJnJrJaJw

SRF

Based on more than 1000 tunnels



Q System Table 1

Q System Table 2

Q System Table 3

Q System Table 4

Q System Table 5

Q System Table 6



Rock Mass Rating (RMR)(Bienewski, 1989)

Uses Six ParametersUniaxial Compressive Strength (Intact)RQDDiscontinuity SpacingCondition of DiscontinuitiesGroundwater ConditionsOrientation of Discontinuities

Rock Mass Rating (RMR)


NumericalModeling

Rock Tunneling Methods

Drill and Blast

Controlled Blasting PrinciplesReliefDelay SequencingTunnel Blast SpecificsBurn CutPerimeter ControlArt vs. ScienceHire a Blast Consultant

Hemphill (1981)



Tunnel Boring Machines (TBM)

Tunnel Advance Rate (AR) Improvements Driven by Innovation

Alkirk TBM

Cutter Wheels with Carbide Inserts or Teeth

Disk Cutters



Disk Cutters

Disk Cutters

Modern Rock TBM

Machine Main and Support Elements

Complex Machine – Mechanisms for:

CuttingShovingSteeringGrippingShieldingExploratory Drilling

Ground Control and SupportLining ErectionMuck RemovalVentilationPower Supply

Machine Components

Machine Components Include Some or All:CutterGripper (Except Single Shield TBM)Shield (Except Open TBM)Thrust CylindersConveyorRock Reinforcement EquipmentComplete Trailing Gear

Fully Equipped Up To 1000 Ft or More

Open Main Beam

Single Shield

Double Shield



Put It All Together

Rock Bolt Drill Rig

Shotcrete Robot

Mesh Erector

Mesh Installed

Shielded TBM



1 Cutterhead2 Cutterhead Support3 Ring Erector4 Anchor Drilling Device5 Wire Mesh Erector

1

2

34

5

Multi Support TBM

Compatible Ground Support Elements

Roof BoltingSpiling/ForepolingPre-InjectionSteel Ring Beams with or without LaggingInvert SegmentShotcretePrecast Concrete Segment Lining

Machine Utilization

3.90%11.60%

5.60%

5%

4.90%

7.20%

10.40%

51.50%

Boring

Regrip

Cutters

TBM

Back-up

Water, vent, cable

Muck haulage

Others

Roadheaders

When Do Roadheaders Apply

Low Rock Strength – 20000 psi or even 15000Short RunsOne of a Kind OpeningOdd, Non-circular or Large ShapesConnection, Cross Passages, etcLow to Moderate AbrasivityPreferably Self-supporting RockNo or Small Inclusions-Chert etcNominal Water Pressure



Types of Rock Reinforcement and Excavation Support

Steel Rib Support

Lattice Girder

Spiling

Precast Concrete Segments

(a)

(b)



Design and Evaluation of Tunnel Supports

Tunnel Supports

TransitionFrom Support – Ribs/LaggingTo Reinforcement – Bolts, Dowels, Spiling, Lattice Girders, ShotcreteHold Rocks Together Prevent Block MovementGround Arch

Started on DC Subway

Empirical Methods

Empirical Methods

Cording, 1971

Empirical Methods

Cording, 1971

Empirical Methods

•Reinforcing Categories•Unsupported•Spot Bolting•Systematic Bolting•Systematic bolting with 40-100 mm unreinforced shotcrete•Fiber reinforced shotcrete, 50 - 90 mm, and bolting•Fiber reinforced shotcrete, 90 - 120 mm, and bolting•Fiber reinforced shotcrete, 120 - 150 mm, and bolting•Fiber reinforced shotcrete, > 150 mm with reinforced ribs of shotcrete and bolting•Cast concrete lining

(ESR=1)

Barton



Empirical Methods


Analytical Methods

Analytical Method

Kirsch Solution

σ =σff (1+ )a2

r2

Analytical Method(Hoek 1999)

Pcr = Critical Support Pressures -Prevents failure of rock mass around opening

Po = Hydrostatic Stressσ cm = Uniaxial Compressive Strength

(Rock Mass)ø = Angle of Fraction (Rock Mass)k = XXX

Pcr =2 Po - σ cm

1 + k

1 + SIN Ø

1 – SIN Ø

Analytical Method

Rock Arch – Bischoff and Smart



Analytical Methods Unwedge

3-D Stability Analysis (Computer) For Blocky Ground

Analytical Methods

Finite Element (FEM) or Finite Difference (FDM)Complex Computer Modeling OptionsWide Variety of Support Types

Analytical Methods

Typical Modeling Results - Coninuum

Analytical Methods

Typical Modeling Results – Discrete Element Method (DEM)Large Deformation and Finite Analysis of Blocky Ground

Analytical Methods Summary

Brady & Brown 1985

Groundwater Control

TerzaghiControl Takes Many FormsVaries Tunnel to Tunnel – Within a Tunnel



Groundwater Control Methods

UsualAt FaceProbe HolesPilot TunnelGroutingFreezingClosed Face Machine

OtherCompressed AirPanningDrain Fabric

Permanent Lining

Permanent Lining

Long Term SupportPrepare for End UseIncorporate Initial Support

Rock Loads

Section 6.6Roof, Side and EccentricEmpirical or Computer

Roof Load Side Load

Eccentric Load

40°

Permanent Lining Water Loads

Prefer to DrainMany Factors

Relative PermeabilityRelative StiffnessGeometric (e.g., Depth Below Water)

EmpiricalNumerical

Empirical Water Loads

Hydrostatic Pressure Line

10% or 25% of Hydrostatic Pressure at Invert Level



Water Loads Numerical Methods

100

200

300

400

500

600

Close view

Constant head boundary

Closure

Exciting EngineeringArt and ScienceOld and NewRapid ChangesDéjà Vu All Over Again



Chapter 7Soft Ground Tunneling Outline

Introduction Ground BehaviorExcavation MethodsGround Loads and Ground – Support Interaction Settlement Ground Stabilization Ground ImprovementImpact on and Protection of Surface Facilities

Introduction

1000’s of yearsDemand will GrowDiscuss Mostly Shield TunnelingSEM/NATM – Chapter 9Problematic Ground – Chapter 8Data Needed – Chapter 3GDM and GBR – Chapter 4

Tunnelmans Ground Classification

Ground with low frictional strength. Rate of squeeze depends on degree of overstress. Occurs at shallow to medium depth in clay of very soft to medium consistency.

Ground squeezes or extrudes plastically into tunnel, without visible fracturing or loss of continuity, and without perceptible increase in water content. Ductile, plastic yield and flow due to overstress.

Squeezing

Residual soils or sand with small amounts of binder may be fast raveling below the water tale, slow raveling above. Stiff fissured clays may be slow or fast raveling depending upon degree of overstress.

Chunks or flakes of material begin to drop out of the arch or walls sometime after the ground has been exposed, due to loosening or to over-stress and "brittle" fracture (ground separates or breaks along distinct surfaces, opposed to squeezing ground).

Slow raveling

-----Fast raveling

Raveling

Loess above water table; hard clay, marl, cemented sand and gravel when not highly overstressed.

Heading can be advanced without initial support, and final lining can be constructed before ground starts to move.

FirmTypical Soil TypesBehaviorClassification

Modified by Heuer (1974) from Terzaghi (1950)

Tunnelmans Ground Classification (cont’d)

Highly preconsolidated clay with plasticity index in excess of about 30

Ground absorbs water, increases in volume, and expands slowly into the tunnel.

Swelling

Below the water table in silt, sand, or gravel without enough clay content to give significant cohesion and plasticity. May also occur in highly sensitive clay when such material is disturbed.

A mixture of soil and water flows into the tunnel like a viscous fluid. The material can enter the tunnel from the invert as well as from the face, crown, and walls.

Flowing

Clean, dry granular materials. Apparent cohesion in moist sand, or weak cementation in any granular soil, may allow the material to stand for a brief period of raveling before it breaks down and runs. Such behavior is cohesive-running.

Granular materials without cohesion are unstable at a slope greater than their angle of repose (approx 30o -35o ). When exposed at steeper slopes they run like granulated sugar or dune sand until the slope flattens to the angle of repose.

Cohesive -running

-----Running

Running

Typical Soil TypesBehaviorClassification

Modified by Heuer (1974) from Terzaghi (1950)

Cohesive Soils and Silty Sand Above Water Table

Pz = Overburden PressurePa = Interior PressureSu = Undrained Shear Strength

Clayey Soils and Silty Sand



Sand and Gravels

Tunnel Behavior

Cohesionless Soils Below Water TablesCan run or flow, cleaner more so

Maintain Stability

Equilibrium Changing Stresses – Starts ahead of face Accompanied by Distortions

In medium and supportsSome is beneficial – too much detrimental

Brunel’s Discovery

Maintain Stability Limit size Match size to ground behavior, supportMany factors involved

Brunel Shield

Brunel Shield – Thames River



JEM Design - Mexico

1960’s – 1970’s

1960’s – 1970’s

Earth Pressure Balance Machine (EPB)

soil + water pressure

Earth Pressure Balance Machine

Earth Pressure Balance TBM



Earth Pressure Balance TBM

EPB Shield, Belt Conveyor Outlet

Slurry Face Machine

Slurry Face Machine

Slurry Face Machine

Slurry Separation Plant



Choosing Between EPB And SFM

EPBSilty Ground High Percent FinesPermeability less than 10 – 5 m/sHigher permeability requires increased percentage of conditioners

Choosing Between EPB and SFM

SFMPermeability Fines > 20% may rule it out High Plasticity clays – balling – and problems at treatment plant

Conditioning Agents

Ground Loads and Ground –Support Interaction

Tunnel Support SystemStabilize tunneling headingMinimize ground movementProvide design life

Two types of loading Overpressure LoadingExcavation Loading


Overpressure LoadingGround Isolated – UnstressedExcavate Tunnel, Install LiningApply Soil (Freefield) Stresses to Boundary

See Chapter 10


Excavation LoadingGround Isolated – UnstressedApply Insitu StressesConstruct Tunnel in Stressed Groundmass

See Chapter 10

Analytical Solutions

Ground – Support InteractionSolutions Include

1. Morgan – 19612. Burns and Richard – 19643. Hoeg – 19684. Peck. Hendron Mohraz – 19725. Dar and Bates – 19746. Muir – Wood – 19757. Curtis – 19768. Rankin, Ghabouss, and Hendrois – 19789. Einstein ET Al - 198010. Wu and Penzien – 1997

See Appendix



Simplified Loads for Initial Tunnel Support

Table 7-6 Initial Support Loads for Tunnels in Soft Ground

Numerical Methods

Loads on a Concrete Lining Calculated by Finite Element Analysis

(a) Axial Force

(b) Bending

(c) Shear

Tunneling Induced Settlement

More for soft GroundTypically more facilities

Sources of lost Ground

Face – movement in front of and into shield Running, flowing, caving, squeezing

Shield – Between cutting edge and tailYawing, pitching, plowing, cornering

Tail Vacated by tail To erect segments Prevent iron bindingTends to fill rapidly

Settlement Calculations

Modified from Terzaghi

Approx. Settlement Curve

Figure 7-9 Typical Settlement Profile for a Soft Ground Tunneling



Ground Stabilization/ Improvement

Stabilize ground for excavation Contribute to its own stability

Final lining is less costly

Soil nailsMicro piles Grouting

Permeation Compaction CompensationJet grouting

Ground freezing

Ground Stabilization/ Improvement

Impact on and Protection of Surface Facilities

Tolerance to SettlementArchitectural Damage – Appearance, not functionFunctional – Requires non-structural repairStructural – Affecting Stability

Impact, Continued

Table 7-8 Limiting Angular Distortion (Wahls, 1981) a Safe limit includes a factor of safety.

Impact, Continued

Rankin, 1988

Structure Protection (Mitigating Settlement)

Proper Construction Means, MethodsRequire Closed Face MachineGrout Annular SpaleControl Operation (Steering) –

One Percent Correction = 1.5% Ground LossCompaction or Consolidation GroutTreat (Stabilize) Loose Soil Before TunnelingUnderpinFreeze



Soft Ground Tunneling Closure

Great Strides ForwardClose Face MachinesGround TreatmentHold Settlement to Less than 3/8 in.

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