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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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 1&2
Parsons Brinckerhoff 2
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 1&2
Parsons Brinckerhoff 3
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 1&2
Parsons Brinckerhoff 4
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 1&2
Parsons Brinckerhoff 5
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 1&2
Parsons Brinckerhoff 6
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 1&2
Parsons Brinckerhoff 7
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 1&2
Parsons Brinckerhoff 8
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 1&2
Parsons Brinckerhoff 9
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 3&4
Parsons Brinckerhoff 1
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 3&4
Parsons Brinckerhoff 2
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 3&4
Parsons Brinckerhoff 3
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 3&4
Parsons Brinckerhoff 4
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.
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 3&4
Parsons Brinckerhoff 5
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
Parsons Brinckerhoff 1
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 5
Parsons Brinckerhoff 2
Bottom Up Construction Bottom Up Construction
Bottom Up Construction Bottom Up Construction
Bottom Up Construction Bottom Up Construction
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 5
Parsons Brinckerhoff 3
Top Down Construction
Excavate OpeningInstall Support of ExcavationInstall Bracing ElementsBracing Elements and Excavation Support Walls are the Final Structure
Top Down Construction
Deck over the ExcavationRemove Top Portions of Support of ExcavationBackfillRestore Surface
Top Down Construction
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 5
Parsons Brinckerhoff 4
Support of Excavation Support of Excavation
Tangent Pile Wall Tangent Pile Wall
Secant Pile Wall Secant Pile Wall
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 5
Parsons Brinckerhoff 5
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 5
Parsons Brinckerhoff 6
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 5
Parsons Brinckerhoff 7
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?
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 6
Parsons Brinckerhoff 1
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 6
Parsons Brinckerhoff 2
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 6
Parsons Brinckerhoff 3
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 6
Parsons Brinckerhoff 4
Q System Table 1
Q System Table 2
Q System Table 3
Q System Table 4
Q System Table 5
Q System Table 6
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Parsons Brinckerhoff 5
Rock Mass Rating (RMR)(Bienewski, 1989)
Uses Six ParametersUniaxial Compressive Strength (Intact)RQDDiscontinuity SpacingCondition of DiscontinuitiesGroundwater ConditionsOrientation of Discontinuities
Rock Mass Rating (RMR)
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)
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Parsons Brinckerhoff 6
Tunnel Boring Machines (TBM)
Tunnel Advance Rate (AR) Improvements Driven by Innovation
Alkirk TBM
Cutter Wheels with Carbide Inserts or Teeth
Disk Cutters
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 6
Parsons Brinckerhoff 7
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
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Parsons Brinckerhoff 8
Put It All Together
Rock Bolt Drill Rig
Shotcrete Robot
Mesh Erector
Mesh Installed
Shielded TBM
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Parsons Brinckerhoff 9
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 6
Parsons Brinckerhoff 10
Types of Rock Reinforcement and Excavation Support
Steel Rib Support
Lattice Girder
Spiling
Precast Concrete Segments
(a)
(b)
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 6
Parsons Brinckerhoff 11
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
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Parsons Brinckerhoff 12
Empirical Methods
Rock Mass Rating (RMR)
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
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Parsons Brinckerhoff 13
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
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Parsons Brinckerhoff 14
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 6
Parsons Brinckerhoff 15
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 7
Parsons Brinckerhoff 1
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 7
Parsons Brinckerhoff 2
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 7
Parsons Brinckerhoff 3
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 7
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Earth Pressure Balance TBM
EPB Shield, Belt Conveyor Outlet
Slurry Face Machine
Slurry Face Machine
Slurry Face Machine
Slurry Separation Plant
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 7
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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
Ground Loads and Ground –Support Interaction
Overpressure LoadingGround Isolated – UnstressedExcavate Tunnel, Install LiningApply Soil (Freefield) Stresses to Boundary
See Chapter 10
Ground Loads and Ground –Support Interaction
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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 7
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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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 7
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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
TRB Workshop - 1/11/09 FHWA Road Tunnel Manual Ch 7
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Soft Ground Tunneling Closure
Great Strides ForwardClose Face MachinesGround TreatmentHold Settlement to Less than 3/8 in.