Geotechnical Risk for Underground Construction · 3. Abrasivity 4. TBM Performance 5. Friction 6....
Transcript of Geotechnical Risk for Underground Construction · 3. Abrasivity 4. TBM Performance 5. Friction 6....
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Agenda1. Obstructions2. Mixed Ground / Mixed Face 3. Abrasivity4. TBM Performance 5. Friction6. Thrust Restraint7. Stickiness8. Sensitive Soils9. Fines in Slurry10. Slaking, Raveling, & Invert
Degradation
11. Groundwater Control12. Faults 13. Heavy Ground14. Squeezing Ground 15. Rock Burst16. Hydrothermal Conditions17. Hazardous Gas18. Settlement19. Flowing Ground
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Obstructions:Risk
Abandoned Ground Support Systems
Steel Pipe Obstruction
BouldersWells and Casings
Piles and Building FoundationsOld Foundation Block
Photo Credit:TunnelTalk
Photo Credit: Stantec
Photo Credit: Stantec Photo Credit: The Seattle Times
Photo Credit: Stantec Photo Credit: Stantec
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Obstructions: Characterization
The picture can't be displayed.
Photo Credit: Stantec
Photo Credit: Stantec
Photo Credit: Stantec
Photo Credit: Stantec Photo Credit: Stantec
Photo Credit: Stantec
Photo Credit: Tunnel Geophysics Image Search
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Obstructions:Mitigation
Photo Credit: Akkerman
Photo Credit: AkkermanPhoto Credit: Stantec
Photo Credit: Herrenknecht
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Mixed Ground:Risk
VS
Photo Credit: Soumagne Tunnel
Photo Credit: Stantec
Photo Credit: GeoHazards
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Mixed Face:Risk
STATION
ELEVATION
MTBM PIPELINE CROSSINGAT .25% SLOPE
Photo Credit: Portland Water Bureau
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Mixed Face: Characterization
Photo Credit: Stantec
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Mixed Face: Mitigation
Photo Credit: Hayward Baaker
Photo Credit: StantecPhoto Credit: Daegu Metropolitan
Photo Credit: Stantec
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Abrasivity: Risk
Photo Credit: Stantec
Photo Credit: Stantec
Photo Credit: Stantec
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Abrasivity: Characterization
Granitic Porphyry Thin SectionPhoto Credit: Colorado School of Mines
Photo Credit: St. Cloud Granite
Photo Credit: Colorado School of Mines
Photo Credit: Colorado School of Mines
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Millers Drilling Index (ASTM G75-01)
RAR:Relative Abrasion Resistance
Abrasivity: Characterization
Photo Credit: Norwegian University of Science and Technology
Photo Credit: ASTM
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Abrasivity: Mitigation
TBM/Disc Cutter Mechanic Shop
Photo Credit: Alimineti Madhava Reddy Tunnel ProjectPhoto Credit: Trakkom
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Abrasivity: Mitigation
Photo Credit: MecTunnelPhoto Credit: PressureWorx
Photo Credit: Levent OzdemirPhoto Credit: Herrenknecht
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TBM Performance:
Risk
Photo Credit: Stantec
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Unconfined Compressive Strength
TBM Performance:
CharacterizationBrazilian Tensile Strength
Resiliency (Toughness)
Photo Credit: Colorado School of MinesPhoto Credit: Colorado Scool of MinesPhoto Credit: Colorado School of Mines
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TBM Performance:
Mitigation
Photo Credit: Colorado School of Mines
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General Description Grain Shape Loose, φ (deg) Dense, φ (deg)
Ottawa Standard Sand Well Rounded 28 35
Sand from St. Peter sandstone Rounded 31 37
Silty sand from Franklin Falls Dam site, NH
Subrounded 33 37
Silty sand from vicinity of John Martin Dam, CO
Subangular to Subrounded
36 40
Sand from Great Salt Lake Angular 38 47
Well-graded, compacted crushed rock
Angular - 60
Friction:Risk
Photo Credit: Holtz & Kovacs, 1981
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Friction: Characterization
Photo Credit: Stantec
Photo Credit: Retsch
Photo Credit: Stantec
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Interjack Installation
Intermediate Jacking
Pin Lube System
Friction:Mitigation
Photo Credit: Herrenknecht
Photo Credit: Herrenknecht
Photo Credit: Stantec
Photo Credit: Stantec
Automated Pipe Lubrication
Photo Credit: Tunneling and Underground Space Technology
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Concrete Thrust Block
Thrust Restraint
Photo Credit: Stantec
Photo Credit: Stantec
Photo Credit: Stantec
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𝑃𝑃𝑢𝑢𝑢𝑢𝑢𝑢 = ℎ +𝐻𝐻2 𝛾𝛾 tan2 45 +
𝜑𝜑2 + 2𝑐𝑐 tan2 45 +
𝜑𝜑2 𝐻𝐻𝐻𝐻
Pult = Passive resistance of thrust blockγ = Soil unit weightH = Height of thrust blockh = Depth to top of thrust blockB = Width of thrust blockφ = Soil friction anglec = Soil cohesion
𝛿𝛿 =𝑞𝑞𝐻𝐻 1 − 𝑢𝑢2
𝐸𝐸𝑠𝑠
THRUST BLOCK DEFORMATIONFor a square thrust block of B, it is
q = Bearing pressure on thrust blockυ = Poisson’s RatioEs = Young’s Modulus of the soil
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Thrust Restraint: Mitigation
Photo Credit: Stantec
Photo Credit: Collucio Construction
Photo Credit: Collucio Construction
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Stickiness: Risk
Photo Credit: Stantec
Photo Credit: Stantec
Photo Credit: Stantec
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Stickiness: Characterization
Photo Credit: Stantec
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Different Conditioners• Dispersants• Polymer • Limited amounts of water• Jetting or hand removal
Stickiness: Mitigation
Photo Credit: Stantec
Photo Credit: Herrenknecht
Photo Credit: Jaybee Fluids
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Sensitive Soils: Risk
GRANBY STREET SEWERHartford, CT
• Encountered very sensitive varved clays.
• Three tunnels constructed via microtunneling for 2,500 linear feet total.
Photo Credit: Stantec
Photo Credit: Stantec
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Ratio of Unconfined Compressive Strength of an undisturbed soil specimen to its unconfined strength after remolding
Sensitive Soils: Characterization
Photo Credit: Soil Mechanics – Soil Classification and Compaction
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Sensitive Soils: Mitigation
Photo Credit: Mitchell, 1981
Photo Credit: Stantec
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Fines in Slurry: Risk
Photo Credit: Slurry Separation Image Search
Photo Credit: Stantec
Photo Credit: Stantec
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Hydrometer Test
Fines in Slurry: Characterization
Photo Credit: International Journal of Geosciences
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Fines in Slurry: Mitigation
Photo Credit: GN Solids Control
Photo Credit: GN Solids ControlPhoto Credit: GN Solids Control
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Slaking, Raveling, & Invert Degradation:
Risk
Photo Credit: Underground Raveling Image Search
Photo Credit: StantecPhoto Credit: Seismic Performance of Rock Block Structures
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Slaking, Raveling, & Invert Degradation:
Characterization
Photo Credit: Colorado School of Mines
Photo Credit: Colorado School of Mines
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Slaking, Raveling, & Invert Degradation:
Mitigation
Photo Credit: Potenza Photo Credit: Tekflex – Minova
Photo Credit: East End Bridge Tunnel
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Groundwater Control:
Risk
Photo Credit: Stantec
Photo Credit: Stantec
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Groundwater Control:
Characterization
Photo Credit: Stantec
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Groundwater Control:
Characterization
Multi-level Single
Typical stand-pipe piezometer Multi-level vibrating wire piezometer
Fully Grouted Multi-level vibrating wire piezometer
Photo Credit: Stantec Photo Credit: StantecPhoto Credit: Geokon
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Groundwater Control:
Characterization • Packer Testing (Single & Double)• Constant Head• Falling Head• Pump Test
Tunnel Alignment
Photo Credit: Stantec
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Groundwater Control:
Mitigation
Photo Credit: Newman Dewatering
Photo Credit: Herrenknecht
Photo Credit: Robbins
Photo Credit: TunnelTalk
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Faults: Risk
2+44
Fault “A”
Fault “B”
Fault “B” right side Chamber
High Angle Normal Fault
Photo Credit: Stantec
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Faults: Characterization
Fault exposed in tunnel & discontinuitydata collected to document it
Aerial Photo Lineation MapFault/Lineation MapPhoto Credit: Stantec
Photo Credit:
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Probe Drill/Grout
Faults: Mitigation
Grouting Array
High Groundwater Inflows
Photo Credit: TunnelTalk
Photo Credit: TunnelTalk Photo Credit: Trevor Carter
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• Unable to advance TBM due to immense pressures
• Encountered in deep, fault zones
Heavy Ground: Risk
Photo Credit: McMillen Jacobs Associates
Photo Credit: Stantec
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Heavy Ground: Characterization
• Drill hole through faults from surface • RQD values• Probe drilling in tunnel
RQD %= 50%= 50%= 14%= 92%= 43%= 100%
Photo Credit: Stantec
Photo Credit: Pula Subbaiah Veligonda Tunnel
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• Heavy support• Pre-support• Spiling• Thicker shield• Don’t stop progress
Heavy Ground: Mitigation
Photo Credit: J.F. Shea – 2012 NAT
Photo Credit: J F Shea – 2012 NAT Photo Credit: J F Shea – 2012 NAT
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Heavy Ground: Mitigation
Photo Credit: McMillen Jacobs Associates
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Squeezing Ground:
Risk
Photo Credit: Squeezing Soil Image SearchPhoto Credit: Stantec
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• Rule of thumb—UCS vs overburden stress
• Strength/stress ratio• Modeling • Linear into plastic
Squeezing Ground:
Characterization
Photo Credit: Trevor Carter
Photo Credit: Stantec
Photo Credit: Tunneling in Squeezing Ground
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Squeezing Ground:
Mitigation
Hand mining over the TBM shield
• Yielding support • Ribs w/ slides • American commercial • TBM shield is tapered • Shotcrete—jacks between
shotcrete panels
Photo Credit: StantecPhoto Credit: DSI Underground / Jennmar
Photo Credit: Giovanni & Marco Barla
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• In-situ Stress• Brittleness• Stored Energy• Released Energy
Rock Burst:Risk
Photo Credit: Stantec
Photo Credit: Stantec
Photo Credit: Stantec
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2nd Video Rock Burst:
Risk
Video Credit: McNally Support System - Robbins
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Rock Burst:Characterization
Photo Credit: Goodman Jack - DGSI
Photo Credit: Stantec
Photo Credit: StantecPhoto Credit: Hydrofrac
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Rock Burst: Mitigation
Drilling of horizontal and vertical relief holes, and shotcrete application
Photo Credit: Journal of the Southern African Institute of Mining and Metallurgy
Photo Credit: StantecPhoto Credit: Mirarco
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Hydrothermal Conditions:
Risk
Photo Credit: Tunneltalk
Geothermal Inflow, Iceland
Photo Credit: Stantec
Photo Credit: Stantec
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• Pictures from Simon?
Hydrothermal Conditions:
Characterization
Geothermal Gradient Map, CO
Upper Colorado River Hot Spring
Temperature Gradient w/ Depth
Mapped Hot Springs
Photo Credit: Stantec
Photo Credit: Stantec
Photo Credit: Stantec
Photo Credit: Stantec
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Hydrothermal Conditions:Mitigation
Increased ventilation
Ice VestMandatory Breaks & Limited Working Hours Photo Credit: Utrop
Photo Credit: SRK Consulting
Photo Credit: Glaciertek
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Hazardous Gas: Risk
Photo Credit: TunnelTalk
Photo Credit: Ashley Pon/Getty Images
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Petroleum fields: CH4
Hazardous Gas: Characterization
Bacteria Geothermal fields: CO2
Aerobes: CO2Sulfate reducers: H2SMethanogens: CH4
Photo Credit: MicrobeWiki – Kenyon College Photo Credit: Geothermal Education Office
Photo Credit: KQED Science Photo Credit: flickr
Gas station: gasoline vapors
Hydrothermal Alteration: H2SPhoto Credit: James Maynard
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Hazardous Gas:Characterization
Groundwater samplingPore gas sampling
Sample ScreeningPhoto Credit: Stantec
Photo Credit: Stantec Photo Credit: Stantec
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Hazardous Gas: Mitigation
Mechanical Controls
System Monitoring
Crew TrainingPhoto Credit: Stantec Photo Credit: Stantec
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Settlement: Risk
King Street in Seattle, above Bertha TBM Photo Credit: KIRO 7 News
Photo Credit: Stantec
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Settlement: Characterization
Photo Credit: Stantec
Photo Credit: Stantec
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Settlement:Mitigation
Photo Credit: Bft International
Photo Credit: Dogus
Photo Credit: Dragageshk
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Settlement should be controlled by:• Designing construction methods to
prevent settlement• Continued monitoring of surface
and subsurface conditions for settlement or indicators
• Extensometers
Settlement: Mitigation
Photo Credit: Bor-ExPhoto Credit: Geokon
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Settlement:Mitigation
Photo Credit: Stantec
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wet sand
Sinkhole
Flowing, running ground
wet fine sand
clay
silt
Flowing Ground in TBM
Flowing Ground: Risk
Photo Credit: Stantec
Photo Credit: Stantec
Photo Credit: Stantec
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Different Conditioners• Dispersants• Foam Injection Ratios• High Density Limestone Slurry• Bentonite • Polymer
Flowing Ground: Mitigation
Photo Credit: Tunnelling and Supported Deep Excavations in the Greater Cairo
Photo Credit: Hatch Mott MacDonald
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Surprises Are Inevitable —There will always be unexpected ground conditions and neither the owner nor the design team can completely eliminate surprises from complex underground projects.
Gould, 1995
Photo Credit: Stantec
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Thank you