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1Geotechnical Investigation for the
Second Avenue Subway in New York
Verya Nasri, PhD, PE
Planning and Development of Underground Space,
HKIE and HKIP
PROJECT PHASING PLAN
Phase 2125th to 96thPhase 3
63rd to Houston
Phase 196th to 63rd
Phase 4
Houston to Hanover
272nd ST. and 86th ST. STATIONS
72nd ST. STATION
372nd ST. STATION
72nd ST. STATION
4PUBLIC CAVERN
ANCILLARY CAVERN
5FOLIATED METAMORPHIC ROCK
180 new borings in Phase 1 Area
Cavern crown centerline borings (rock cover)
Two inclined borings in cavern at 72nd St
Historic borings
Environmental borings
GEOTECHNICAL BORINGS
6SUBSURFACE TESTING AND
EXPLORATION PROGRAM
Orientation and frequency of fracturesShear strength properties of fractures
Abrasivity of rock
Faults and shear zones
Intrusions and alteration
Rock material properties
Rock mass properties
Soil-rock interface profile and condition
GENERAL TESTS
Uniaxial Compression
Point Load Strength
Deformation Properties
Brazilian Tensile Strength
Direct Shear of Joints
MACHINE TESTS
Cerchar Abrasivity
Petrographic Analyses
Drill Rate Index
Bit Wear Index
Cutter Life Index
LABORATORY TESTING - ROCK
7The quality of the
rock can change
in very small
distances
VARIABILITY IN ROCK QUALITY
ATV image
Core
CORRELATION OF CORE AND
ACOUSTIC IMAGE
8GEOLOGIC INTERPRETATION
Interpreted conjugate faults
JOINT WAVINESS
Manhattan Schist
9ROCK WEDGE
Deep wedge
stable with irregular joints
Deep wedge
can be unstable if friction angle &
dilatancy is low, occurs with:
continuous, sheared, planar joints.
EMPIRICAL DESIGN (Q)
Span
Span
Span
Crown
Zone used for determining representative
Q values, obtained using the weighted
average of the raw Q values for each core
run within the zone.
Rock
Surface
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CONTINUUM ANALYSIS
2D modeling Hoek-Brown Failure Criterion 50 % Relaxation, Shotcrete Strength Varied With Excavation Sequence
ROCK MASS PARAMETERS
Input- Intact Uniaxial Compressive Strength (UCS)- Intact Rock Modulus (Ei)- Disturbance Factor (D)- Geological Strength Index (GSI)- Intact Rock Parameter (mi)
Output- Hoek-Brown Strength Parameters- Rockmass Deformation Modulus
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EXCAVATION SEQUENCE
CONTINUUM ANALYSIS RESULTS
No Yielding of Initial Support Small Ground Surface Deformations (5 to 10 mm)
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TYPES OF DISCONTINUITIES
FOLIATION
SUBVERTICAL STRUCTUREFAULT / SHEAR ZONE
CONJUGATE JOINTS
CLUSTER
CONSTITUTIVE MODELS
Rock constitutive model: Mohr-Coulomb elastic/plastic failure
Joint constitutive model: Barton-Bandis joint model
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No Axial Failure
Local Axial Failure
Bolt Axial Load
Bolt Axial Load
BOLT AXIAL LOADS AND FAILURE
Maximum Settlement3.4 mm
EXPECTED CASE SETTLEMENT
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Maximum Settlement14 mm
WORST CASE SETTLEMENT
Expected Case
Maximum Settlement3.4 mm
Maximum Settlement14 mm
Worst Case
SETTLEMENT AT TOP OF ROCK
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TRIDIMENSIONAL CONTINUUM (FLAC3D)
MODELING
TRIDIMENSIONAL CONTINUUM (FLAC3D)
MODELING
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TRIDIMENSIONAL CONTINUUM (MIDAS)
MODELING
TRIDIMENSIONAL DISCONTINUUM
(3DEC) MODELING
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TRIDIMENSIONAL DISCONTINUUM
(3DEC) MODELING
Stress Distribution in Shotcrete Liner
EXCAVATION SEQUENCE
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STATION CAVERN
Excavation Sequence and Support
STATION CAVERN
Excavation Sequence and Support
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STATION CAVERN
Excavation Sequence and Support
No need for final lining
Drained, no water pressure (%25 assumed)
Rock load, capacity of bolts
Rock-liner interface
FINAL LINER DESIGN
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Design for Environment
Architecture: 96th St. Entrance 3
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Architecture: 86th St. Entrance 2
Architecture: 72nd St. Entrance 3
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Architecture: 86th St. Ancillary 1
Secant Pile Walls
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Secant Pile Walls, Toe Anchors
Slurry Walls, Permanent Station Walls
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Rebar Cage Lift
100 Right of Way
41 Travel Way 42 Work Zone
10 ft
96th St. Station, Street Cross Section
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94th to 95th Streets, Temporary Decking
Launch Box Excavation
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Starter Tunnels
TBM
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TBM Tunnel
72nd Street Shaft
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72nd Street Shaft
Drill and Blast Design
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Overbreak and Profile Control
Vibration and Damage Control
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Vibration Control
Center Drift of Top Heading
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Side Drift of Top Heading
Penetration
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TBM Tunnel Enlargement
East Side Access Station Caverns in New York
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East Side Access Station Caverns in New York
East Side Access Station Caverns in New York
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Updated 0508
Trans Hudson Express Station Cavern
Trans Hudson Express Station Cavern
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High Speed Train Station in New York (Concept)
Indianapolis Pump Station Cavern
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Designed by Santiago Calatrava
World Trade Center, New York
The Future