Planning and Development of Underground Space,
HKIE and HKIP
Geotechnical Investigation for the
Second Avenue Subway in New York
Verya Nasri, PhD, PE
PROJECT PHASING PLAN
Phase 3
63rd to Houston
Phase 1
Phase 2
125th to 96th
96th to 63rd
Phase 4
Houston to Hanover
1
72nd ST. and 86th ST. STATIONS
72nd ST. STATION
2
72nd ST. STATION
72nd ST. STATION
3
PUBLIC CAVERN
ANCILLARY CAVERN
4
FOLIATED METAMORPHIC ROCK
GEOTECHNICAL BORINGS

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
5
SUBSURFACE TESTING AND
EXPLORATION PROGRAM
•Orientation and frequency of fractures
•Shear 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
LABORATORY TESTING - ROCK
GENERAL TESTS
MACHINE TESTS
• Uniaxial Compression
• Cerchar Abrasivity
• Point Load Strength
• Petrographic Analyses
• Deformation Properties
• Drill Rate Index
• Brazilian Tensile Strength
• Bit Wear Index
• Direct Shear of Joints
• Cutter Life Index
6
VARIABILITY IN ROCK QUALITY
The quality of the
rock can change
in very small
distances
CORRELATION OF CORE AND
ACOUSTIC IMAGE
Core
ATV image
7
GEOLOGIC INTERPRETATION
Interpreted conjugate faults
JOINT “WAVINESS”
Manhattan Schist
8
ROCK WEDGE
Deep wedge
Deep wedge
can be unstable if friction angle &
dilatancy is low, occurs with:
continuous, sheared, planar joints.
stable with irregular joints
EMPIRICAL DESIGN (Q)
Rock
Surface
Zone used for determining representative
Q values, obtained using the weighted
average of the raw Q values for each core
run within the zone.
Crown
¼
Span
¼
Span
Span
9
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
10
EXCAVATION SEQUENCE
CONTINUUM ANALYSIS RESULTS
• No Yielding of Initial Support
• Small Ground Surface Deformations (5 to 10 mm)
11
TYPES OF DISCONTINUITIES
CONJUGATE JOINTS
FOLIATION
CLUSTER
SUBVERTICAL STRUCTURE
FAULT / SHEAR ZONE
CONSTITUTIVE MODELS
Rock constitutive model: Mohr-Coulomb elastic/plastic failure
Joint constitutive model: Barton-Bandis joint model
12
BOLT AXIAL LOADS AND FAILURE
Bolt Axial Load
No Axial Failure
Bolt Axial Load
Local Axial Failure
EXPECTED CASE SETTLEMENT
Maximum Settlement
3.4 mm
13
WORST CASE SETTLEMENT
Maximum Settlement
14 mm
SETTLEMENT AT TOP OF ROCK
Expected Case
Worst Case
Maximum Settlement
3.4 mm
Maximum Settlement
14 mm
14
TRIDIMENSIONAL CONTINUUM (FLAC3D)
MODELING
TRIDIMENSIONAL CONTINUUM (FLAC3D)
MODELING
15
TRIDIMENSIONAL CONTINUUM (MIDAS)
MODELING
TRIDIMENSIONAL DISCONTINUUM
(3DEC) MODELING
16
TRIDIMENSIONAL DISCONTINUUM
(3DEC) MODELING
Stress Distribution in Shotcrete Liner
EXCAVATION SEQUENCE
17
STATION CAVERN
Excavation Sequence and Support
STATION CAVERN
Excavation Sequence and Support
18
STATION CAVERN
Excavation Sequence and Support
FINAL LINER DESIGN
 No need for final lining
 Drained, no water pressure (%25 assumed)
 Rock load, capacity of bolts
 Rock-liner interface
19
Design for Environment
Architecture: 96th St. Entrance 3
20
Architecture: 86th St. Entrance 2
Architecture: 72nd St. Entrance 3
21
Architecture: 86th St. Ancillary 1
Secant Pile Walls
22
Secant Pile Walls, Toe Anchors
Slurry Walls, Permanent Station Walls
23
Rebar Cage Lift
96th St. Station, Street Cross Section
100’ Right of Way
41’ Travel Way
42’ Work Zone
10 ft
24
94th to 95th Streets, Temporary Decking
Launch Box Excavation
25
Starter Tunnels
TBM
26
TBM Tunnel
72nd Street Shaft
27
72nd Street Shaft
Drill and Blast Design
28
Overbreak and Profile Control
Vibration and Damage Control
29
Vibration Control
Center Drift of Top Heading
30
Side Drift of Top Heading
Penetration
31
TBM Tunnel Enlargement
East Side Access Station Caverns in New York
32
East Side Access Station Caverns in New York
East Side Access Station Caverns in New York
33
Trans Hudson Express Station Cavern
Updated 0508
Trans Hudson Express Station Cavern
34
High Speed Train Station in New York (Concept)
Indianapolis Pump Station Cavern
35
World Trade Center, New York
Designed by Santiago Calatrava
The Future
36