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