Second Avenue Subway, New York Geotechnical Design and Construction
Chu Ho Sc.D., P.Eng., M.ASCE Arup, New York TEAM
• Owner & Program Manager • Design Consultant • Consultant Construction Manager 8. 5 miles of new subway 16 new stations 1 renovated station Yards for 28 trains
2 services, TT& Q Connection to existing Q line Transfers to 7 other rail lines Phase 2
Phase 1
Phase 4
(Existing) Lexington Ave/ 63rd Street Station
Phase 3 Phase 1 – Construction In Progress
96th Street Station (Cut & Cover)
63rd Street/ 86th Street Station Lexington Ave Station (Rock Cavern) (Existing)
72nd Street Station (Rock Cavern) Phase 1 – Subway Alignment Geology
Existing Tunnel
(Existing) Lexington 72nd St 86th St 96th St Ave / Station Station Station 63rd St Station
Subsurface Stratification Fill Organics Silty Sand Varved Silt/Clay Glacial Till Decomposed Rock Bedrock (Manhattan Schist) Rock Caverns and Tunnels Rock Tunnels
Ground Level
45’-85’
Top of Rock
15’-70’
6m (19’-99)”)ID ID 6. 75m (22’-1”) OD Steel Fiber Reinforced Concrete Lining TBM Tunneling • Hard rock TBM drives • Abrasive rock • Faults and shear zones • Curve towards 63rd Street (616’ Min Radius) • Water-bearing fissures • Final lining omitted through future cavern zones Soft Ground Conditions 92nd Street 93rd Street 94th Street
Top of rock
96th Street Station (Cut and Cover)
96th St Station
(Existing) Lexington Ave / 72nd St Station 86th St Station 63rd St Station
Subsurface Stratification Fill Organics Silty Sand Varved Silt/Clay Glacial Till Decomposed Rock Bedrock (Manhattan Schist) 96th Street Station (Cut and Cover)
TBM Launch Shaft 92nd Street 93rd Street Entrance 2 (Temporary secant pile wall) (Slurry wall)
Permanent station slurry wall Entrance 2 Ancillary 1 (Slurry wall) (Permanent secant pile wall)
Entrance 3 Ancillary 2 (Slurry wall) (Permanent secant pile wall) Existing Tunnel
Link to Existing Tunnel (Temporary Secant pile wall) TEMPORARY SECANT PILE WALLS AT TBM LAUNCH BOX
West Typical East Design Profile
Fill
Sand
Decomposed rock
Sound Rock (TCR > 50%) Cast-in place Box PERMANENT SLURRY WALLS FOR STATION BOX Typical East Design Profile
Fill
Organics Silty sand Varv ed Silt and Clay
Typically: 1. Water level maintained 2ft below bottom of excavation 2. Required factor of safety for bottom failure is 1.2 3. Hydrostatic pressure imposed for 25ft below water level below excavation in varved silt/clay Typical Slurry Wall Panel
• 42 inches thick 20 feet long • Maximum depth 100 feet • Water Stop between Panels • Couplers for mezzanine and roof slabs PERMANENT SECANT PILE WALLS AT ANCILLARY BUILDING 1 PERMANENT SECANT PILE WALLS AT ANCILLARY BUILDING 2 Plaxis Model
Typically: • Roof and base slab are fixed; mezzanine slab is pinned BttBottom 5ft 5ftf of sl urry wall lli is unre ifinforce d • Building loads are applied 10ft beloground surface at basement level Wall Deformations
West Wall Deflection East Wall Deflection
120 120 110 Stage 10: Excav to EL. 56.5 Long term 110 100 Stage 17: Backfill to G.S. 100
90 90 Stage 19: Apply LL+SDL on Roof, Mezz Bottom of 80 80 Stage 21: Long term K0 Condition EtiExcavation 70 70
60 60
50 50 levation (ft) levation (ft) E 40 E 40
30 30
20 20
10 10 -1 -050.5 0 050.5 1 151.5 2 252.5 3 353.5 4 454.5 5 -5 -454.5 -4 -353.5 -3 -252.5 -2 -151.5 -1 -050.5 0 050.5 1
Wall Deflection (in) Wall Deflection (in) Bending Moment Diagram
West Wall Bending Moment East Wall Bending Moment 120 120
110 Excavation Excavation 110 Side Side 100 100
90 90
80 80 Stage 10: Excav to EL. 56.5
70 70 Stage 17: Backfill to G.S.
Stage 19: Apply LL+SDL on 60 60 Roof, Mezz
tion (ft) Stage 21: Long term K0 50 ation (ft) 50 aa Condition vv Stage 22: Unbalanced, East K0 40 40 Ele
Elev Stage 23: Unbalanced Pressure 30 30 - West K0 Envelope 20 20
10 10 -800 -600 -400 -200 0 200 400 600 800 -800 -600 -400 -200 0 200 400 600 800
Working Bending Moment (kips-ft/ft) Working Bending Moment (kips-ft/ft) Shear Force Diagram
West Wall Shear Force East Wall Shear Force
120 120 Excavatio Excavatio 110 n Side n Side 110
100 100
90 90
80 80
70 70
60 Stage 10: Excav to EL. 56.5 60
Stage 17: Backfill to G.S. ation (ft) ation (ft) vv 50 vv 50 Stage 19: Apply LL+SDL on Roof, Mezz
Ele 40 Stage 21: Long term K0 Condition Ele 40
Stage 22: Unbalanced, East K0 30 30 Stage 23: Unbalanced Pressure -West K0 20 20 Envelope
10 10 -80 -60 -40 -20 0 20 40 60 80 100 -80 -60 -40 -20 0 20 40 60
Working Shear Force (Kips/ft) Working Shear Force (Kips/ft) Ground Displacements
Vertical Movement 10ft Below Ground Surface
0.5
0.0 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120 140 160 )) -0.5
-1.0
Settlement from wall installation al Movement (in al Movement cc -151.5 Hor izont al M ovement 10ft Be low Groun d S urf ace T oward s Bottom of Excavation (w/o movement by Excavation wall install) Verti 1.0 Bottom of Excavation -2.0 (with movement by wall install) 0.8 End of Construction (w/o movement by -2.5 wall install) 0.6 Left Wall Right Wall ) X (ft) nn 0.4
0.2
0.0 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120 140 160 -0.2 tal Movement tal Movement (i nn -0.4 Bottom of Excavation -0.6 Horizo End of -0.8 Construction
-1.0 Left Wall Right Wall X (ft) Jet Grouting for Excavation Support Plaxis Model Wall Deformation
South Wall Deflection North Wall Deflection
120 120
110 110
100 100
90 90
80 80
70 70
60 60 Elevation (ft) Elevation 50 Stage 13: Excav to EL. 61 (ft) Elevation 50
40 40 Stage 15: Excav to EL. 42.5 30 30
20 Stage 19: Remove S5 20
10 10
0 0 -1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 -5 -4.5 -4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 -10 -10
Wall Deflection (in) Wall Deflection (in) Bending Moment Diagram
South Wall Working Bending Moment North Wall Working Bending Moment
120 120 Excavation 110 Side Excavation 110 Side 100 100
90 90
80 80
70 70
60 60
Elevation (ft) Elevation 50 50
Elevation (ft) Elevation Stage 13: Excav to EL. 61 Stage 13: Excav to EL. 61 40 40 Stage 15: Excav to EL. 42.5 30 Stage 15: Excav to EL. 42.5 30
20 20 Stage 19: Remove S5 Stage 19: Remove S5 10 10 Envelope Envelope 0 0 -400 -300 -200 -100 0 100 200 300 400 -400 -300 -200 -100 0 100 200 300 400 -10 -10
Working Bending Moment (kips-ft/ft) Working Bending Moment (kips-ft/ft) Shear Force Diagram
South Wall Working Shear Force North Wall Working Shear Force
120 120
110 Excavation Excavation 110 Side Side 100 100
90 90
80 80
70 70
60 60
Elevation (ft) Elevation 50 50 Elevation (ft) Elevation
40 Stage 13: Excav to EL. 61 40
30 Stage 15: Excav to EL. 42.5 30
20 Stage 19: Remove S5 20
10 Envelope 10
0 0 -60 -40 -20 0 20 40 60 80 -80 -60 -40 -20 0 20 40 60 -10 -10
Working Shear Force (Kips/ft) Working Shear Force (Kips/ft) Ground Settlement Contours - XDISP Underpinning 1802 2nd Avenue
Basement Predicted Ground Settlements
Micropile elastic shortening settlement Underpinning Using Micropiles Micropile Detail
• Working Load = 250 kips • Casing: 9-5/8ins OD 0.545ins thick, Fy = 80ksi • Reinforcing bar: 2.5ins diam Dyygwidag Threadbar, Fu = 250ksi • Grout: 5000psi • Centralizers at 10 ft c/c • Steel plate w/ nut: 18ins x 18inx 2ins thick, Fy = 50ksi • RkRock soc kt85iket: 8.5ins diam, 9ft long • Bond strength: 200psi Test Pile Sister bar strain gages levation, ft EE Tension Load Test
Movement Symbol Measurement Location
Reinforcement Bar
Steel Casing
Movement Symbol Measurement Location
Reinforcement Bar
Steel Casing
Strain Measurements
Strain Gauge Strain Gauge Symbol Strain Gauge ID Symbol Strain Gauge ID Elevation, ft Elevation, ft
SG1 +1054.3 SG1 +1054.3
SG2 +69.3 SG2 +69.3
SG3 +32. 3 SG3 +32. 3
SG4 +24.3 SG4 +24.3
SG5 +21.3 SG5 +21.3
Pile Load Distribution
Head % De si gn Applied Net Upward Symbol Load Load, kip Movement, in
25 39 0.11
50 99 0.26
75 162 0.41
100 228 0.57
125 290 0740.74
150 348 0.92
175 409 1.12
200 471 1.39
Rock Socket Bond Resistance
fsu = 315.8 psi
Side Elevation Symbol Resistance, Pile Interface Range, ft ksf
+21.3' to 24.3' 45.48 Grout-Bedrock
+24.3' to +27.1' 6.99 Grout-Bedrock fs,max = 46.5 psi Jet Grouting Trial
Trial Site
Existing Lexington Ave /63rd St Station Existing Tunnel
72nd St Station 86th St Station 96th St Station Jet Grouting Trial Site treet reet tt SS S th th 97 96
2nd Avenue Jet Grouting Trial Site Soil Stratification at Jet Grouting Trial Site
Standard Penetration Test, N (blows/0.3m) 0 5 10 15 20 0.0 Fill WtWater T Tbl27able 2.7m 5.0 5.5m Organics 7.6 10.0 Silty Sand 15.0 17.7m epth (m)
DD 20. 0
Varved 25.0 Fill Silt Organics 30.0 Silty Sand Varved Silt 35.0 Jet Grouting Trial Program TC10
Target 2.1m – Double fluid Target 1.5m – Single Fluid TC04 TC06 TC01
1.6m c/c Solid circles denote typical continuous test col umns installed through all soil layers TC02 TC07
TC03 TC08 TC05
Target 1.2m diameter Clear circles denote 1.8m thick grout slab installed in varved silt TC09 Continuous Test Columns (TC01, TC09 and TC10)
Nozzle diameter = 6.0 mm Monitor diameter = 89 mm Rod diameter = 140 mm Lift step = 4 cm
Interlocking Test Columns (TC02, TC03, TC04, TC05, TC06, TC07, TC08)
Nozzle diameter = 6.5 mm Monitor diameter = 89 mm Rod diameter = 140 mm Lift step = 4 cm Continuous Test Columns - Jetting Parameters
Grouting depth Grout Grout Air Rotation Lift speed Test Soil Type Pressure Flowrate Pressure speed Column m bar l/min bar rpm sec/step TC01 Fill 3.08 to 4.60 215 240 10 6.6 10 TC01 Organics 4.60 to 7.60 140 190 10 2.3 29 TC01 Silty Sand 7.60 to 17.80 240 250 10 6.6 10
TC01 Varved Silt 17.80 to 26.72 315 290 10 4.4 15
TC09 Fill 3.05 to 4.60 220 250 10 4.4 15
TC09 Organics 4.60 to 7.60 143 200 10 3.0 42
TC09 Silty Sand 7.60 to 17.80 265 270 10 4.8 14
TC09 Varved Silt 17.80 to 27.18 325 305 10 5.8 22
TC10 Fill 3.49 to 4.60 255 260 0 7.5 16 TC10 Organics 4.60 to 7.60 170 210 0 4.3 42 TC10 Silty Sand 7.60 to 17.80 275 270 0 7.5 16
TC10 Varved Silt 17.80 to 27.70 390 320 0 5.5 22 Interlocking Test Columns - Jetting Parameters
Grouting depth Grout Grout Air Rotation Lift speed Test Soil Type Pressure Flowrate Pressure speed Column m bar l/min bar rpm sec/step TC08 Varved Silt 20.70 to 22.88 245 365 13 6.3 19.0
TC04 Varved Silt 20.72to 22.86 245 365 13 6.1 19.3
TC03 Varved Silt 20.16 to 22.86 250 365 12 6.2 19.1
TC06 Varved Silt 20.68 to 22.86 250 365 12 6.3 19.1
TC05 Varved Silt 20.72 to 22.88 255 365 13 6.5 19.4
TC07 Varved Silt 20.71 to 22.96 250 365 12 6.4 19.4
TC02 VdVarved Silt 20. 72 to 22. 96 245 365 12. 5 616.1 19. 2 In Situ Column Diameter Measurement (Cyljet(Cyljet)) Frappin and Vernhes (2011) In Situ Column Diameter Measurement( (Cyljet(Cyljet)) Frappin and Vernhes (()2011)
Multi-conductor cable connected to regularly spaced current-injecting electrodes and receiver electrodes lowered into a slotted PVC pipe inserted into jet grou t colu mn In Situ Column Diameter Measurement (Cyljet(Cyljet)) Frappin and and Vernhes Vernhes (2011) Soft Computer simulation sandy (2011) clayey to match field silt iso-resistivity 1.6m contours
1.3m Actual Column Shape
Loose silty sand
1.5m
Electr ica l res istance World Trade Center –Cyljet Measurements Crockford et al. (2008) et al. (2008) 2nd Ave Subway - Test Column TC01 2nd Ave Subway - Test Column TC09 2nd Ave Subway - Test Column TC10 Cyljet Measurements – Summary Results Distance from Column Centerline (mm) -2000 -1500 -1000 -500 0 500 1000 1500 2000 0 Fill 5 Organics 10
Silty Sand 15 pth (m) ee D 20
Varved Silt 25 TC01
TC09 30 TC10
35 Sppgyecific Energy for Grout Jet Tornaghi (1989) ⎛ P Q ⎞ ⎜ g g ⎟ Esg = 0.1⎜ ⎟ ⎝ Ls ⎠
Total Specific Energy Es = Esg + Esa Specific Energy for Air Jet
0.29 0.035Qa [(10Pa ) −1] Esa = Ls Pg = Grout pressure (MPa) Qg = Grout flowrate (l/min) Pa = Air pressure (MPa) Qa = Air flowrate (l/min) Ls = Lift spp(eed (cm/min ) Diameter Based on Cyljet Measurements
TC01 - Fill 3000 TC01 - Organics
2500 TC01 - Sand
TC01 - Varved Silt
eter (mm) 2000 Tar get 21 00mm mm (TC01/TC09) TC09 - Fill
1500 TC09 - Organics Target 1500mm (TC10) TC09 - Sand
olumn Dia 1000 TC09 - Varved Silt
500 TC10 - Fill
stimated C TC10 - Organics
EE 0 0 25 50 75 100 125 150 TC10 - Sand
Total Specific Energy (MJ/m) TC10 - Varved Silt Diameter Based on Grout Consumption
TC01 - Fill TC01 - Organics 4000 TC01 - Sand TC01 - Varved Silt ) 3500 TC09 - Fill 3000 TC09 - Organics TC09 - Sand Target 2100mm
meter (mm 2500
aa (TC01/TC09) TC09 - Varved Silt 2000 TC10 - Fill TC10 - Organics 1500 Target 1500mm TC10 - Sand Column Di (TC10) dd 1000 TC10 - Varved Silt TC08 - Varved Silt 500 TC04 - Varved Silt
Estimate 0 TC03 - Varved Silt 0 50 100 150 TC06 - Varved Silt Total Specific Energy (MJ/m) TC05 - Varved Silt TC07 - Varved Silt TC02 - Varved Silt TC10 Coring Locations TCR 98.3% TC04 TC01 TC06
1.6m c/c typical TC02 TCR 92.5% TC07
TC03 TC08 (D = 2754mm) TC05 (D = 2173mm) C1 TCR 95%
TC09 CONSTRUCTION Geotechnical Exploration Program
Utility Relocation
Installation of Secant Pile Wall
Installation of Slurry Wall
Installation of Temporary Roadway Decking
• Steel Beams • Spliced at center • Supported on SOE Walls • Precast Concrete Deck Panels Installation of Temporary Roadway Decking Completed Decking with Traffic Under the Deck Hanging Utilities Excavation in Shallow Rock Drilling and Blasting in Rock Secant Pile Wall Toe Anchors in Rock
Slurry Wall Couplers Hard Rock Tunnel Boring Machine
Construction Shafts at 69th and 72nd Streets StreetStreet StreetStreet StreetStreet StreetStreet StreetStreet ndnd thth thth rdrd stst 99 00 22 11 33 7777 6666 7777 77 77
72ND STREET 69TH STREET SHAFT SITE SHAFT SITE Starting Tunnels at Launch Box Starting Tunnels TBM Tunneling Hopper Loading Truck Steel Ribs PVC Waterproofing Membrane Cast in Place Lining TBM Breakthrough Enlargement of TBM Bore at Turnout Cavern 72nd St Cavern - Top Heading 72nd St Cavern – Top Heading Complete Thank You