Jacob Chacko/Mike Kapuskar

1
Jacob Chacko/Mike Kapuskar

• Fugro-Earth Mechanics Joint Venture

2
SUSPENSION SPAN

• Geotechnical and Foundation Installation
  Considerations

3
Main Span - Geotechnical Explorations
4
Main Span - Surface Conditions (Schematic)
5
Main Span - Subsurface Conditions
6
Main Span - Longitudinal Section
7
Top of Franciscan Formation Bedrock
8
Thickness of Young Bay Mud
9
East Pier Foundations

• Footing
• Structural Steel Frames encased in Concrete
• Two Connected Octagonal Units
• 8 Piles per Unit
• Piling
• 106-meter long, 2.5-meter dia CISS Piles
• Piles are Vertical
• Concrete infill down to El. -54 meters
• Steel Shell wall thickness - 85mm to 45mm

Footing Layout TBA
10
East Pier Area - Transverse Section
11
UAM Paleochannel Sand
Thickness of Sand Layer
Top of Sand Layer
12
Axial Pile Capacity- Pier E2-Westbound
13
East Pier Construction Considerations

• Construction Issues
• Presence of 15 to 20 meters of Soft Near-surface
  Young Bay Mud
• Setup of Pile Capacity
• Increase in Soil Resistance to Driving during
  Delays
• May require Waiting Period prior to Application
  of Construction Loads
• Piles to be Driven through Dense Sand Layers
• Piles to be Tipped in Bedrock
• Key Special Provisions
• Requirement for a 1700 kJ primary Hammer
• Piles to be PDA monitored to
• Verify Satisfactory Hammer Performance and
• Reduce potential for Overstressing the Pile
• No Minimum Blow Count Requirement at Specified
  Pile Tip Elevation
• Piles driven to Specified Tip Elevation (or piles
  encountering Refusal with Satisfactorily
  performing hammer within 10-meters of Tip
  Elevation) to be Accepted

14
PIDP Results - Soil Resistance to Driving

• SRD values in Clay are less than Predicted Design
  Capacity
• SRD values can be predicted using published
  Methods
• Measured SRD Values for Continuous Driving
  Generally correspond to Coring Case Predictions
• Increased SRD during interruptions as Pile Setup
  Occurs

15
PIDP Results - Blow Counts

• With Adequate Hammers Piles can be Driven
  (continuously) to Required Tip Elevations with
  Reasonable Blow Counts
• Increased Blow Counts observed during
  interruptions
• Measured Blow Counts for Continuous Driving
  Generally agree with Coring Case Predictions

16
Soil Resistance to Driving - Pier E2-Westbound
17
Predicted Blow Counts
Menck - MHU 500
Menck - MHU 1700
18
Tower Foundations

• Footing
• Octagonal Footing Layout
• 12 perimeter and 1 center Piles
• Pilecap is 22½ x 24 meters
• Piling
• Piles to be supported in Franciscan Bedrock
• Piling to be Unsupported down to El. -22 meters
• 2.5-meter dia. Permanent Steel Shell down to El.
  -30 meters
• 2.2-meter diameter rock socket below El. -30
  meters
• Total length of pile is 68 to 77 meters
• Rock sockets are 46 to 55 meters

19
Tower Foundations

• Piling
• Piles to be supported in Franciscan Bedrock
• Piling to be Unsupported down to El. -22 meters
• 2.5-meter dia. Permanent Steel Shell down to El.
  -30 meters
• 2.2-meter diameter rock socket below El. -30
  meters
• Total length of pile is 68 to 77 meters
• Rock sockets are 46 to 55 meters

20
Pylon Area - Longitudinal Section
21
Pylon Area - Bedrock Surface
Top of Intensely Weathered Rock
Top of Slightly Weathered Rock
22
Thickness of Weathered Bedrock
23
Thickness of Fill in Cove Area
24
Pylon Area - Transverse Section
25
Pylon Construction Considerations

• No Blasting allowed in Project Permits
• Sloping Bay Floor and Bedrock Surfaces
• Piles to be Drilled through Variable Rock
  Conditions including
• Rock Fragments and Intensely Weathered Rock (may
  cave)
• Hard Fresh rock with qu gt 70 MPa
• Presence of Very Soft Clay Fill Near the Surface
• Temporary Casing to return Drilling
  Fluids/Cuttings to the Surface
• Requirement for Pile to be Unsupported Above El.
  -22 meters

El. -22
El. -30
26
West Pier Foundations

• 19-meter square, 10 meter thick Footings founded
  in Franciscan Bedrock
• Base of Footings - El. -4 to -6 meters
• Westbound Footing over Steep Slope
• Footing embedment of 9 to 26 meters (30 to 85
  feet)
• Design may include 10-meter long CIDH piles
  beneath Westbound Footing
• Footings to be Cast against Undisturbed Rock

27
TRANSVERSE SECTION (West Pier W2)
28
West Pier Construction Considerations

• Steep (45 - 55 degree) Ground Surface Slope at
  Westbound Footing
• Deep Excavations (up to 26 meters) into Very Hard
  Sandstone (qu gt 70 Mpa) required for Footing
  Construction
• Blasting not Allowed in Project Permits
• Temporary Rock Slope Stabilization likely
  Required During Construction
• Potential for Seepage of Ground Water into
  Excavation (Packer Test Data are available for
  Design of Dewatering Facilities)

29
Main Span - Temporary Towers

• Design and Construction Issues
• Tower Locations depend on Construction Sequence
• Tower Design by Contractorbased on geotechnical
  information and design criteria from Caltrans
• Presence of Torpedo House
• Variable Surface/Subsurface Conditions

30
YERBA BUENA ISLAND

• GEOLOGY
• FOUNDATIONS
• CONSTRUCTION ISSUES

31
YERBA BUENA ISLAND - Geology
32
Northeast Point Hill (North Side)
33
Northeast Point Hill (South Side)
34
Northern Saddle Area
35
Tunnel Approach Slopes (North Side)
36
Tunnel Approach Slopes (South Side)
37
YBI GEOLOGY

• Variable Terrain Subsurface Conditions
• Soil Rock Slopes
• Competent Soils, Hard Rock
• Extensive Soil Data
• (53) Soil Rock Borings 1,830 m, (17) CPT
  300m
• P-S Logs, Video Logs, Pressuremeter, Packer Tests
• Seismic reflection surveys, geologic mapping
• Laboratory strength tests
• Addl holes from 2 prior Caltrans SR Projects
• (2) YBI Site Characterization Reports

38
LOG OF TEST BORINGS
39
YBI GEOLOGY

• Major Geologic Units
• GRANULAR FILLS, up to 10m (af)
• w/ gravel, cobbles/boulders in USCG
• SEDIMENTARY ALLUVIUM, up to 40m (Qs/Qal/Qb)
• competent silty sands, some sandy silts clays
• LANDSLIDE DEBRIS (Qls, Qols)
• TRANSITION, decomp. rock/hard sandy clay, upto 5m
  (Qbr)
• BEDROCK, graywacke sandstone interbedded w/
  siltstone/claystone (JKf)

40
YBI GEOLOGY
Fresh Rock
Weathered Rock
41
YBI GEOLOGY
Bedrock and Groundwater
42
YBI GEOLOGY
WB TRANSITION ALIGNMENT
43
YBI GEOLOGY
EB DETOUR ALIGNMENT
44
YBI GEOLOGY
BENT W4
45
YBI GEOLOGY
BENT W5
46
YBI FOUNDATIONS

• Permanent Foundations
• (25) large ftgs w/ 80-150T W360x237 HP360x132
  piles 15-20 m
• (5) very large spread footings on rock
• (2-3) ftgs w/ 2.4/2.5 m CIDH Shafts in soil
  rock upto 10 m

47
YBI FOUNDATIONS

• Temporary Foundations
• (38) spread footings on soil or rock
• (50) 30-110T HP360x132 x108 piles 12 m
• (6) 16 OD Pipe piles lt 8 m
• 60-ton tiedowns at some footings
• (3) 24 dia. CIDH (w/ cantilever steel pipe ext.)

48
YBI FOUNDATIONS

• Viaduct modifications
• (11) spread footings on soil w/ tiedowns
• (1) Footing on HP360x108 piles
• (5) Concrete shear key blocks under exist. walls

49
YBI FOUNDATIONS

• Temporary excavation at Bent 48
• (2) Exist. ftgs underpinned (chemical grouting)
• Requires careful settlement monitoring,
• Hydraulic conductivity tests,
• Core extraction for qu testing
• (2) Temp. tieback walls w/ CIP conc. facing
• 15-ton anchors thru grouted blocks and
  pilegroups

50
YBI FOUNDATIONS

• New retaining wall (Southgate Rd relocation)
• Exist. retaining walls remove/reconstruct
• New utility trench

51
CONSTRUCTION ISSUES
Variable Soil,Rock Groundwater Conditions
52
CONSTRUCTION ISSUES
       


Steep, Vegetated Slopes at EB2 EB3


   
   
1974 LANDSLIDES AT USCG SLOPES NOW RETAINED AND
REGRADED
SLIDE 98C
53
CONSTRUCTION ISSUES

• Slope access?
• Shoring
• Install 80-110T HP360x or
• or 16 OD pipe piles w/ tiedowns
• Build pedestal footings, partially exposed
• or embedded w/ slurry backfill

54
OTHER CONSTRUCTION ISSUES

• Challenging Site Access
• Nearby Archael./Historical Sites, Buildings
• Cobbly Fills _at_ USCG
• Rock Excavations
• Exist. Underground Utilities