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P R E S E N T E D B Y :
I R A BROTMAN , P E
MOF FAT T & N I CHO LO C T O B E R 1 8 , 2 0 1 2
Marine Prefabricated Vertical Drains for the Craney Island Eastward Expansion
Craney Island Eastward Expansion
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CIEE Layout
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Existing CIDMMA
CIDMMAEast Dike
CIEE Main Dike
CIEE Cross Dike
(typ)
Subsurface Stratigraphy
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CIDMMA Dikes (1954)
CIDMMA Dikes (1954)
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Cross Dike Objectives
Experiences with CIDMMA (built to +5’)
Minimize Mud Waves
Minimize Deformation
Minimize Instability – Now and Future
Minimize Ultimate Sand Volume
Predictable Schedule
Limit Inappropriate Construction Claims
Cross Dike Alternatives
High strength geotextile/geogrid
Pre‐dredge
Deep Soil Mixing
Prefabricated Vertical Drains (PVD) Build dikes in lifts/stages
Allow increase in shear strength
Achieve by specifying lift thicknesses and hold times
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Distance in feet (x 1000)
.50 -0.45 -0.40 -0.35 -0.30 -0.25 -0.20 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
Ele
vatio
n in
fee
t (M
LLW
)
-160
-140
-120
-100
-80
-60
-40
-20
0
20
40
60
Selected Low Cost, Low Risk Cross Dike
Final target elevation = +18 ft (MLLW)
900 ft Wide
Built in 3 Stages
Upper Norfolk Clay (Qnu)
Pleistocene/Pliocene Sands (Qnl/Tys)
PVDs
Hydraulic Sand FillZone of
PVDs
Marine PVDs Marine PVDsLand PVDs
PVD Design
Design for long‐term (20‐30 feet) settlement
Use Dike Lifts for Surcharge Load
PVD Spacing
Constructability Overwater – minimize due to cost
Verticality Control
Production
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PVD Design Parameters
Ref: Bucket Tests by Cortlever, 1983
Long Term Consolidation Settlement Effects Critical
• Buckled Discharge Critical
• ISO/EN Methods for Testing
Ref: EN 15237, 2007
Typical PVD
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Discharge Capacity TestISO 12958 & EN 15237
PVD Test Results – Discharge Capacity
PROPERTY SPECIFIED VALUES TEST RESULTS
# Tests AverageStandard
Deviation
Discharge capacity
ISO 12958 & EN 152370.3 gpm@ 65 psi 22
0.32
gpm0.18
Discharge Capacity
Buckled
ISO 12958 & EN 15237
2.0 gpm@ 35 psi 162.32
gpm1.07
American Wick Drain, Soil Drain 1000
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Construction Sequence
Place Initial Lift
Install Marine PVDs Initiate Strength Gain
Place Second Lift Allow Additional Strength Gain
Place Third Lift
South and Division Cross Dikes
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Cross Dikes – Stage 1
Hydraulic Sand Fill, Stage 1
Cross Dikes Stage 1 – Marine PVDs
PVDs Outer 3rd
PVDs PVDs
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Cross Dikes Stage 2A – Sand Fill
Hydraulic Sand Fill, Stage 2A
Rendering Post Stage 3
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Rendering Southeast Cell Closed
GLDD – Stage 1
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GLDD – Stage 1 – Marine PVDs
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PVD Monitoring - Observational Method
Assess Progress and Validate Strength Grains
Lab Testing
PVD Installation Records 12 MLF of PVDs Installed
100,000 Individual PVDs
To depths over 130 ft
Avg 500 PVDs / day
Surveys
In‐situ Testing
Geotechnical Instrumentation
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PVD Installation Record
PVD Tip Elevations
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Multibeam Survey
Multibeam Survey
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Geotechnical Instrumentation
Instrumentation Website
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Settlement
Inclinometer
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Summary
Contractor Innovation Spillbarge
Specialized Barge
Positioning /Tracking System
Observational Method Success QA of PVD testing
PVD installation verification
Measure behavior of foundation during filling
Validate Lift placement schedule and hold times
Control project risk
Thank You
Special thanks to:
Virginia Port Authority
Corps of Engineers, Norfolk District