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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