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Self‐Hardening Slurry Wall Installation by Hydromill 

at the Herbert Hoover Dike ‐An Innovative Solution

Mario Mauro

TREVIICOS ‐ 38 Third Ave. ‐ Charlestown, MA 02129 ‐ Ph: 617 – 241 4800 – www.treviicos.com

US Army Corps of Engineers – Jacksonville District

Florida DEP

South Florida Water Management District

Deep Foundation Institute

Acknowledgments

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1. Project Background

2. Selection of Cutoff Wall Construction Method

3. Quality Control & Validation

4. Conclusions

Outline of the Presentation

1.Project Background

• Originally constructed by farmers in theearly 1900’s for flood protection

• Two severe hurricanes in the late 1920’scaused massive flooding and loss of life

• The levee system was upgraded in the1930’s

• The levee system was upgraded againafter two more severe hurricanes in the1940’s, for a total of 143 miles.

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Herbert Hoover Dike Construction

• Through the years, the dike has experienced a high degree of seepage under and through the embankment, which could cause a failure of the system

• In 2007 USACE placed HHD on DSAC 1 list of dams with highest priority for action

• Priority Area is Reach 1, 22 mile stretch from Belle Glade to Port Mayaca

Courtesy of USACE

HHD in recent years

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Rehabilitation Concept

Courtesy of USACE

2. Selection of CW Construction Method

IDIQ Contract and performance based specifications

Contractor allowed to select wall installation method provided performance specifications requirements and acceptance criteria were met

Method selected had to be proved in a 500‐ft long demonstration section

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Previous Experience at HH Dike

Factors That Influenced the Selection of Cutoff Wall Construction Method

Variable nature of the ground and rock conditions

Depth of cutoff wall to 80 feet

Need for a reliable wall construction method

Strict acceptance criteria

Need for removal all peat and organic materials along the wall alignment

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Cutoff Construction Approach

Panel construction utilizing Self‐Hardening Slurry (SHS)

SHS is a mixture of water, cementitious material, bentonite and additives

SHS provides support of the open trench during excavation, and later becomes the permanent wall material

Hydraulic and mechanical clamshells to completely remove upper soils including peat, topsoil and miscellaneous fill material

Followed by a Hydromill cutter to excavate to a final depth of about 80 feet through limestone of variable continuity and hardness

SHS Cutoff Wall by Panel Method

• Continuous cutoff wall withoverlapping primary andsecondary panels

• Secondary panels providepartial overlap on each side of theadjacent primary panels ensuringwall continuity.

• Panel verticality is measured inreal‐time during excavation. Ifexcessive deviation occurs, thepanel verticality is corrected.

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Hydromill  System

Desanding Equipment

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Use of the Hydromill with SHS

No previous experience in the US market

Standard Hydromill equipment is not designed for the use with self‐hardening slurry

Wear and tear on the equipment is a challenge, which requires attention

“Desanding” of SHS requires modifications of the standard desanding equipment

Self‐Hardening Slurry (SHS) Plant

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Work Platform and Site Access

Guide Wall Installation

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Clamshell Excavation under SHS

Excavation Equipment

Hydraulic clamshell Mechanical clamshell

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Hydromill Equipment

Hydromill Excavation under SHS

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SHS Cutoff Wall Construction

3. QC Control & Validation

Construction QA / QC testing

Panel verticality (real time monitoring via inclinometer in Hydromill)

Panel width (ea 100 ft) and depth (ea 20 ft) measurements

Panel centerline, locations, joints via GPS

Slurry plant samples (temperature, unit weight, viscosity, UCS and laboratory permeability)

Wet slurry grab samples at three depths (35, 55, 70/75 feet) of wall at 200 foot intervals hardened properties at 7 and 28 days (UCS, laboratory permeability)

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SHS Cutoff Wall ValidationVerification borings: @ 170 /200 ft

Borehole televiewer with inclinometer

In‐situ permeability: <1x10‐6

cm/sec

Strength: 100 psi min to 500 psi max (for 10‐point moving ave.) with no value below 75 psi

Homogeneous and continuous wall

Typical Core Sample

Borehole Televiewer

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In‐situ Permeability (Task Order 3)

1.0E‐10

1.0E‐09

1.0E‐08

1.0E‐07

1.0E‐06

1.0E‐05

Apr‐09 Jun‐09 Jul‐09 Sep‐09 Oct‐09 Dec‐09 Jan‐10 Mar‐10 Apr‐10

Perm

eab

ility (cm

/sec)

CW Acceptance Criteria: In situ permeability lower than 1 x 10‐6

cm/sec

Permeability Lab Testing – Post Placement Samples (Task Order 3)

1.0E‐10

1.0E‐09

1.0E‐08

1.0E‐07

1.0E‐06

1.0E‐05

May‐09 Jun‐09 Jul‐09 Jul‐09 Aug‐09 Sep‐09 Oct‐09 Nov‐09 Dec‐09 Jan‐10 Feb‐10 Mar‐10 Apr‐10

Perm

eab

ility (cm

/sec)

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Strength Testing (UCS) – Panel Joint

UCS testing of Panel Joint (VB‐3)Core Specimen at Panel Joint (VB‐2, 58 ft depth)

Exposed Lakeside of Cutoff WallExposed Top of Cutoff Wall

Visual Inspection of Top of Cutoff Wall

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Performance specifications were the right approach for this project

The innovative use of the Hydromill cutter allowed successfulconstruction of the SHS cutoff wall through heterogeneous materialsand rock (over 7.2 miles, 2.5 M sqft of wall)

The Clamshell/Hydromill SHS construction method provided a cut‐off wall that is homogeneous, continuous and meets strength andpermeability performance criteria

Carefully designed self‐hardening slurry produced good bondingbetween primary and secondary panels and prevented desiccationand cracking of the top of the hardened wall

The hard work and dedication of all TREVIICOS personnel was key tosuccess.

4. Conclusions

TREVIICOS ‐ 38 Third Ave. ‐ Charlestown, MA 02129 ‐ Ph: 617 – 241 4800 – www.treviicos.com