Evolution of Seepage Barrier wall Contracts US Army Corps ... · PDF fileEvolution of Barrier...

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“The views, opinions and findings contained in this report are those of the authors(s) and should not be construed as an official Department of the Army position, policy or decision, unless so designated by other official documentation.”

Georgette Hlepas, PhD, PEGeotechnical EngineerDam Safety Mandatory Design Center of Expertise, USACE

Vanessa C. Bateman, PE, PGChief, Civil Design BranchNashville District, USACE

AEG Annual Meeting24 September, 2016

1File Name

Evolution of Barrier Wall Contracts:US Army Corps of Engineers

2

… Or, How Lessons Learned on one project inform how you approach the next one

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Wolf Creek Dam1974-1978

Beaver Dam1980s

Addicks and Barker1982

Mud Mountain1988-1990

McAlpine L&D1994

Walter F. George2001-2003

West Hill2001-2002

Mississinewa2002-2005

Wolf Creek Dam2010-2013

Center Hill Dam2012-2015

Bolivar Dam2014-2016

East Branch Dam2014-Present

USACE Barrier Walls over Time

Work PlatformCutoff Wall

Bedrock

Foundation Soil

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USACE Typical Wall Configuration

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USACE Evolution

Prescriptive PerformancePerformance-ish

Contract Methodology

?

Wolf Creek 1974-78

Wolf Creek 2010-2013

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USACE EvolutionContract Methodology

Build a Secant Wall

• Dimensions• Backfill• Verification• Means and Methods

Primary Element

Secondary Element

Build a Wall

or

or

Propose:Means and Methods

• Min Dimensions• Min Backfill properties• Verification

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Typical Section

Wolf Creek 1974-78

1. RFP Sent2. Selected Contractor Proposals3. Prescriptive Spec Written

Presenter

Presentation Notes

Several proposals were evaluated. This was selected as the best technically. It was a cutting edge approach and the world record holder for many years.

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Wolf Creek 1970’s Construction

PCEW - Hydromill

Rock

P

P P

5” min overlap

SP

S

9’-2”

6 ft

Cavity

Wolf Creek 2010-2013 Construction

Embankment

Alluvium

PLAN

PROFILE

Presenter

Presentation Notes

The encasement wall is constructed with the hydromill and consists of interconnected panels. The encasement wall is intended to isolate/protect the embankment from the subsequent wall construction. With some of the limestone exceeding 30,000 psi compressive strength, there is potential for excavations to be under construction for extended periods of time. So, we liked the idea of an encasement wall to limit the amount of time the embankment is exposed. The encasement wall mitigates this concern.

35”

Pilot Hole – Wassara Water Hammer

PLAN

PROFILE


Embankment

Rock

Alluvium

Presenter

Presentation Notes

After a section of encasement wall has been completed, we start drilling pilot holes to 3-ft below the design depth of the wall. The purpose of these holes is not only to guide the subsequent wall construction, but to treat any anomalies encountered before we subject the features to massive volumes of slurry. In the Technique Areas, we started drilling these holes on 31-inch centers which resulted in a ~35-inch thick wall on average (11-inches thicker than the 24-inch spec requirement). The pilot holes are drilled with the Wassarra Water Hammer, which utilizies a slant face bit and a bent housing to steer the boreholes. The capability of steering all this equipment is a significant advancement from the old days.

Rock

31”

Min. 2’ Wall Thickness

Alluvium

Embankment


Presenter

Presentation Notes

Once we have installed the pilot holes, now we can start constructing the actual barrier wall and our contractor proposed three technicques. The first type of wall configuration I will discuss is the pile barrier wall, which consists of overlapping piles constructed with the WIRTH assembly equipped with a stinger to follow the pilot hole. The WIRTH assembly has limited steering capabilities; however, you can always increase the size of the excavation if deviation is out of tolerance or another pile can be installed.

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USACE EvolutionDemonstration Sections

…but maybe not in the critical part of the wall?

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Pre-grouting?Grouting in 2 Contracts Grouting in 1 contract

Add Grout Line along platform from WOL or CEN

Upstream Grout LineAngled at 15° toward the right

24’


2 Contracts2 Contracts with IDIQ1 ContractNo pre-grouting

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USACE EvolutionTechnology Improvements

Verification Methods

Sensor Unit

25˚

Plum Bob

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USACE EvolutionVerification Methods

There are multiple methods to measure excavation

This one works great…for circular holes

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Need more than one methodBut three can be overkill.

Measure excavation dimension, verify with neat-line tools

PPP

PP

P

P

ÎÎ

Î

ÎÎP

PP

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Core Drilling remains important

Color in Concrete makes it easy to see good joints

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Impermeable??


Cigarette Butt??

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BUILDING STRONG®

Deficiency

OPTV: Invaluable Information

Core Loss


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USACE Evolution

Lorem Ipsum QA Report 1974

Changes in Data Management

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USACE EvolutionChanges in Data Management

+ 36 GB Files

144

ft


Paper!?

Database

GIS Maps Files on the servervs

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Compressive Strength (psi)

2000 psi Requirement

12,811 cylinders

USACE EvolutionChanges in Data Management = EASIER!

Presenter

Presentation Notes

28 day strength test data is normal, with all average element strengths above 2000 psi minimum compressive strength requirement

PBW Continuity Statistics - Koden

Dimension Min (ft) Max (ft) Avg (ft) Spec (ft)Thickness 1.95 4.4 3.2 2.0Overlap 0.5 3.8 1.5 0.5

0 1 0 2 13 22 39 66 104200

385

550

764

1090

13551476

1197

914

651

427

19782 60 36 21 17 4 0

0.0%

2.0%

4.0%

6.0%

8.0%

10.0%

12.0%

14.0%

16.0%

18.0%

1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 4.3 4.4 4.5PBW Wall Thickness (feet)

Minimum Wall Thickness = 2'

9674 Measurements on 1197 Piles1 Measurement less than 2-ft

99.99%


Presenter

Presentation Notes

Histogram doesn’t reflect the min wall thickness (i.e. 22.8 inches), but I will update the histogram once we receive an updated spreadsheet.

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Analyze


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CommunicateLessons Learned

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USACE Evolution (or not)

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Change with Technology

Plum Bob& Paper

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Questions?

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