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US Army Corps of Engineers

BUILDING STRONG®

Wolf Creek Dam Barrier Wall Construction

Mr. Brook Brosi, PG

US Army Corps of Engineers

Mr. Lyndon Bedford & Mr. Pablo Bassola

Treviicos-Soletanche Joint Venture

DFI Slurry Wall Seminar

June 27, 2013

OUTLINE

INTRODUCTION

FOUNDATION PROBLEMS & PHOTOS

1970’s GROUTING & WALL CONSTR.

SETUP FOR BARRIER WALL CONSTR

5-STEP BARRIER WALL CONSTRUCTION

CONCLUSIONS

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INTRODUCTION

Wolf Creek Dam

Largest manmade reservoir east of the Mississippi River. Located in central-southern Kentucky. Produces $77,000,000-per-year in

hydropower for treasury (2006). Designed in the 1930’s, built mostly in

1940’s, Powerhouse completed in 1952.

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Location of Site

Wolf Creek Dam

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Downward Slope of

Cut Off Trench

Cut Off TrenchToe of Compacted Fill

Drainage Blanket

Alluvium and Disposal

Embankment Plan

0 1+00A 2+00A 3+00A 4+00A 5+00A1+00B2+00B3+00B4+00B5+00B

Elev. 773

Cutoff trenchLimestone Bedrock

Dam

Soil Foundation

Pool

Embankment Profile

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Detailed Geology of Site

Source: Kentucky Geological Survey

The Problem with Wolf Creek’s foundation:

KARST

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Foundation Treatment

Cave

Cave

Solution Features

Original Construction

in 1940’s

Original Construction

in 1940’s

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Core TrenchOriginal

Constructionin 1940’s

Approx New WallLocation

Pinnacle

Original Construction

in 1940’s

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Approx New WallAlignment

Original Construction

in 1940’s

Original Construction

in 1940’s

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FOUNDATION PROBLEMSIN 1960’S

Initial Distress Indicators1967 - 1968

SPILLWAY

MUDDY WATERSHOW

POWERHOUSEN

SINKHOLE 3-13-68

SINKHOLE 4-22-68 SINKHOLE8-22-67

SWITCH YARD WET AREAS

Dam Embankment

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Sinkhole

Switchyard

1968 Sinkhole

LATE 1960’S- EARLY1970’SEMERGENCYGROUTING

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1960’s/1970’s Remedial Grouting

Concrete Monoliths

LAKE

RIVERGrout Lines

Solution Features

1960’s and 70’s Remedial Grouting

Concrete Dam

Earth Emb

SwitchyardGrout Lines

Crest Grout Line

Wrap-Around Grout Lines

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Geological Profile showing caves

MONOL ITH

20 ft

Drilling – Grouting Summary

174,666 ft (53,273 m) of overburden drilling

97,032 ft (29,595 m) of rock drilling

290,087 cu ft (8,214.3 m³ ) of injected grout solids.

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1970’S BARRIER WALL CONSTRUCTION

Follow-Up

Two barrier walls installed in Wolf Creek after grouting was completed.

One along Crest

One at down-stream toe

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1970’s Barrier Wall Construction

36”-Rock Drill ICOS Wall

Self-propelled top-drive drill platform

Full-face, roller rock, drill bit

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CURRENT BARRIER WALL CONSTRUCTION

Project Geography

Contractor offices & slurry plant area

Disposal AreaContractor Laydown

USACE Resident office

Power house

Working Platform

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Layout of Wall

• Technique Areas

• Critical Areas

• 3800 linear feet total

THE REQUIREMENTS

Description UnitSpecification Requirements

Barrier Wall Thickness (Minimum) ft 2

Overlap between elements (Minimum) ft 0.5

Concrete strength (Minimum) psi 2000

Permeability (Maximum) Lugeon 3

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WALL CONSTRUCTION SEQUENCE

5-STEP PROCESS

5 – Step Process1. Pre-Grouting (2 lines either side of wall

and intensive grouting in Critical Areas)

2. PCEW (Panel wall embedded to bedrock)

3. Pilot hole drilling (to full depth)

4. Secant pile excavation & Combined barrier wall (to full depth)

5. Verification coring to confirm quality (on selected elements)

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Installation of upstream / downstream grout courtain

High mobility grouting (HMG) to treat the rock more than 5 ft below TOR.

Low mobility grouting (LMG) designed to treat the rock, soft zones of soil, and weathered rock.

2,000 grout holes, most 325 ft deep.

Over 1,000,000 gallons of grout (3.7million liters).

Composite Grout Programs

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Dam Remediation Methodology• 3,800-l.ft Barrier Wall

• 550,000 sq.ft Protective Concrete Embankment

Wall (PCEW)

• 910,000 sq.ft Barrier Wall

• Max depth 275-ft

Protective Concrete Embankment Wall (PCEW)

Construction of a 6-ft wide concrete wall from a working platform to a minimum of 2-ft below the top of the rock.

Installation of 433 primary and secondary concrete panels.

Approx. 550,000 sq.ft of Protective Concrete Embankment Wall (PCEW).

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PCEW Sequence

Embankment

Rock

P

P P

5” min overlap

SP

S

9’-2”

6 ft

Hydromill – With Rock Teeth in Rock

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PCEW Deviation Monitoring

Onboard instrumentation allows for real time monitoring of panel verticality and twist during excavation

Panel report confirms panel position in relation to theoretical

Directionally Drilled Pilot Holes

Installation of 8-inch diameter directionally drilled pilot holes (DD), through the PCEW and full depth into the rock reaching up to 282 ft depth.

Served as a guide for the installation of the secant piles with minimal deviation.

Allow for additional investigation of concrete/rock conditions below the top of the rock.

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DRILL 8” Ø GUIDE/EXPLORATORY HOLES

Embankment

Rock

31”

•Drill 8” Ø guide/exploratory hole through PCEW

•Guide/verticality control for secant pile

•Investigate rock condition at pile location, grout if conditions dictate

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DD – Overlap AnalysisSimulation of primary and secondary piles following pilot holes.

– Starting point for pile installation

DD – Deviation Charts* More than 70% of the pilot holes installed reached a maximumdeviation of 2 to 3 inches at a depth of 282 ft.

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RCD Secant Piles

Installation of 50-inch diameter secant piles, excavated through the PCEW and full depth into the rock reaching up to a target depth of 273 ft, using a Reverse Circulation Drilling machine.

Sequence of primary and secondary piles.

1,197 secant piles installed, with only two remedial piles required.

PRE-EXCAVATION 50” Ø SECANT PILES

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RCD 50” Ø OVERLAPPING SECANT PILES

Embankment

Rock

31” Min. 2’ Overlap req’d

P PS

Protective Concrete Embankment Wall (PCEW)

Hydromill excavation

Overlapping 6’ x 9’ panels

Number of Panels Complete – 245/431

57% Complete

6

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RCD on board instrumentation

Pile Verticality MonitoringEnparis verticality Final Koden run

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Pile Overlap Analysis

Pile verticality information to produce 3D drawings for geometrical analysis

Pile Overlap Analysis

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Combined Barrier Wall Panels

Installation of a wall using a combination of RCD piles and hydromill excavated panels.

50 Inches diameter piles and 9.2-ft x 2.6-ft CBW panels.

52 combined barrier wall elements were installed during the project.

Combined Barrier Wall Panels

50” dia. piles9.2-ft x 2.6-ft CBW panels

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Wolf Creek Dam at construction peak

Deployment of equipment along the alignment of the barrier wall

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PCEW Panel installation in CA#1

Barrier Wall Pile Installation in CA#1

Primary Piles in Cave and Core Trench AreaSecondary Piles in Cave and Core Trench AreaBarrier Wall installed in Cave and Core Trench Area

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Verification Coring on selected elements

179 verification holes were drilled on selected elements to verify the concrete quality, joint quality, the contact with the underlying rock, and permeability.

Geological log, core photos, televiewersurvey, falling and rising head water test, UCS test were performed to verify quality of the barrier wall.

Concrete / Rock Contact

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Televiewer survey in vertical hole

Televiewer survey showing a joint between primary and secondary piles

Wall Completed!

Last pile placed on March 6th, 2013

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Results Quality:

1,197 piles + 52 Combined Barrier Wall elements installed with only 2 remedial piles, les than 0.2%.

Barrier wall thickness, overlap between elements, concrete strength, and permeability requirements met, if not exceeded.

Schedule:

Construction of the Barrier Wall 11 months ahead of schedule.

Safety:

1.3 million hours without a lost time injury.

Wall Thickness Distribution Piles

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Joint Overlap Distribution Piles

Conclusions

Wolf Creek Dam had serious foundation problems due to Karst

The Corps chose a Cutoff Wall as the permanent foundation repair

Treviicos-Soletache used an innovative method of wall construction

Treviicos-Soletache exceeded the Corp’s requirements for the cutoff wall.

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Thank You for your Attention