Dam Safety DamBreakModeling

8/17/2019 Dam Safety DamBreakModeling

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2015 National Dam Safety Program Technical Seminar No. 22:

Dam Breach Modeling

and Consequence Assessment

Overview of Failure Modes

Jay N. Stateler


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Embankment

Dams

Foundation Soil

Foundation Soil

Earthfi ll Zones

Filters

Riprap

Slope

Protection

Grout Curtain

Toe

Drain

Foundation Rock

Riprap

Slope

ProtectionEarthfill


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Potential

Failure Mode

Foundation Soil

Foundation Soil

Earthfi ll Zones

Filters

Riprap

Slope

Protection

Grout Curtain

Toe

Drain

Foundation Rock

Riprap

Slope

ProtectionEarthfill

• Seepage through

dam

• Erodes earthfil l

• Carries earthfilldownstream

• Eventually

breaches dam


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Hadlock Pond

New York

Constructed: 1896

Modified: 2004-2005

Failed: July 2, 2005

Seepage Failure0 Fatalities


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Baldwin Hills Dam

Los Angeles, California

Constructed: 1947-1951

Failed: December 11, 1963

Seepage Failure

5 Fatalities


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San Francisco Dam

New Mexico

Constructed: 1960’sFailed: May 24, 2003

Flood – Seepage Failure

No Fatalit ies


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Delhi Dam, Iowa

Constructed: 1929


Flood – Some overtopping,

but failed due to seepage

0 Fatalities


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Potential

Failure Mode

Foundation Soil

Foundation Soil

Earthfi ll Zones

Filters

Riprap

Slope

Protection

Grout Curtain

Toe

Drain

Foundation Rock

Riprap

Slope

ProtectionEarthfill

• Seepage through

dam

• Erodes earthfil l

• Carries earthfilldownstream

• Eventually

breaches dam

• Filter lets waterthrough, but not

earthfil l carried by

seepage

• Stops failure mode

development


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Potential

Failure Mode

Foundation Soil

Foundation Soil

Earthfi ll Zones

Filters

Riprap

Slope

Protection

Grout Curtain

Toe

Drain

Foundation Rock

Riprap

Slope

ProtectionEarthfill

• Seepage through

foundation soil

• Erodes soil

• Carries soil to a

downstream exit

point

• Eventually creates

a dam breach


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20 feet high

Arthur V. Watkins DamConstructed: 1958-1964

Nearly Failed: November, 2006

Seepage

Foundation soi l

deposits in SouthDrain


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Potential

Failure Mode

Foundation Soil

Foundation Soil

Earthfi ll Zones

Filters

Riprap

Slope

Protection

Grout Curtain

Toe

Drain

Foundation Rock

Riprap

Slope

ProtectionEarthfill

• Seepage through

foundation soil

• Cutoff trench, grout

curtain, cutoff wall,

etc. limit seepage

through foundation

• Downstream fil ters

and toe drain collect(and fi lter seepage)

• Potential for failure

mode development

is reduced

Cutoff Trench


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Potential

Failure Mode

• Seepage carries

earthfi ll into

foundation

• Erodes earthfil l• Carries earthfill

downstream

• Eventually breaches

dam

Into Coarse Layers in Foundation Soil

Into Joints, Openings, Etc. in Foundation Rock


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Teton Dam, Idaho

Constructed: 1975

Failed: June 5, 1976

Seepage Failure –

During first filling11 Fatalit ies


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Quail Creek Dike

Constructed: 1984

First Filling: 1985

Failed: January 1, 1989

Seepage Failure –During first fill ing

No Fatalit ies


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Potential

Failure Mode

• Seepage carries

earthfi ll into

foundation

• Filter protects against

earthfil l being carried

by seepage into

foundation soil

• Foundation treatment

seals openings in rock

– no seepage into rock

Into Coarse Layers in Foundation Soil

Into Joints, Openings, Etc. in Foundation Rock

Filter

Protection

Foundation Treatment

(slush grouting, dental

concrete, etc.)


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Potential

Failure Mode

• Seepage along

conduits through dam

embankment

• Erodes earthfil l• Carries earthfill

downstream

• Breaches dam


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Filter material

needs to becompletely wrapped

around the conduit –

stops development

of the failure mode


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Lawn Lake Dam

Colorado

Constructed: 1903

Failed: July 15, 1982Seepage

3 Fatalities

Isabel Myron Dam


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Isabel Myron Dam

Colorado

Constructed: Unknown

Failed: 1978

Wind Tree Toppling

Overtopping (?)or Seepage (?)

0 Fatalit ies (believed)

Sl I t bili t


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Slope Instabili ty


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Potential

Failure Mode

Embankment

Dams

Dam overtopping in a flood• The capacity of the spillway(s) is

exceeded by flood flows

• Water flows over the dam crest• The overtopping flow erodes the

dam embankment

• Dam breaches

Auxi liary

spillway


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Erosion Begins

Dam is Breached

Rainbow Dam

Michigan

Failed: 1986

Flood - Overtopping


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Ka Loko Dam

Hawaii

Constructed: 1890Failed: March 14, 2006

Flood – Overtopping

7 Fatalities

B il

http://upload.wikimedia.org/wikipedia/commons/d/d2/Kaloko_breach.jpg


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Brazil

Failed: 1980’s

Flood – Overtopping

Spillway gates not opened


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Noppikoski Dam, Sweden

Constructed: Not known

Failed: September 6, 1985

Flood – Overtopping – Could not

remove stoplogs in t ime

0 Fatalities


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Spillway

failure in

a flood

event

El Guapo Dam

Venezuela



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Embankment Dams – Earthquake-Related Failure

Earthquake causes strength loss in

foundation soil leads to instability

and failure by dam overtopping

Potential

Failure Mode

Foundation so il that is saturated

and loose (not very dense)

Earthquake shaking causes

it to lose strength (liquefy)

The liquefied soil i s

more like a fluid –

has litt le shear

strength

The dam slides in the

downstream direction on

the weak layer


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Earthquake causes strength loss in

foundation soil leads to instability

and failure by dam overtopping

Potential

Failure Mode

Dam failure occurs

almost immediately after

the earthquake

Embankment Dams – Earthquake-Related Failure


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Sheffield Dam

California

Constructed: 1917

Failed: June 29, 1925

Earthquake – Liquefaction

No Fatali ties


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Lower San Fernando

(Van Norman) Dam

Los Angeles, California

Constructed: 1912, Raised 1921Nearly Failed: February 9, 1971

Earthquake

No Fatalities


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Potential

Failure Mode

Earthquake-caused cracks and/or

damage that leads to seepage-

related dam failure


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Major Types of Dams

• Embankment• Rockfill

– Central Core

– Impervious Upstream Face

• Concrete

– Gravity

– Arch

– Buttress• Masonry

• Composite

• Mostly rock, rather

than soil

• Thin impervious core

• Potential failure

modes and monitoring

are similar to

embankment dams

• Filter protection for

the core is key

Rock Rock

Impervious

Earthfill

Core

Filtering

Transition

Zones


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Rockfill Dam

Impervious

Upstream

Face

Rock

Should be free draining

Could be:

Geomembrane

Concrete

Asphalt

Steel

Clay


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Settlement of rockfill and/or earthquake shaking

could cause damage to the upstream face and

leakage

– If the rockfil l is free-draining (as it should be), this

would not be an issue (except for the lost water)

– If the rockfil l is not free-draining, then water

pressure buildup could cause slope instabili ty and

dam failure

Rock

Could be:

Geomembrane

Concrete

Asphalt

Steel

Clay Should be free draining

Rockfill Dam

Impervious

Upstream

Face


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Rock

Could be:

Geomembrane

Concrete

Asphalt

Steel

Clay Should be free draining

Rockfill Dam

Impervious

Upstream

Face

• Overtopping flow in a flood could result in

erosion at the downstream slope and toe area

• Competent rockfi ll and foundation materialshould not suffer much damage, but significant

erosion could occur in poorer materials

• Erosion Oversteepened slope Slope

Failure

Taum Sauk Dam Missouri


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Taum Sauk Dam, Missouri

Constructed: 1962


Overtopping – operational

issues

0 Fatalities


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Key Issue for all Concrete Dam Types:

Foundation Support of Structure

• Loads on the dam ultimately are transferred and carried

by the foundation (and abutments for arch dams)

• Problems with foundation support have been the cause

of the majority of concrete dam failures

Bayless (Austin) Dam


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Bayless (Austin) Dam

Pennsylvania

Constructed: 1909

Failed: September 30, 1911

Failed by Sliding in Flood

78 Fatali ties


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St. Francis Dam

CaliforniaConstructed: 1926

Failed: March 12, 1928

Sliding of Abutment

in First Filling

~450 Fatali ties


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St. Francis Dam

CaliforniaConstructed: 1926

Failed: March 12, 1928

Sliding of Abutment

in First Filling

~450 Fatali ties


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By: J. David Rogers, Professor of

Geological Engineering, MissouriUniversity of Science and Technology


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Malpasset Dam

France

Constructed: 1959


Abutment Movementin First Filling

421 Fatali ties


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Camara Dam

Brazil

Constructed: 2002Failed: June 2004

Foundation Movement

in Essentially First Filling

5-25 Fatali ties

Gibson Dam Montana 1964 dam overtopping


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Overtopping flow could erode foundation material



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Overtopping protection

provided after the event

To protect againsta future possibly

larger f lood event


Overtopping flow could erode foundation material

Cascade Dam


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Cascade Dam

Colorado


Overtopping due to failure of

upstream Lawn Lake Dam

2 Fatalities

Lawn Lake Dam

Colorado

Constructed: 1903


Seepage

3 Fatalities

Most potential


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Masonry

Dams

failure modes

similar to

concrete gravity

dams

Good foundation

support is

crucial

Castlewood Dam, ColoradoConstructed: 1890


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Constructed: 1890

Failed: August 3, 1933

Failed in Flood – Erosion at toe of dam

7 Fatalities

Leakage

May, 1990


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Delhi Dam, Iowa

Constructed: 1929


Flood – Overtopping, but failed due to seepage

0 Fatalities

Virginia Kendall Dam, Ohio

Constructed: 1930’s

Overtopped: July 21, 2003

Did not fail

Frozen Lake Dam


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Washington

Constructed: 1930

Failed: Hopefully Never

A. Embankment Dam

Seepage Failure

B. Embankment Dam

Seepage Failure


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C. Embankment Dam

Overtopping in Flood

F. Embankment Dam

E th k

E. Embankment DamEarthquake

Delayed

Failure

D. Concrete Dam

All Failure Types

Seepage Failure

Unconstrained

Development

Seepage Failure

Constrained

Development

Sudden Failure?(Limited Warning Time)

Sudden Failure

Sudden

Failure

Sudden

Failure

Not Sudden

F il

Not Sudden Failure

Large Dam

Failure Flood?

Very Large Flow

Large Flow

Large FlowLarge Flow

Maybe

No Water

Released

Maybe NoWater Released

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