PREDICTION OF BRIDGE SCOUR DEPTH AND LEVEE OVERTOPPING EROSION · 2010-08-26 1 PREDICTION OF BRIDGE SCOUR DEPTH AND LEVEE OVERTOPPING EROSION Jean-Louis Briaud President of ISSMGE

2010-08-26

1

PREDICTION OF BRIDGE SCOUR DEPTH

AND LEVEE OVERTOPPING EROSION

Jean-Louis Briaud

President of ISSMGE

Professor at Texas A&M University

Seung Jae Oh, Michelle Bernhardt

PhD Students, Texas A&M University

• Fundamentals

• Scour depth

predictions for bridges

• Overtopping erosion of

levees

2010-08-26

2

Erosion process

2010-08-26

3

Erosion process

RANS Equations Continuity equation

Momentum (RANS) Equations

Energy Equation

0)U(t

m,

m

m,

i

n,

mn

m,

imimmnmi

mn

nm

lmn

ilim

m,

i

m,

mi

Ugpgg

Ueg2RUUt

U

uuUUgguuUU

Dt

DpKTgTuTU

t

TC

j

n

i

m

j

n

i

m

mn

ij

n

m

m

n

n

m

m

n

mn

mn

m

m

m

m

p

,,,,,,,,

,,,,

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4

Reynolds Stresses Transport Equations

• Production

• Diffusion by um

• Diffusion by p

• Viscous Diffusion

• Pressure-Strain

• Dissipation

ijijij

v

ij

p

ij

u

ijij

m,

mij

DDDPRUt

R

j

n,

i

m,

mnij

i

m,

jmj

m,

imij

ij

mn,

mnij

v

m,

jim

m,

ijmij

p

m,

jimij

u

injljnilm

lmn

i

m,

jmj

m,

imij

uug2

)ugug)(/'p(

RgD

)/ρ'pu(g)/ρ'pu(gD

)uuu(D

)RgRg(e2

)URUR(P

Two-Layer k- ModelOuter Layer (Fully Turbulent Region)

2b31

m,

n,tmn

m,

m

b

m,

n,

k

tmn

m,

m

CPCPCk

gUt

PPkgkUt

k

Inner Layer (Near-Wall Region)

AR1yC ;AR1yC

kC ;k

PPkgkUt

k

yy

t

3/2

b

m

n

k

tmn

m

m

/exp/exp

,

,,

Compute wall shear stress directly without wall function approximation

2010-08-26

5

222

b

cb

cbcb

cb

WVUq n

q

0

cZ

ZZ

;

,

,

),(

Scour Rate Equation

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6

CHEN 3D

Testing for erodibility (EFA)

EFA (Erosion Function Apparatus)

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7



Erosion function for a fine sand

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Erosion function for a low PI clay

Testing for erodibility (PET)

PET (Pocket Erodometer Test)

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9

Jean-Louis BRIAUD – Texas A&M University

17NIAGARA FALLS

11000 m of lateral erosion from Lake Ontario

towards Lake Erie in 12000 years or 0.1 mm/hr

From Google Earth

http://www.iaw.com/~falls/origins.html

http://www.samizdat.qc.ca/cosmos/origines/niagara/niagara.htm

Lake Erie

Lake Ontario

Niagara River

1841

1841

2006

Niagara Falls


18

GRAND CANYON

1600 m of vertical erosion by the Colorado River

in 10 Million years or 0.00002 mm/hr

2010-08-26

10


19

If your faucet drips on a pebble for 20 million years, will there be

a hole in the pebble?


20

EFA test on

Creamy Peanut Butter

Su = 1.8 kPa

Vc = 1.4 m/s

0.1

1

10

100

1000

10000

100000

0.1 1.0 10.0 100.0

Velocity (m/s)

Very High

Erodibility

I

High

Erodibility

II

Medium

Erodibility

III

Low

Erodibility

IV

Very Low

Erodibility

V

Erosion

Rate

(mm/hr)

0.1

1

10

100

1000

10000

100000

0 1 10 100 1000 10000 100000

Shear Stress (Pa)

Very High

Erodibility

I

High

Erodibility

IIMedium

Erodibility

IIILow

Erodibility

IV

Very Low

Erodibility

V

Erosion

Rate

(mm/hr)

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11

Erosion classification (velocity)

0.1

1

10

100

1000

10000

100000

0.1 1.0 10.0 100.0

Velocity (m/s)

Very High

Erodibility

I

High

Erodibility

II

Medium

Erodibility

IIILow

Erodibility

IV

Very Low

Erodibility

V

Erosion

Rate

(mm/hr)

-Fine Sand

-Non-plastic Silt -Medium Sand

-Low Plasticity Silt -Fine Gravel

-Coarse Sand

-High Plasticity Silt

-Low Plasticity Clay

-All fissured

Clays-Cobbles

-Coarse Gravel

-High Plasticity Clay

-Riprap

- Increase in Compaction

(well graded soils)

- Increase in Density

- Increase in Water Salinity

(clay)

Non-Erosive

VI-Intact Rock

-Jointed Rock

(Spacing < 30 mm)

-Jointed Rock

(30-150 mm Spacing)

-Jointed Rock

(150-1500 mm Spacing)

-Jointed Rock

(Spacing > 1500 mm)

Erosion classification (shear stress)

0.1

1

10

100

1000

10000

100000

0 1 10 100 1000 10000 100000

Shear Stress (Pa)

Very High

Erodibility

I

High

Erodibility

II

Medium

Erodibility

III

Low

Erodibility

IV

Very Low

Erodibility

V

Erosion

Rate

(mm/hr)

-Fine Sand

-Non-plastic Silt

-Medium Sand

-Low Plasticity Silt-Fine Gravel

-Coarse Sand

-High Plasticity Silt

-Low Plasticity Clay

-All fissured

Clays-Cobbles

-Coarse Gravel

-High Plasticity Clay

-Riprap

- Increase in Compaction

(well graded soils)

- Increase in Density

- Increase in Water Salinity

(clay)

Non-Erosive

VI-Intact Rock

-Jointed Rock

(Spacing < 30 mm)

-Jointed Rock

(30-150 mm Spacing)

-Jointed Rock

(150-1500 mm Spacing)

-Jointed Rock

(Spacing > 1500 mm)

2010-08-26

12

• Fundamentals

• Scour depth



levees


24

60% of BRIDGE FAILURESARE DUE TO SCOUR

0

100

200

300

400

500

600

700

800

900

1000

Co

nstr

ucti

on

Co

ncre

te

Dete

rio

rati

on

Eart

hq

uake

Natu

ral

Ste

el

Fir

e

Mis

c.

Ov

erl

oa

d

Co

llis

ion

Hy

dra

uli

c

Cause

Nu

mb

er

of

Failu

res f

rom

1966 t

o 2

005 (

1502 T

ota

l)

0%

10%

20%

30%

40%

50%

60%

Perc

en

t

2010-08-26

13

Austin 2010-3-19

Observed failure modes of bridge due to scour

(based on failure photos in Briaud’s files)

25

Case 1 - Big Scour Hole

26% Observed Occurrence Case 2 – Settlement of Pier

32% Observed Occurrence

Case 3 - Loss of Deck


Case 4 - Loss of Pier


Courtesy of the University of Kentucky at Louisville

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Hatchie River Bridge, Tennessee

2010-08-26

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2010-08-26

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2010-08-26

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Austin 2010-3-19

Tie the two decks

with cables

40

Increase the support

length

2010-08-26

21

Scour types

Normal Water Level

Probable Flood Level

y s(Abut) Applies

is Abutment Scour Depth

is Contraction Scour Depth

is Pier Scour Depth

Where,

y s(Abut)

y s(pier)

y s(Cont) Applies

y s(Cont)

y s(Abut)

y s(Cont)

y s(pier)

CL

J.-L. Briaud, Texas A&M University

FOUNDATION DESIGN

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2010-08-26

26


Maximum pier scour (Oh, 2009)

where,

0.7( )

1 ( ) ( )2.2 2.6'

s Pier

w spL pier c pier

yK K K K Fr Fr

a

0.33

1 10.89 , for 1.43' '

1.0 , else

w

y y

K a a

1

1.0 , for 30

Value in following Table , elseK

1.0, for whole range of /LK L a

0.91

2.9 , for 3.42' '

1.0 , else

sp

S S

K a a

Shape of pier nose Shape of pier nose

Square nose 1.1 Circular cylinder 1.0

Round nose 1.0 Sharp nose 0.9

1K1K

2010-08-26

27

Maximum pier scour (Oh, 2009)

y = 1.0003x + 0.0013R² = 0.8031

0

1

2

3

4

5

6

0 1 2 3 4 5 6

ys(pier)/a

2.2(2.6Fr(pier)-Frc(pier))0.7

y/a= 16 y/a = 6.4 y/a = 6.6 y/a=5.33 y/a = 3.4

y/a = 2.13 y/a = 2.0 y/a = 1.67 y/a = 1.43

Maximum and uniform contraction scour

2010-08-26

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Jean-Louis Briaud – Texas A&M University


B2/B1 = 0.75

2010-08-26

29


B2/B1 = 0.5


B2/B1 = 0.25

2010-08-26

30

y = 0.9985x - 0.0011R² = 0.9502

0

0.5

1

1.5

2

2.5

0 0.5 1 1.5 2 2.5

ys(Cont)/y

m1

Li (Long contraction) (2002)

WW in rect.

Best Fit

21.27 1.83 m mcFr Fr

Maximum and uniform contraction scour (Oh, 2009)

( )

2

1

1.27 1.83s Cont

m mc

m

yFr Fr

y

Maximum abutment scour (Briaud et al. 2009)

2010-08-26

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32



y = 1.000xR² = 0.972

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 1 2 3 4 5

ys

(ab

ut)

/ y

f1

27.94 1.65 f fcFr Fr

( )

1 2 Re 2

1

7.94 1.65s Abut

L G f fc

f

yK K K K K Fr Fr

y

2010-08-26

33

0

10

20

30

40

50

60

0 50 100 150 200 250

Time(hr)

Sco

ur

Dep

th (

mm

)

Measurement

Hyperbola

iZ

Zmax

Hyperbola Model:

max

( )1

i

tz t

t

z z

Scour Depth versus Time

Jean-Louis Briaud-Texas A&M University

X/B

Y/B

-1.5 -1 -0.5 0 0.5 1 1.50

0.25

0.5

0.75

1

1.25

1.5

max

Re

104

105

106

1070.005

0.01

0.015

0.02

0.025

0.03

max =f(Re)

ma

x

U2

U

2

WEI (1997)


1

2

max( )

1 10.094

log Re 10Pier V

2010-08-26

34

Time dependent predictions

0

200

400

600

800

1000

0 10 20 30 40

(mm/hr)

z

(Pa)

3.9 Pac

max

iz


2010-08-26

35

Flood 1

V1

Flood 2

V2

t1 t2

V

Multi-flood System

Equivalent time te:

The time required for a flood

in the hydrograph to create

the same scour depth as the

one created by all previous

floods in the hydrograph.

Small flood followed

by big flood


Layer 1

Layer 2

Z1

Multi-layer System

Equivalent time te:

The time required for a flood

in the hydrograph to create

the same scour depth as the

one created by all previous

floods in the hydrograph.

V

Z2

Hard soil layer over

soft soil layer


2010-08-26

36

kR=contraction ratio factor

ka=transition angle factor

kWa=contraction length factor

kw=water depth factor (=1)

* kR, k, kL,kw are the correction factors for max

SRICOS-EFA Method

Pier Scour Contraction Scour

General Information

(Units, Analysis period)

General Information


General Information


GeometryPier Parameters: Dimensions, Spacing, Attack angle, etc.

GeometryAbutment Parameters: Dimensions, Shape, water depth,

channel configuration,etc.

GeometryChannel Information: Channel widths, Lengths,

Transition angle, etc.

WaterHydraulic Information: Hydro grapth, Manning value,

River hydraulic radius, Velocity, Water depth, etc.

1.5

1.0 0.990

a

2

0.77 1.36 1.98' '

a aW W

L L

( )

2( )

1

2.21 1.31s Cont

Cont mc

m

yFr Fr

y

1

2 2 3max( ) 1Cont R Wa w hk k k k n V Ra

2 0.45

max( ) 112.45 ReAbut Cr sh Fr s sk L ok k k k k k k V

* max Calculation Factors

kCr=conveyance ratio factor

ksh=aspect ratio factor

kFr=Froude number factor

ks=shape factor

ksk=skew angle factor(=1)

kL=abutment location factor

ko=overtoppting factor

* ys(Abut) Calculation Factors

K1=shape factor

K2=skew angle factor

KL=abutment location factor

Kp=pressure flow factor = ko

' '

1 1

0.37 1.55 , <1.5

1.0 , otherwise

f f

f f

L L L L

y y

1.22 for VW

1.0 for WW

0.73 for ST

2

1

3.65 2.91q

q

0.24'

0.85a

L

W

2.07 0.8 Fr>0.1

1.0 Fr 0.1

Fr

1.0 for VW

0.65 for WW and ST

Result

Abutment Scour

Result

1

2

max( )

1 10.094

log Re 10pier w sh spk k k k Va

Note:a: width of pier a’ : projected pier width a: contraction transition angle d1: distance from water surface to low chord of bridge deck Fr: Froude number (based on V1 and yf1)

Fr(pier): Froude number (based on V1 and a’’) Frc(pier): Froude number (based on Vc and a’’) Fr2(Cont): Froude number (based on V2 and ym1) Frmc: Froude number (based on Vmc

and ym1) Fr2(Abut): Froude number (based on Vf2 and yf1) Frfc: Froude number (based on Vfc and yf1) h: distance from low chord of bridge deck to toe of abutment

L: length of pier L’: length of abutment projected to normal to flow Lf: width of floodplain n: Manning’s coefficient : Attack angle q1: approach unit

discharge q2: unit discharge around the abutment : unit mass of water at 20C Rh: Hydraulic radius Re: Reynolds number (based on a or Wa) S: spacing of group pier

V1: approach average velocity Wa: width of bridge crest or length of channel contraction yf1: floodplain water depth before contractionfor open channel or h for pressure flow

ym1: main channel water depth before contraction ys(Pier): maximum pier scour depth ys(Cont): maximum contraction scour depth ys(Abut): maximum

abutment scour depth

0.7( )

1 ( ) ( )2.2 2.6'

s Pier

sp L w pier c pier

yK K K K Fr Fr

a

max Calculation Factors

ksh = shape factor

k = attack angle factor

kw = water depth fractor

ksp = spacing factor

* ys(Pier) Calculation Factors

K1 = shape factor

Kw = water depth factor

Ksp = spacing factor

KL = aspect ratio in rectangular pier (=1)

4

1.15 7L

ae

0.57

1 1.590

1.1

1 5S

ae

4

1 16y

ae

1.1 for rectangular nose

1.0 for round nose & cylinder

0.35

1 10.89 , for < 1.43' '

1.0 , for otherwise

y y

a a

0.91

2.9 , for < 3.2' '

1.0 , for otherwise

S S

a a

WaterHydraulic Information: Hydro graph, Manning’s n,

Velocity, Water depth, etc.

SoilInput EFA Curve

SoilInput EFA Curve

Result

WaterHydraulic Information: Hydro grapth, Manning value,

River hydraulic radius, Velocity, Water depth, etc.

SoilInput EFA Curve

1.75

2

1

0.62 0.38q

q

1 1

2

1 1 1

1

2.75 / 1, / 0.33

1.83 / 3.76 / 2.97, 0.33 / 1.0

1.0, 1.0 /

d h if d h

d h d h if d h

if d h

'

' '

' '

'

1.0 / 2

0.6( ) / 1.2 2 ( ) / 0

1.2( ) / 1.2 0 ( ) / 1

1.0 1 ( ) /

f f

f f f f

f f f f

f f

L L y

L L y L L y

L L y L L y

L L y

1.0 0.005 90 60 120

0.85

for

otherwise

( ) 0.28

1 2 2 2

1

243 Re 1.65s Abut

L G p f f fc

f

yK K K K K Fr Fr

y

http://ceprofs.tamu.edu/briaud/

Woodrow Wilson Bridge Hydrography

0

2000

4000

6000

8000

10000

12000

1960 1963 1966 1970 1973 1976 1979 1983 1986 1989 1992 1995 1999

Time (year)

Disc

harg

e (m

3 /sec)

Scour Depth Vs Time

0

1000

2000

3000

4000

5000

6000

7000

1960 1965 1970 1975 1980 1985 1990 1995

Time (year)

Scou

r Dep

th (m

m)



2010-08-26

37

Hydrograph (Add 500year flood)

0

3000

6000

9000

12000

15000

18000

1960 1970 1980 1990 2000

Time (Year)

Strea

mflo

w (m

3 /s)

Scour Depth Vs. Time (Add 500year flood)

0

2

4

6

8

10

12

1960 1970 1980 1990 2000

Time (Year)

Scou

r Dep

th (m

)


Q100 – Q500 APPROACH

d’

P(d’)

ds

P[d’>ds]

2010-08-26

38

0

2000

4000

6000

8000

10000

12000

1960 1970 1980 1990 2000S

trea

m f

low

(m

3/s

)

Time (Year)

0

1

2

3

4

5

6

7

8

9

1960 1970 1980 1990 2000

Scou

r Dep

th (m

)

Time (Year)

Flow vs. Time

Pier scour depth vs.

Time

What is the frequency of occurrence and probability of

exceedance for Q100 = 12,629 m3/s, Q500 = 16,639 m3/s , and Lt =

75 yrs?

Frequency of

Occurrence vs. Scour

Depth

Probability of

exceedance vs. Scour

Depth

2010-08-26

39


77

New

Woodrow Wilson

Bridge


78

2010-08-26

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79

Bascule Pier Layout (M1)

Direction

of Flow

Pedestal

Arch Rib

39

.2 m

26.5 m

1.8 m Dia.

open ended

steel pipe pile

EL. 4 m (500 yr)

EL. 3 m (100 yr)

EL. 0.6 m (Ave.)

EL. -10.5 m (River Bottom)

Estimated Tip EL. -68.6 m

58.1

m5

.9 m

0

2000

4000

6000

8000

10000

12000

1960 1970 1980 1990 2000

Str

eam

flo

w (

m3/s

)

Time (Year)

0

1

2

3

4

5

6

7

8

9

1960 1970 1980 1990 2000

Scou

r Dep

th (m

)

Time (Year)

Flow vs. Time

Pier scour depth vs.

Time

2010-08-26

41


81

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

HEC-18

Sand

(Pile

Width)

HEC-18

Sand

(Pile

Cap)

Salim-

Jones

HEC-18

Clay

(Texas

A&M)

Erodibility

Index

Large

Scale

Flume

Test

Small

Scale

Flume

Test

Selected

Scour

Scour

Depth

(m

)

Comparison of Scour Predictions

Bascule Pier M1 (500yr Flood)


82

NOT TO SCALE

NEW BRIDGE WITH STRATIGRAPHY

TO SCALE

2010-08-26

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Verification

• Maximum complex pier scour equation

0

1

10

100

0.1 1 10 100

Pre

dic

tio

n (

m)

Measurement (m)

Prediction vs. Froehlich’s pier scour

database (1988)

Prediction vs. Muller and Lander’s pier

scour database (1996)

0

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4 5 6 7 8

Pre

dic

tio

n (m

)

Measurement (m)

Verification

• Uniform contraction scour

0

5

10

15

20

25

30

35

40

45

50

55

0 5 10 15 20 25 30 35 40 45 50 55

Pre

dic

ted

sco

ur

de

pth

by

Eq.(

7.7

)(m

m)

Measurement (mm)

Prediction vs. Gill’s uniform contraction scour

database (1981)

2010-08-26

43

Verification

• Maximum abutment scour I

Prediction vs. Froehlich’s abutment scour

database (1981)

Prediction vs. Sturm’s abutment scour

database (2004)

0

0.1

0.2

0.3

0.4

0.5

0 0.1 0.2 0.3 0.4 0.5

Pre

dic

tio

n (

m)

Measurement (m)

Tey VW (1984) Liu V.W. (1961) Gill V.W. (1972) Kwan V.W.(1984)

Garde V.W.(1961) Tey W.W. (1984) Wong W.W. (1982) Kwan W.W. (1984)

Liu S.T.(1961) Tey S.T. (1984) Wong S.T.(1982) 1 to 1 Line

F.S = 2.0

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.1 0.2 0.3 0.4

Pre

dic

ito

n (m

)

Measurement (m)

VW(Long) VW(Inter) VW (Short) ST(Inter) ST (Short) WW (Inter)

F.S = 2.0

Verification

• Maximum abutment scour II

Prediction vs. Ettema et al.’s abutment scour

database (2008)

Prediction vs. Benedict et al.’s abutment

scour database (2006)

0

0.1

0.2

0.3

0.4

0.5

0.6

0 0.1 0.2 0.3 0.4 0.5 0.6

Pre

dic

tio

n (

m)

Measurement (m)

ST

WW

1to1 Line0

1

2

3

4

5

6

0 1 2 3 4 5 6

Pre

dic

tio

n (

m)

Measurement (m)

Q100

Historic data

2010-08-26

44

• Fundamentals

• Scour depth



levees

Earthen Embankment Case

Overtopping Erosion

2010-08-26

45

Overtopping Erosion

(NSF, Deretsky, 2009)

Overtopping can occur during:• Hurricane Events

– Sheet-like flow from storm surge combined with effects from wave impacts

• Flood Events

– Sheet-like flow

– Heavy precipitation

– High river levels

Erosion Process

• Begins at toe

• Progresses back to crest

(USACE, 2009)

Overtopping Erosion

2010-08-26

46

Overtopping Erosion

Overtopping During Hurricane Events

Hurricane Katrina

New Orleans, Louisiana

Overtopping Erosion

THE EVENT

• 250 miles in diameter

• 25 miles per hour

• 6000 wave cycles

• Storm surge 10 hours

• Duration over a bridge or levee = 10 hours

2010-08-26

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Overtopping Erosion

Storm Surge

8.5 m

4.6 m

3.0 m

Overtopping Erosion

Storm Surge

2010-08-26

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Overtopping Erosion

Overtopping Erosion

2010-08-26

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Overtopping Erosion

Overtopping ErosionFrom Raymond B. SEED

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Overtopping Erosion

From Raymond B. SEED

Overtopping Erosion

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Overtopping Erosion

THE INVESTIGATION



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103EFA TEST RESULTS - Erosion rate vs velocity

0.1

1

10

100

1000

10000

100000

0.1 1.0 10.0 100.0Velocity (m/s)

S1-B1-(0-2ft)-TW S1-B1-(2-4ft)-SW S2-B1-(0-2ft)-TW

S2-B1-(2-4ft)-SW S3-B1-(2-4ft)-SW S3-B2-(0-2ft)-SW

S3-B3-(0-1ft)-SW S4-(0-0.5ft)-LC-SW S4-(0-0.5ft)-HC-SW

S5-(0-0.5ft)-LT-SW S6-(0-0.5ft)-LC-SW S7-B1-(0-2ft)-TW

S7-B1-(2-4ft)-SW S8-B1-(0-2ft)-TW S8-B1-(2-4ft)-L1-SW

S8-B1-(2-4ft)-L2-SW S11-(0-0.5ft)-LC-TW S11-(0-0.5ft)-HC-TW

S12-B1-(0-2ft)-TW S12-B1-(2-4ft)-SW S15-Canal Side-(0-0.5ft)-LC-SW

S15-CanalSide-(0-0.5ft)-HC-SW S15-Levee Crown-(0-0.5ft)-LT-SW S15-Levee Crown-(0.5-1.0ft)-LT-SW

Very High

Erodibility

I

High

Erodibility

II Medium

Erodibility

III

Low

Erodibility

IV

Very Low

Erodibility

V

Erosion

Rate

(mm/hr)


104EFA TEST RESULTS - Erosion rate vs shear stress

0.1

1

10

100

1000

10000

100000

0 1 10 100 1000 10000 100000Shear Stress (Pa)









Very High

Erodibility

I

High

Erodibility

II

Medium

Erodibility

III

Low

Erodibility

IV

Very Low

Erodibility

V

Erosion

Rate

(mm/hr)

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105

NUMERICAL SIMULATION


106

t = 0.80 sec

t = 1.28 sec

t = 1.60 sec

t = 1.92 sec

t = 2.39 sec

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107SHEAR STRESSES ON LEVEE SURFACE


108EFA TEST RESULTS - Erosion rate vs shear stress

0.1

1

10

100

1000

10000

100000

0 1 10 100 1000 10000 100000Shear Stress (Pa)









Very High

Erodibility

I

High

Erodibility

II

Medium

Erodibility

III

Low

Erodibility

IV

Very Low

Erodibility

V

Erosion

Rate

(mm/hr)

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109

LEVEES – FAILED and NOT FAILED

0.1

1

10

100

1000

10000

100000

0.1 1.0 10.0 100.0Velocity (m/s)

S2-B1-(0-2ft)-TW S2-B1-(2-4ft)-SW S3-B1-(2-4ft)-SW

S3-B2-(0-2ft)-SW S3-B3-(0-1ft)-SW S4-(0-0.5ft)-LC-SW

S5-(0-0.5ft)-LT-SW S6-(0-0.5ft)-LC-SW S15-Canal Side-(0-0.5ft)-LC-SW


Very High

Erodibility

I

High

Erodibility

II Medium

Erodibility

III

Low

Erodibility

IV

Very Low

Erodibility

V

Erosion

Rate

(mm/hr)

Note:

- Solid circles =

levee breaches

- Empty circles =

no levee damage

Overtopping Erosion

Levee Overtopping Chart for Hurricane Events – 2 hours

0.1

1

10

100

1000

10000

100000

0.1 1.0 10.0 100.0

Velocity (m/s)

Erosion

Rate

(mm/hr)

Very High

Erodibility

I

High

Erodibility

IIMedium

Erodibility

III

Low

Erodibility

IV

Very Low

Erodibility

V

TRANSITION

ZONE

PRONE TO

FAILURE BY

OVERTOPPING

PRONE TO

RESIST

OVERTOPPING

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Overtopping Erosion

Overtopping During

Floods Events

Midwest Levees

Summer 2008

Flow Frequency Analysis

7 year flood

1000 year flood

13 year flood

6 year flood

Overtopping Erosion

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Winfield – Pin OakOvertopping Erosion

Brevator (Did Not Fail)Overtopping Erosion

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Overtopping Erosion

Overtopping Erosion

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Overtopping Erosion

Sample Collection

Overtopping Erosion

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In-situ testing

Overtopping Erosion



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Overtopping Erosion

EFA test results – Erosion rate versus water velocity

Overtopping Erosion

LEVEES – Failed and Not Failed

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Overtopping Erosion

Levee Overtopping Chart for Flood Events – 2 days

Vegetative ArmorOvertopping Erosion

Good grass type and coverage Poor grass type and coverage

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Vegetative Armor

Recommendations:

• Mat-like, sod-forming root system

• Perennial grasses

• Dense consistent coverage

• Height above 0.3 m during flood season

• Trees limited to 15 m beyond levee toe

Overtopping Erosion

Overtopping Erosion

ELEVATED HOUSES

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Overtopping Erosion

Overtopping Erosion

ESCAPE STRUCTURES

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Briaud’s Web Site


International Conference on Scour and ErosionSan Francisco, 7-10 November 2010

www.icse-5.org

International Society for Soil Mechanics and Geotechnical Engineering

http://www.issmge.org/




http://www.icse-5.org/



http://www.issmge.org/

Documents

PREDICTION OF BRIDGE SCOUR DEPTH AND LEVEE OVERTOPPING EROSION · 2010-08-26 1 PREDICTION OF BRIDGE SCOUR DEPTH AND LEVEE OVERTOPPING EROSION Jean-Louis Briaud President of ISSMGE