Performance of Three Innovative Levee Strengthening ...

Managed by UT-Battelle for the U.S. Department of Energy – Supporting the Department of Homeland Security

Performance of Three Innovative

Levee Strengthening Systems under

Full-Scale Overtopping Testing and

Design Guidelines

Farshad Amini, Ph.D., P.E., F. ASCE

Professor & Chair

Department of Civil & Environmental Engineering

Jackson State University

October 23, 2014

Congressional Delegation Visit

http://web.mst.edu/~rogersda/levees/Marchland Levee failure Donaldsonville-LA-Aug23-1983.jpg

http://web.mst.edu/~rogersda/levees/Marchland Levee failure Donaldsonville-LA-Aug23-1983.jpg


Problems Addressed

• Levees are subjected to overtopping, causing

significant damage. Prevention methods

against overtopping must be developed.

• This project addresses innovative methods to

strengthen the crest and landside slope from

erosive forces of overtopping flows.

LeveeCombined Wave and Storm Surge Overtopping

Landside

slope

Crest


Research Objectives

• To determine the effectiveness of three

innovative levee strengthening systems

during full-scale overtopping conditions

simulating waves or combined wave and

storm surge.

– High performance turf reinforcement mat

– Articulated concrete block system

– Roller compacted concrete


Capabilities

• JSU is the leader in the area of Levee

Overtopping with more than 40

publications, many in top engineering

journals.

• Received 1.45 M from DHS for research

• Full Scale Testing

• Numerical Modeling

• Slope Stability Analysis


High Performance Turf

Reinforcement Mats (HPTRM)

• The HPTRMs have extremely

high tensile strengths, and

use a unique matrix of

polypropylene yarns and fiber

technology specially created

to lock soil in place.

HPTRM


Articulated Concrete Block

System (ACB)

• An ACB system is a matrix of machine compressed individual concrete blocks assembled to form a large mat.

• Blocks are 10 to 23 cm thick and 929 to 1858 cm2

in plan with openings penetrating the entire block.


Roller Compacted Concrete

• RCC is formed by mixture of controlled-gradation aggregate, Portland cement, mixed with water and then compacted by a roller.


Full Scale Testing at OSU

• Full-scale overtopping test bed in 104-m wave flume

• Unsteady flow consisting of wave and/or combined wave and surge.

Land-side slope

Land-side slope

Land-side slope

Land-side slope

Rc (negative)

SWL

SWL

SWL

SWL

Rc

Rc (negative)

Hs Hs

Hs

(a) Surge-only overflow (Rc < 0) (b) Wave-only overtopping (Rc > 0)

(c) Wave-only overtopping (Rc = 0) (d) Combined wave and surge overtopping (Rc < 0)

1m

1m

1m

1m

w


Levee Embankment Section

13.87 m

Crest

1

3

Water-side slope Land-side slope

3.25 m

9.75 m2.57 m

14.25

2.57 m 9.75 m

3.25 m

Vegetated HPTRM

Metal Tray

Metal Tray

CrestLandside-

slope


1. Bermuda Seed Apply

2. After 3 wks

3. After 10 wks – 7”

4. Heat & Light Enhanced

Vegetated HPTRM Setup and Maintenance


Levee Embankment in Large Wave Flume at OSU

• Physical model was set up at full scale (1:1)

• LWF is 104 m (L) x 3.66 m (W) x 4.57 m (H) with a unidirectional piston

wave maker for up to 1.6 m wave height.

4.57 mWave

maker

9.75 m13.87 m 2.57 m

311

4.25

3.25

m

Wave and surge

overtopping

Water-side

slope3.66 m

Side View

44.3 m

Wave

maker2.33 m

Cre

st Land-side

slope

Top View

17 m

9.75 m13.87 m 2.57 m44.3 m 17 m


Setup of Hydraulic Instrumentation

Surface-piercing wire wave gage

4.57

m

Wave

maker

44.3 m

Acoustic range finder

Land-side slope

0.9 m1.2 m

1.2 m

2.4 m

5.4 m

Normal ADVSide ADV

Acoustic range finder

5 wave gages,

6 acoustic range

finders,

8 ADV

Sampling at 50 Hz


Hydraulic Tests at RCC Test Section

Nine Surge-Only Overtopping Tests

Six Wave-Only Overtopping Tests

Seven Combined Wave and Surge Overtopping Tests

Combined overtopping

(Hm0 = 0.7 m, Tp = 7 s, Rc = -0.24 m


Hydraulic Tests at ACB Test Section

One Surge-Only Overtopping Test

Three Wave-Only Overtopping Tests

Four Combined Wave and Surge Overtopping Tests


(Hm0 = 0.6 m, Tp = 5 s, Rc = -0.27 m

Laser beam


HPTRM Metal Tray Installation

1. Flat-bed Truck Delivered

3. Installed in LWF

4. Light & Heat Controlled

2. Crane Lift


Hydraulic Tests at HPTRM Test Section

One Surge-Only Overtopping Test

Three Wave-Only Overtopping Tests

Five Combined Wave and Surge Overtopping Tests


(Hm0 = 0.85 m, Tp = 5 s, Rc = -0.26 m


440 445 450 455 460 465 470 475 4800

0.5

1

1.5

t, s

qw

s,

m3/s

/m

440 445 450 455 460 465 470 475 4800

0.1

0.2

0.3

0.4

0.5

t, s

flow

thic

kness,

m

440 445 450 455 460 465 470 475 480-0.2

-0.1

0

0.1

0.2

t, s

wate

r surf

ace,

m

Combined wave and

surge overtopping Trial1

of RCC tests

(measured flow thickness at crest)

(measured water surface)

(calculated avg. overtopping discharge)

(Rc = -0.29 m, Hm0 = 0.41 m, Tp = 3.4 s)

Hydraulic Data

Analysis


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0

qw

s/(

gH

m03)1

/2

Rc/Hm0

RCC

ACB

HPTRM

Europe manual (2007)

Reeve et al. (2008)

Dimensionless Average Wave/Surge

Overtopping Discharge vs. Relative Freeboard

Results

0 R 53.0034.0

58.1

03

0

c

m

c

m

ws forH

R

gH

q

Peak wave period (Tp) had negligible influence on the determination of qws

(Hughes and Nadal 2009)


-1 -0.8 -0.6 -0.4 -0.2 010

-1

100

101

102

Rc/H

m0

qw

s/q

s

RCC

ACB

HPTRM

Best fit qws

/qs=36.12exp(19.59R

c/H

m0)+1

When Rc < -0.3 Hm0, qws qs (surge-dominated cases)

When Rc > -0.3 Hm0, qws > qs (wave-dominated cases)

Relative Average Wave/Surge Overtopping

Discharge to Surge-Only Discharge vs.

Relative Freeboard

qws = qs

At higher freeboard, discharge equivalence

At lower freeboard, wave overtopping is more influential


0

0.1

0.2

0.3

0.4

0.000 0.100 0.200 0.300 0.400

Average discharge - qw s , m3/s/m

Ave

rag

e d

isch

arg

e fro

m W

eib

ull -

q w

s ,

m3/s

/m

RCC

ACB

HPTRM

Distribution of Individual Wave/Surge

Overtopping Discharge

Best fit Weibull cumulative

Probability

distribution

b

c

qqqP *

* exp1)(


0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02 0.022

Overtopping parameter - qws/(gHm0Tp)

Weib

ull

shape f

acto

r -

b

RCC

ACB

HPTRM

Best fit RCC

Best fit ACB

Best fit HPTRM

RCC ACB HPTRM

0.43

0

6.93( )ws

m p

qb

gH T 0.41

0

6.90( )ws

m p

qb

gH T 0.42

0

8.30( )ws

m p

qb

gH T

Best-fit equation for Weibull shape

factor b for all the tests


0 0.5 1 1.5 2 2.50

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

qws

Tp

We

ibu

ll S

ca

le p

ara

me

ter

- c v

Surge-dominated cases

Wave-dominated cases

Best fit curve

Distribution of Individual Wave Volume for

Combined Wave and Surge Overtopping

Best fit Weibull cumulative

Probability

distribution

Vb

Vc

VVVP *

* exp1)(

0.79v ws pc q T

RCC test section


0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45

qs , m3/s/m

(gd

s3)1

/2 , m

2/s

RCC

ACB

HPTRM

kd=0.1732

kd=0.2365

kd=0.3076

Steady Flow Thickness on Landward-side

Slope for Surge-only Overflow


0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45

qws - m3/s/m

(gd

m3)1

/2 -

m2/s

RCC

ACB

HPTRM

RCC surge

ACB surge

HPTRM surge

Average Flow Thickness on Landward-side Slope for

Combined Wave and Surge Overtopping


Average Flow Thickness Equivalency between Surge-only

Overflow and Combined Wave and Surge Overtopping

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09

ds

dm

RCC

ACB

HPTRM

Best fit

1.174m sd d


0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

-1.0 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.0

Rc/Hm0

v ws/

v s

RCC

ACB

HPTRM

Best fit

Average Flow Velocity Equivalency between Surge-only Overflow

and Combined Wave and Surge Overtopping

0

/ 3.35exp(13.59 ) 1cws s

m

Rv v

H


0 0.1 0.2 0.3 0.4 0.50

0.1

0.2

0.3

0.4

0.5

0.6

Measured H1/100

, m

Ra

yle

igh

H1

/10

0, m

RCC

ACB

HPTRM

Distribution of

Waves on the

Landside Slope

0 0.1 0.2 0.3 0.4 0.5 0.60

0.1

0.2

0.3

0.4

0.5

0.6

Measured H1/10

, m

Ra

yle

igh

H1

/10, m

RCC

ACB

HPTRM

0 0.1 0.2 0.3 0.4 0.5 0.60

0.1

0.2

0.3

0.4

0.5

0.6

Measured H1/3

, m

Ra

yle

igh

H1

/3, m

RCC

ACB

HPTRM

Rayleigh Distribution of

characteristic wave heights


0

1

2

3

4

-1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0

Rc/Hm0

Hrm

s/(-

Rc)

RCC

ACB

HPTRM

Best fit

Estimation of Hrms on Landward-side Slope

0.662

0

0.359( )rms c

c m

H R

R H


0

1

2

3

4

5

6

7

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

(gqws)1/3, m/s

Wave fro

nt velo

city

, m

/s

RCC

ACB

HPTRM

Best fit

Wave Front Velocity on Landward-side Slope

1/3

wv =4.33( )wsgq


4ft4ft

8ftarea1

area2area3

area4

8.42ft

8ft

area5

Deep

erosion

13%

Shallow

erosion

16%

No

erosion

71%

Deep

erosion

1%

Shallow

erosion

17%

No

erosion

82%

Erosion

Results

of RCC

Test

Section

No

erosion

77%

Shallow

erosion

3%Deep

erosion

20%

Area3


Settlement or Uplift Data for ACB Tests

after 90 min combined wave

overtopping and surge overflow

with Rc = -0.18 m, Hm0 = 0.69

m and Tp = 4.94 s

after 90 min combined wave overtopping

and surge overflow with Rc = -0.21 m, Hm0 =

0.64 m and Tp = 4.85 s

after 6 hr combined wave overtopping

and surge overflow with Rc = -0.27 m,

Hm0 = 0.59 m and Tp = 4.86 s


Erosion Data of HPTRM Tests

Cre

st

Te

st-s

ec

tion

1'

2'

2'

2'

2'

2'

2'

2'

2'

2'

2'

S1

S2

S3

S4

S5

S6

S7

S8

C4

C2

C3

2'

S9 2'

S10 2'

S11 2'

S12

La

nd

sid

e s

lop

e

13

'5"

2

L1

L2

L3

L4

14

"

5"

27

"

4"

17

"

X X X X

X X X X

X X X X

X X X XX X X X

X X X X

X X X X

X X X X

X X X X

X X X X

X X X X

X X X X

X X X X

X X X X

X X X X

X X X X

Cross flume, ft

Alo

ng

flu

me

,ft

(0in

dic

ate

scre

st

ed

ge

)

0 1 2 3 4 5

-20

-15

-10

-5

0

5

Erosion

1.1

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

X X X X

X X X X

X X X X

X X X XX X X X

X X X X

X X X X

X X X X

X X X X

X X X X

X X X X

X X X X

X X X X

X X X X

X X X X

X X X X

Cross flume, ft

Alo

ng

flu

me

,ft

(0in

dic

ate

scre

st

ed

ge

)

0 1 2 3 4 5

-20

-15

-10

-5

0

5

Erosion

1.1

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

12.25 After wave test2 12.25 After combined test1

(1) Elevation measurement

(inch) (inch)


Soil erosion rate versus overtopping velocity

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0.0 0.5 1.0 1.5 2.0 2.5 3.0

vws, m/s

Soil

loss r

ate

, m

m/h

r

P1

P3

P4

P5

Crest

Test-section

0.3m

S1

S2

S3

S4

S5

S6

S7

S8

C4

C2

C3

S9

S1

0

S1

1

S1

2

Landward-side slope

P1 P2 P3 P4 P5

ed

ge

L1

L2

L3

L4

0.36m

Counting

Point 1Counting

Point 2

0.6m 0.6m 0.6m 0.6m 0.6m 0.6m 0.6m 0.6m 0.6m 0.6m 0.6m0.6m 0.6m 0.6m

0.13m

0.69m

0.10m

0.43m


0

2

4

6

8

10

12

14

-2 -1.5 -1 -0.5 0

vw sRc/Hm0, m/s

So

il lo

ss, m

m

1.5hr

3hr

4.5hr

6hr1.5hr

3hr 4.5hr

6hr

Estimation for Erosion of Different Time Duration

HPTRM section


Improvement of Soil Erodibility

• Soil erodibility: relationship between the erosion rate and

the shear stress at the soil-water interface.

• Measured with Erosion Function Apparatus (EFA) by

Dr. Briaud Group at Texas A & M University.


Measurement of Soil Erodibility


Soil Erodibility Improvement

From Very high/high

erodibility decrease to

Medium/low erodibility

(HPTRM system)

(clay + dormant grass)


Soil Erodibility Improvement

From Very high/high

erodibility decrease to

Medium erodibility

(clay + dormant grass)

(HPTRM system)


Design Parameters for Three Levee

Strengthening Systems

• Under combined wave and surge overtopping, strengthening levees in crest and landward-side slopes with:– HPTRM can withstand wave overtopping of 0.2 m3/s-

m, where Dutch guideline is 0.01 m3/s-m for good quality grass cover (TAW 1989).

– RCC can withstand wave overtopping of 0.34 m3/s-m, where Goda (1985) suggested 0.05 m3/s-m for concrete protected side slopes.

– ACB can withstand wave overtopping of 0.17 m3/s-m


Empirical Equations for Three Levee

Strengthening Systems Design under Surge-

only Overflow Conditions

Design parameters Empirical equations developed by this study

steady overflow d ischarge q s 3/ 2

1s fq C gh where Cf is 0.5445 for RCC, 0.4438 for ACB, and

0.415for HPTRM strengthened levees.

average flow thickness d s on

landward -side slope

3

s

d

s

gdk

q , where kd is 0.1732 for RCC, 0.2365 for ACB, and 0.3076

for HPTRM strengthened levees.

steady flow velocity v s on

landward -side slope 1s vv k gh , where kv is 2.628 for RCC, 1.995 for ACB and 1.637 for

HPTRM strengthened levees.



Strengthening Systems Design under Combined

Wave and Surge Overtopping ConditionsDesign parameters Empirical equations developed by this study

dimensionless average

wave overtopping

d ischarge qws/ qs 0

/ 36.12exp(19.59 ) 1cws s

m

Rq q

H

distributions of

instantaneous

overtopping d ischarge

**( ) 1 exp[( ) ]bq

P q qc

, where c can be calculated by , b

can be calculated by where is 6.93 for RCC, 6.9 for

ACB and 8.3 for HPTRM strengthened levees, and Γ is the gamma

function.

average flow thickness

d m on landward -side

slope

1.174m sd d

average flow velocity vws

on landward -side slope 0

/ 3.35exp(13.59 ) 1cws s

m

Rv v

H

Distribution of wave

heights on landward -

side slope

1/3 1.416 rmsH H , 1/10 1.80 rmsH H , 1/100 2.36 rmsH H



Strengthening Systems Design under Combined

Wave and Surge Overtopping ConditionsDesign parameters Empirical equations developed by this study

Wave front velocity vw

on landward -side slope

1/3

wv =4.33( )wsgq

Root-mean-square of

shear stress t,rms on

landward -side slope

, 0.0547t rms w mh for HPTRM strengthened levee

Distribution of shear

stress on landward -side

slope

t,1/3 t,rms0.976 , t,1/10 t,rms2.36 ,

t,1/100 t,rms7.04 for HPTRM

strengthened levee

Maximum soil loss

depth Emax, in mm max 11.23 16.24wsE v for HPTRM strengthened levee, where vws is

the average overtopping flow velocity in m/ s

Erosion rate E in mm/ hr 5.3 9.3wsE v for HPTRM strengthened levee

Erosion rate E in mm/ hr 4.44

0

0.394+0.735( )cws

m

RE v

H


Summary & Conclusions• Effectiveness of HPTRM, RCC, and ACB were

investigated with full-scale overtopping tests.

• HPTRM, RCC, and ACB can significantly decrease the flow velocity on landward-side slope.

• Average overtopping discharges are HPTRM < ACB <

RCC for the same hydraulic conditions.

– For Rc/Hm0 < -0.3, qws/qs is close to 1.

– For -0.3 < Rc/Hm0 < 0, qws/qs increases sharply with -Rc/Hm0

• Average flow thicknesses on landward-side slope are

RCC < ACB < HPTRM for the same overtopping

discharge

– dm/ds = 1.174


Summary & Conclusions• Average flow velocities are HPTRM < ACB < RCC for the same

overtopping discharge

– For Rc/Hm0 < -0.3, vws/vs is close to 1.

– For -0.3 < Rc/Hm0 < 0, vws/vs increases sharply with -Rc/Hm0

• Wave front velocities are HPTRM < ACB < RCC for the same

relative freeboard.

• HPTRM system has the best effect in reducing overtopping

discharge and wave front velocity on landward-side slope, while

RCC has the least effect.

• Flow equivalency shows that the impact of wave on overtopping

parameters weakens with an increase in the negative relative

freeboard.

• The maximum erosion depth in HPTRM test section is mainly

impacted by overtopping flow velocity.


Summary & Conclusions• After the maximum soil loss is reached, the relationship between

erosion rate and average overtopping flow velocity is approximately

linear.

• Both the grass roots and HPTRM can increase the critical velocity

by 1 m/s. The erodibility of the soil is lowered from high erodibility to

median erodibility by both the grass roots and HPTRM.

• HPTRM can strengthen the clay levee by increasing the threshold

value of both flow velocity and shear stress.

• Aside from the surface erosion, the RCC remained intact throughout

all of the experimental tests, and there was no catastrophic failure in

the RCC test section.

• According to this full-scale overtopping test, the crest and landward-

side slope strengthened by HPTRM, RCC and ACB can withstand

wave overtopping of 0.2, 0.34, and 0.17 m3/s/m, respectively in the

combined wave and surge overtopping conditions.


THE END

Performance of Three Innovative Levee Strengthening ...

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