ÉÉRosionRosion INterneINterne dans les dans les OuvragesHydrauliquesOuvragesHydrauliques Internal Erosion in Hydraulic WorksInternal Erosion in Hydraulic Works

EssaisEssais de de laboratoirelaboratoire (CEMAGREF)

Nadia BenahmedNadia Benahmed

PROJET ANR PGCU ERINOH

1993 Camargue dikes, France

12 breaches in December 1993 and 4 breaches in January 1994

Saint-Gilles flood, 2003

Breache of Fourques, Petit Rhône Rive Droite

The Ouches Dam, 2001 (200 years old)

- 3 total breaches- 3 partial breaches- 5 fatalities

Sinkholes

Rupture of Aramon dike, 2002

Contexte

On sait depuis quelques années qu’il y a environ 8000 km de digues de protection contre les inondations en France :

– 8700 km* au dernier recensement

– … dont 2500 km* dans les régions Provence-Alpes-Côte d’Azur (1890 km : 1/22) et Languedoc-Roussillon (650 km : 4/22)

… mais depuis peu de temps que :

– 2700 km* de digues (existantes) de classes A et B doivent faire l’objet d’une étude de dangers d’ici le 31/12/2012

– 3200 km* de classe C d’ici le 31/12/2014

* Sources : logiciel BarDigues (R Tourment, M. Wolff – Cemagref)

Rappel

Internal erosion : complex phenomenon which affect stability of hydraulic works (earth dams, dykes,…) Failure

ERINOH 2008 Four types of internal erosion:

• Regressive erosion • Contact erosion• Suffosion• Piping flow erosion

Ouches dam, july

2001

Brief

review…Sherard et al. 1976:

Pinhole Test Apparatus

Lack: Qualitative test, no quantitative data!

Other references :

Hole Erosion test (Christensen & Das, 1973)

Leakage Erosion test (Hjeldnes & Lavania, 1980)

Drill Erosion test (Lefebvre, 1986) (Canada)

Crack Erosion test (Sanchez & al., 1983; Maranha das Neves, 1987)

Surface and Internal Erosion test (Reddi, Lee & Bonala, 2000)

Constat :

Several experimental procedures

Dispersion and different interpretations of experimental results

Nonexistence of appropriate theoretical model to fit the

experimental data !!!

Brief

review…

Pressure transducersTurbidity meter

Flowmeter

Hole

Erosion Device

(CEMAGREF)

Turbidity meter

Pressure outSample

Pressure in

Flow in

Flow out

Experimental

results

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0:00:00 0:15:00 0:30:01 0:45:01 1:00:01 1:15:01 1:30:02 1:45:02 2:00:02

Temps (h)

Déb

it Q

(kg/

h) ;

Turb

idité

(NTU

)

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Gra

dien

t de

pres

sion

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ta P

(kPa

)

Turbidité (NTU)Débit massique (kg/h)Delta P (kPa)

( )sinon

si

0er b c b ckm

τ τ τ τ⎧ − >⎪= ⎨⎪⎩

&

Loi d’érosion à seuil : Paramètres d’érosion :

• Seuil d’érosion τc• Coefficient d’érosion kd

• Seuil d’érosion τc• Coefficient d’érosion kd

0

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71 10 100 1000

Eros

ion

rate

inde

x Ie

Fell DataSample N°1

Critical shear stress τc (Pa)

Moderatly rapid

Very rapid

Moderatly slow

Very slow

Extremely slow

Extremely rapid

Wan and Fell guidelines

Experimental

results

Wan and Fell (2002, 2004)

Experimental

resultsSlot erosion test :

Sample before erosion Sample during testing Sample after erosion

Hole erosion test :

Sample after erosionSample before erosion Sample after erosion

Sample before erosion Sample after erosion, upstream side

Naturel soil : Silty sand (26% sand, 58% silts, 16% clay)

Sample after erosion, down stream side

Naturel soil : Sandy silt (72% sand, 23% silts, 4% clay)

Collapse of the sample during filling of the testing cell

Experimental

results

Soil : KAOLINITE

0.001 0.01 0.1 1 10 100Dimension des particules (mm)

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Tam

isat

(%)

KAOLIN

pH 4 to 9

Density : 2.6 g/cm3

Dry density Opt. : 1.51 t/m3

W Opt. : 23.5 %

Wl = 49 Wp = 33 Ip = 16 Grain size distribution

Experimental

study

Effect of moisture content on τc and Ie (ρd = 1.4 t/m3 (95% OPN))

0

10

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16 20 24 28 32

Moisture content W (%)

Crit

ical

she

ar s

tress

τc

(Pa)

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16 20 24 28 32

Moisture content W (%)

Eros

ion

rate

inde

x Ie

Effect of dry density on τc and Ie (W = 23.5 %)

20

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1,20 1,25 1,30 1,35 1,40 1,45 1,50

Dry density ρd (t/m3)

Crit

ical

she

ar s

tres

s τc

(Pa)

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1,20 1,25 1,30 1,35 1,40 1,45 1,50

Dry density ρd (t/m3)

Eros

ion

rate

inde

x Ie

Experimental

results

Effect of energy of compaction

3,761,75E-041,00E-012,01E-0428,511517,2Sample N° 2(1/4 Proctor)

3,951,18E-046,49E-021,36E-0465,291517,9Sample N° 1(Proctor)

IeCe(s/m)kd

(cm3/N.s)ker

(s/m)τc

(Pa)W(%)

γd(kN/m3)

3,761,75E-041,00E-012,01E-0428,511517,2Sample N° 2(1/4 Proctor)

3,951,18E-046,49E-021,36E-0465,291517,9Sample N° 1(Proctor)

IeCe(s/m)kd

(cm3/N.s)ker

(s/m)τc

(Pa)W(%)

γd(kN/m3)

Fell guidelines0

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71 10 100 1000

Eros

ion

rate

inde

x Ie

Fell DataSample N°1Sample N°2

Critical shear stress τc (Pa)

Moderatly rapid

Very rapid

Moderatly slow

Very slow

Extremely slow

Extremely rapid

1/4 Proctor

Proctor

Effect of clay content

Sample N°1

Sample N°2

Sample N°3

Sand > 50 μm (%) 44 41 33

Silt > 2 μm (%) 30 39 41

Clay < 2 μm (%) 26 20 26

γd (kN/m3) 16,7 16,7 16,7

W (%) 18 19 21

τc (Pa) 103,25 31,49 110,75

Ie 4,10 3,60 4,19

kd (cm3/N.s) 4,68E-02 1,48E-02 3,82E-01

Fell guidelines0

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71 10 100 1000

Eros

ion

rate

inde

x Ie

Fell DataSample N°1Sample N°2Sample N°3

Critical shear stress τc (Pa)

Moderatly rapid

Very rapid

Moderatly slow

Very slow

Extremely slow

Extremely rapid

Ageing effect ?

Wan et Fell guidelines0

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71 10 100 1000

Eros

ion

rate

inde

x Ie

Fell Data

ReconstitutedsamplesUndisturbedsamples

Critical shear stress tc (Pa)

Moderatly rapid

Very rapid

Moderatly slow

Very slow

Extremely slow

Extremely rapid

HET tests on naturel soils

Merci de votre attention !

Failure of Teton Dam by piping

Failure: On 3 hours only!

Contexte

Diapositive numéro 1Diapositive numéro 2Diapositive numéro 3Diapositive numéro 4Diapositive numéro 5Diapositive numéro 6Diapositive numéro 7Diapositive numéro 8Diapositive numéro 9Diapositive numéro 10Diapositive numéro 11Diapositive numéro 12Diapositive numéro 13Diapositive numéro 14Diapositive numéro 15Diapositive numéro 16Diapositive numéro 17Diapositive numéro 18