Pour mieux affirmer ses missions, le Cemagref devient Irstea www.irstea.fr Nathalie Touze-Foltz Unité Hydrosystèmes et bioprocédés Irstea [email protected]Geosynthetic clay liners: performance and long- term durability 2 Outcome Definitions Presentation of products, use and factors affecting their performance Internal factors affecting GCLs performance Quantification of the performance of GCLs towards transfers Durability of GCLs Hydraulic behaviour of GCLs in composite liners Recommendations to ensure the long-term performance of GCLs
Transcript
Pour mieux affirmer ses missions, le Cemagref devient Irstea
www.irstea.fr
Nathalie Touze-FoltzUnité Hydrosystèmes et bioprocédés
DefinitionsPresentation of products, use and factors affecting their performanceInternal factors affecting GCLs performanceQuantification of the performance of GCLs towards transfersDurability of GCLsHydraulic behaviour of GCLs in composite linersRecommendations to ensure the long-term performance of GCLs
An assembled structure of geosynthetic materials and low hydraulic conductivity earth material (clay), in the form of a manufactured sheet, used in civil engineering applications.
4
Clay geosynthetic barrier (GBR-C)(EN ISO 10318)
Factory-assembled structure of geosynthetic materials in the form of a sheet which acts as a barrier
NOTE The barrier function is essentially fulfilled by clay. It is used in contact with soil and/or other materials in geotechnical and civil engineering applications
5
Unique function
Lining
6
GCLs
Differ by manufacturingbentonite naturebentonite granularityinclusion of a coating/laminated film or not
(multicomponent GCLs)
7
Needle punched GCL
Stitch bonded GCLs
Manufacturing
8
multicomponent GCLs
Bentonite+glue
film, geomembrane or coating
geotextile
9
Examples of multicomponent GCLs
10
Use of GCLs
Landfills : 85%
11
Use of GCLs
Ponds : 10%
Along roads : 5%
12
freeze/thaw
cationexchange
hydration/desiccation
association witha geomembrane
rootsloading/hydration
puncture protection
Factors affecting the performance of GCLs
manufacturingbentonite (nature,smectite content,
granularity, mass per unit area) coating/
laminated film
internalshort-termlong-term
13
Internal factors affecting the performance of GCLs
bentonite nature•cations•smectite content
bentonite granularitymass per unit areamanufacturinginclusion of a coating/laminated film or not
swell indexwater contenttransfer properties
?
14
Bentonites
Mineralogic structure of a bentonite
Ability to absorb water between clay platelets swell, high sensitivity to cations (CEC 90meq/100g)
15
Bentonite types
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Na nat Na nat Na nat Ca act Ca act Ca act Ca nat Ca nat
LX1 LX2 LX3 LX4 LX5 LX7 LX6 LX8
Pro
porti
on
AmmoniumPotassiumSodiumMagnesiumCalcium
16
Principle : swell of 2g of bentonite in 100 ml of liquid during 24hPrinciple : swell of 2g of bentonite in 100 ml of liquid during 24h
The swell index is given in en ml / 2g of bentoniteThe swell index is given in en ml / 2g of bentonite
With distilled water With distilled water
Sodium and Ca act Sodium and Ca act bentonitesbentonites
29 ml/2g 29 ml/2g SI 36 ml/2g SI 36 ml/2g
calcium bentonitescalcium bentonites
SI 10 ml/2gSI 10 ml/2g
Results of swell index tests ASTM D 5890XP P84-703
17
Relationship between results of swell index tests and proportion of Na
Inorganic speciesDiffusion and sorption quantified for NaCl, NH4
+, Al3+, several heavy metalsSignificant attenuation at pH>6
Organic species
Diffusion and sorption of VOCs, sorption of phenolic compoundsHigh sorption on geotextiles of VOCssimilar sorption on geotextiles and bentonite for phenolic compoundsIncreased mass transport at larger temperatures (between 7 and 22°C)Increased sorption on organoclays but also increase in hydraulic conductivity
44
Durability of GCLs
45
Durability (EN ISO 10318)
Ability of a product to resist deterioration caused by weathering, mechanical, chemical, biological or other time-dependant effects, and thus to maintain the properties necessary for it to function adequately throughout its working life.
46
Mechanical effects
puncture protectionself-healinginternal erosion
47
47
Evaluation of puncture protection for long-termperformance
Impact of inappropriate protection layer on GCL thinning underneath a geomembrane
Foundation
Cou
rtesy
R. B
rach
man
GCL extrusion if a wrinkle is present
Foundation
Sand
48
Didier and Al Nassar (2002)
Quantification of the ability for self-healing(XP P84-708)
49
Description of products tested
GCL Bentonite mass per unit area (kg/m²)
Water content (%)
Thickness under 2 kPa
Free swell (ml/2g)
GCL1 4 14 7.10 19
GCL2 4.9 11 7.45 30
GCL 2
Two needlepunched GCLs
50
Flow rate vs hydraulic head for different hole sizes
51
Critical hydraulic heads
Diameter of defect (mm)
10 20 30 40
Critical hydraulic head for GCL1 (m)
14 10 6.6 2
Critical hydraulic head for GCL2 (m)
20 10.2 2.2 3.7
In the absence of other phenomena (cation exchange)
52
Internal erosion
Peggs &Olsta (1999)
•The underlayer shall support uniformely the GCL (Peggs & Olsta 1999)•The resulting confining stress will then be uniformly distributed (Peggs & Olsta 1999)•Risk fof internal erosion if it is not the case (Peggs & Olsta 1999, Rowe & Orsini 2003)•GCL fabric very important (reinforcement of carrier geotextile) (Rowe & Orsini 2003)
53
Chemical interactions
cation exchangeeffect on swell indexeffect on the hydraulic conductivityeffect of a change in hydraulic conductivity on diffusion
54
Cation exchange properties
High swelling capacity of sodium bentonites and calcium activated bentonites
NaNa++
CaCa2+2+
MgMg2+2+
KK++……
But if Na+ is exchanged by other cations……
…the ability to swell is reduced and the microstructure changes
55
Change in microstructure
Ashmawy et al. (2002)
Initial saturation withmultivalent cations
Initial saturationwith water
Pre-hydration withwater followed by permeation with multivalent cations
56
10-11
10-10
10-9
10-8
10-7
10-6
10-5
0 0.02 0.04 0.06 0.08 0.1
CaCl2 concentration (M)
Hyd
raul
ic c
ondu
ctiv
ity (m
/s)
Vasko et al. (2001)
Jo et al. (2004)
Lee et al. (2005)
Effect of the concentration of CaCl2 on the hydraulic conductivity
57
General trends observed after contact with leachate
Influence of the first hydrating medium not as critical as for single-salt speciesReal leachate is generally less aggressive than synthetic leachateRecirculation leachate is not more aggressiveLow calcium carbonate content in the bentonite recommendedPolymer treatment could improve the bentonite resistanceFor low electrical conductivity solutions, tests with NaCl and CaCl2 give a good estimation of performance
Question remaining regarding equilibrium in most tests
58
Criteria for termination of tests
– steady hydraulic conductivity– ratio of outflow to inflow of approximately unity– minimum of two pore volumes of flow (PVF) passed through the
specimen– ratios of effluent-to-influent electrical conductivity (EC) and pH
within 1.0 ±0.1
In addition, some authors recommend comparing the concentration of specific chemical species between the influent and effluent (e.g., ±10%). Benson et al. (2008): 6 to 8 PVF necessary to reach the Na+ and Al3+
equilibrium Kolstad et al. (2004): tests conducted beyond 15 to 20 PVF until each of the termination criteria previously noted were achieved.
59
Calcium activated or natural sodium bentonite?
10-12
10-11
10-10
10-9
10-8
LX1 LX2 LX3 LX4 LX5 LX7 LX6 LX8Specimen
Hyd
raul
ic c
ondu
ctiv
ity (m
/s)
NaCl 10-3MSynthetic leachateReal leachate
60
Criteria for use of GCLs in landfills
Swell index > 24 ml/2gCEC > 70 meq/100gCalcium carbonate content < 5 % in mass
61
Adequation between bentonite and leachate
green :W SLGL AL MLSS
10-8
10-7
10-9
20 30
LX1 LX2 LX5blue : black :
0 5 10 15 25Electrical conductivity (mS/cm)
Per
mitt
ivity
(s-1
)
62
Effect of a change in hydraulic conductivity on diffusion of VOCs
10-11
10-10
0 1 2 3 4 5
Number of pore volumes of flow
Hyd
raul
ic c
ondu
ctiv
ity (m
/s)
Hydraulic head: 1.2m
Hydraulic head: 0.6m
degradation of a GCL in contact with a synthetic leachate
Rosin-Paumier et al. (2011)
63
GCL1 GCL1 after cationexchange
DCM 2.9 10-10 3 10-10 3.8 10-10
DCA 2.8 10-10 3 10-10 3.6 10-10
TCE 3.9 10-10 7 10-10 7 10-10
eb 3.7 3.0 3.9
GCL1: dry mass per unit area of powdered natural sodium bentonite = 5.7kg/m². Needlepunched
Increase in the diffusion coefficient but not proportional to the increase in hydraulic conductivity. To check with other GCLs and other contaminants
Effect of a change in hydraulic conductivity on diffusion
64
Weathering effects
freeze-thawhydration-desiccationshrinkage
65
Effect of freeze-thaw
Can be evaluated through CEN TS 14418
Geosynthetic barriers — Test method for the determination of the influence of freezing-thawing cycles on the permeability of clay geosynthetic barriers
The flux through 100 mm diameter clay geosynthetic barrier specimens is determined with a flexible wall permeameter both on a specimen exposed to freezing-thawing cycles (4 cycles) and on unexposed reference specimen.Sample saturated under a pressure of (4 0.2) kPa for 48 h at constant room temperature. One sample is stored in the freezer at -5°C for 24 h.After the freezing period sample allowed to thaw at room temperature for 24 h. Sample submerged again for 24 h at room temperature.
No effect on the hydraulic conductivity even after 125 freeze-thaw cycles.No data on coupling of freeze-thaw cycles with cation exchange
66
Effect of hydration-dessication
Can be evaluated through CEN TS 14417
Geosynthetic barriers - Test method for the determination of the influence of wetting-drying cycles on the permeability of clay geosynthetic barriers
The flux through 100 mm diameter clay geosynthetic barrier specimens is determined with a flexible wall permeameter both on specimens exposed to wetting-drying cycles and on unexposed reference specimens after four cycles•Sample saturated under a pressure of (4 0.2) kPa for 48 h at constant room temperature•Drying in an oven at 110 °C for 24 h•Sample allowed to cool to room temperature for 24 h•Samples submerged again for 24 h at room temperature
No effect on the hydraulic conductivity through four wet-dry cycles(Lin & Benson, 2000)
67
67
GCL Shrinkage
courtesy R. Thiel
Mechanisms involved:
Tension in the GCL
Hydration-drying cycles
Shrinkage of geotextiles
GCL panel lateral gathering
Bentonite shrinkage due tocation exchange
68
68
Tension in the GCL
Aspect ratio = 1.0
Aspect ratio = 3.0Courtesy R. Koerner
Koerner & Koerner (2005)
69
69
Cyclic hydration and drying
After 20 cycles
Courtesy R. Thiel
Before testing
Courtesy R. ThielC
ourte
sy L
. Bos
twic
k
No significant shrinkage of geotextiles
Amount of shrinkage in the laboratory consistent with field observations
Less water less shrinkage
The presence of a woven fabric reduces the amount of shrinkage
Increased needle-punching less shrinkage
Influence of restained vs unrestrained tests
Influence of the type of GCL
Effect of the mass per unit area of bentonite (especially for law masses per unit area)
Thiel et al. (2006) Bostwick et al.(2007, 2008, 2010)
70
Recommendations for shrinkage prevention
Do not leave GM/GCL composite liners exposed (minimum 0.3m of soil)Do not use GCLs with needlepunched nonwoven geotextiles on both sides unless one is scrim reinforcedIncrease the GCL overlap Protect the exposed composite liner during its exposure (thermal blankets, geofoam)Heat tacking of seams
Bostwick et al. (2009)
71
Combined chemical interaction and hydration dessication
Results from excavationsin landfill coversin hydraulic applications
after some years in service
72
GCLs performance in dikes
1.75 m < Height < 3 m
150 m < Length < 170 m
73
GCLs samplings
sandy clay
74
Cation exchange after 3 and 5-6 years in service
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
100.00
Prop
ortio
n (%
)
Ca (%)Mg (%)K (%)NH4 (%)Na (%)
5-6 years 3 years
75
1.00E-11
1.00E-10
1.00E-09
1.00E-08
1 3 5 7 9 11
Flux
(m3/
m2/
s)
Hydraulic head (cm)
1.00E-11
1.00E-10
1.00E-09
1 3 5 7 9 11
Hyd
raul
ic c
ondu
ctiv
ity (m
/s)
Hydraulic head (cm)
Flow rate measurement after 3 years in service
load = 10 kPa
1 cm < hydraulic head < 10 cm
No swell
sorption during hydration phase
flow rate and hydraulic conductivity still acceptable
Measured according to NF P84-705
10-9
10-10
10-11
10-8
10-9
10-10
10-11
76
1.00E-06
1.00E-05
1.00E-04
0 2 4 6
Flux
(m3/
m2/
s)
Hydraulic head (cm)
1.00E-05
1.00E-04
0 1 2 3 4 5 6
Hyd
raul
icco
nduc
tivity
(m/s
)
Hydraulic head (cm)
Flow rate measurement after 5 to 6 years in service
load = 10 kPa
0,5 cm < hydraulic head < 5 cm
No swell
no significant water absorption
large flow rate and hydraulic conductivity
Measured according to NF P84-705
10-5
10-4
10-4
10-5
10-6
77
Excavations from landfill covers
France (Touze-Foltz et al., 2010)
Germany (Zanzinger and Touze-Foltz, 2009)
AB C
78Landfill A
Area repaired in 2006 according to installer
Area repaired in 2006 according to observations performed during excavation
As installed in 2003
N
2
3
6
79
Hole Dry mass per unit area of GCL specimen (kg/m2)
Water content (beginning of the test) (%)
Water content (end of the test (%))
Hydraulic conductivity(m/s)
2 4.08 48 100 1.07 10-6
3 3.95 63 112 1.71 10-6
6 3.50 37 101 6.91 10-6
10-7
10-6
10-5
10-4
0 1 2Time (hours)
Flow
rate
(m3 /m
2 /s)
GCL Hole 2
GCL Hole 3
GCL Hole 6
80
landfill B
confining soil 1.2 m thick120 cm
81
Landfill B GCL
calcium bentonite mass per unit area : 16 - 19 kg/m² water content : 70 - 80%swell index : 7 mL/2gpermittivity under 30 kPa : 5 10-9 s-1 to 8 10-9 s-1
No change in the bentonite after 6,5 yearsGood liningRoots in contact with the GCL but no penetration
82
Landfill C
Confining soil thickness : 1 m
GCLsodium bentonitemass per unit area : 10,3 kg/m² water content : 85%swell index : 7 - 8 mL/2gpermittivity under 20 kPa : 1,6 10-8 s-1 to 1,9 10-8 s-1
After 10 yearsNo influence of roots on the permittivity value Cation exchange has entirely taken placeThe GCL fulfills its function
83Upper face Lower face
Root penetration in the GCL
84
Desiccation cracks in the bentonite
When GCLs suffer cation exchange and cation exchangecracks appear they may not reseal during furtherhydrations
Case of a sodium bentonite in a GCL+ solution 0.0125M CaCl2after 4 cycles K > 4 ×10-11 m/safter 8 cycles K > 7 ×10-8 m/s
after 6 days
after 10 days(Bouazza et al. 2006)
85
0
10
20
30
40
50
[mm
/d]
01234567
[mm
/d]
0
5
10
15
20
25
[mm
/d]
0
0.5
1
1.5
2
[ mm
/d]
Precipita tion
Surface - runoff
Dra inage flow
Leakage through GCL
1998 1999 2000 2001 2002
0
10
20
30
40
50
[mm
/d]
01234567
[mm
/d]
0
5
10
15
20
25
[mm
/d]
0
0.5
1
1.5
2
[ mm
/d]
Precipita tion
Surface - runoff
Dra inage flow
Leakage through GCL
1998 1999 2000 2001 2002
Effect of desiccationcracks on leakage
From Henken-Mellies & Zanzinger 2004
86
Effect of the fraction of monovalent cations on the hydraulic conductivity
Benson & Scalia (2010)
GCLs from composite liners
Meer and Benson (2007)
GCLs from single liners
87
Effect of the water content of specimen during sampling
Benson & Scalia (2010)
88
Effect of RMD
• Mm total molarity of monovalent cations• Md total molarity of multivalent cations in the solution, • represents the relative abundance of monovalent and
multivalent cations
5.0d
m
MMRMD
89
Benson and Meer (2010)
90
90DesiccationHydration
GCLNa+ Na+ Na+Ca2+ Ca2+ Ca2+
Ca2+ Ca2+Ca2+
1mMüller-Kirchenbauer
et al. (2008) Zanzinger (2008)
Middle European climatic conditions
In contradiction with results from Meer &
Benson (2007)Wisconsin and
Georgia
Dikes, canals :0,8m of protection (sand, gravel) sufficient after 6 years in service (Fleischer & Heibaum 2008)
91
sand
drainage gecomposite
GCL
Foundation layer
Thick confining layer
waste
Cover composition
92
GCL•mass per unit area of dry sodium bentonite 4.5 kg/m²•mass per unit area of dry calcium bentonite 9 kg/m²
Protection layer•Sand has the ability to store water and feed the GCL with this water
Drainage layer•Maintain a small hydraulic head•Prevent from suction application on the GCL
Cover composition
93
Confining layer
German recommendation: 1.5 m thick as a minimum
• in dry climatic conditions (< 800 mm/a): 1.8 to 2 m with a storage function of the confining layer
• “field capacity” as large as possible (ideally 200 mm/m)• If no care to the vegetation, increase this thickness• installation without compaction • If thickness lower than 2m use a dense gravel layer at the base
to prevent from root intrusion
Cover composition
Zanzinger & Touze-Foltz (2009)
94
Hydraulic performance of GCLs in composite liners as a function of the nature of bentonite
95
95
soil liner
Geomembrane
Interface (transmissivity)
Symmetry axis
Circular hole
Leakage mechanism
Leakage
Brown et al. (1987)
96
Materials tested
Woven geotextile
Non woven geotextile
Bentonite
Needle-PunchedStitch Bonding rowsWoven geotextile
Bentonite
GCL 1.S 1.C 2.S 2.C
kGCL (m/s) 3.2 x 10-11 6.9 x 10-10 1.6 x 10-11 5.8 x 10-8
SI (cm3/2g) 34 10 33.5 <10
97
Transmissivity equipment
50 kPa
50 kPa
Compacted clay liner CCL
Effluent
200 mm
80 m
m30
0 m
m
Bottom cylinder
Granular layer
Top cylinder
Water supply
Mariotte Bottle
Bottom plate
GeomembraneGCL
Geomembrane HDPE 2mmDefect Ø 4 mm or 10 mm
GCL
Drainage layer
Compacted soil - CCLk = 8 x 10-11 m/s
COMPOSITE LINER:
98
Mariotte Bottle
Plexiglas cell
Mechanical press
Water supply (constant head)
Compacted Clay Liner
GCL
99
Results – Flow rate
1.S-4 1.C-4
2.S-4 2.C-4
10-12
10-11
10-10
10-09
10-08
10-07
10-06
0 100 200 300 400 500 600 700
Time (hours)
Flow
rate
(m3 /s
)
Significant decrease
Steady stateSlow decrease
Diameter hole in the GM = Ø 4 mm
Hydraulic Head: 0.3mConfining stress: 50 kPa
100
Results – Flow rate (2)
10-12
10-11
10-10
10-9
10-8
10-7
10-6
Flow
rate
(m3
/s)
0 50 100 150 200 250 300 350 400 450 500 550 600
Tempo (horas)
1.S-10
1.C-10
2.S-10
Diameter hole in the GM = Ø 10 mm
Similar final flow rates
Calcium bentonite: larger time to reach steady state
Time (hours)
101
Impact at field scale
GCL (kGCL, HGCL)
HCCL = 0.5 m 8 x 10-11
10-6 m/s
Attenuation layer
kSHAL = 5 m
kCCL=
kCCL in tests
10-10 m/s 10-09 m/s
kCCLrecommended(MEEDDAT 2009)
10-08 (m/s)
A B C D
102
1E-11
1E-10
1,E-10 1,E-09 1,E-08 1,E-07
Condutividade hidráulica equivalente, k EQ (m/s)
Vaz
ão, Q
(m3 /s
)
1.S 1.C
2.S 2.C
10-10
10-11
10-10 10-9 10-8 10-7
A B
C
D
1E-11
1E-10
1,E-10 1,E-09 1,E-08 1,E-07
Condutividade hidráulica equivalente, k EQ (m/s)
Vaz
ão, Q
(m3 /s
)
1.S 1.C
2.S 2.C
10-10
10-11
10-10 10-9 10-8 10-71E-11
1E-10
1,E-10 1,E-09 1,E-08 1,E-07
Condutividade hidráulica equivalente, k EQ (m/s)
Vaz
ão, Q
(m3 /s
)
1.S 1.C
2.S 2.C
10-10
10-11
10-10 10-9 10-8 10-7
A B
C
D
Equivalent Hydraulic conductivity, kEQ (m/s)
Flow
rate
, Q(m
3 /s)
103
Recommendations for ensuring the long term performance of GCLs
Mass per unit area of dry bentonite > 5kg/m²Swell index > 24 ml/2gCEC > 70 meq/100gCalcium carbonate content < 5 % in massAdaptation of bentonite to leachate to containHydration under load with low ionic strength
solutionprovide adequate underlayerProvide cover soil thick enough to prevent
from desiccation/hydration cycles
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104
Acknowledgements
Camille Barral
Who provided some slides and papers for the preparation of this presentation and time for review
Marianna Mendes
Suez Environnement, CODAHCETCO, Huesker, Naue
105
Thank you for your attention
106
References
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