Flow-rate measurements in meter-size multicomponent geosynthetic clay liners

Abstract

To quantify the flow rate through multicomponent geosynthetic clay liners (GCLs), three different meter-sized specimens from different manufacturers were characterized in a dedicated experimental column. This study allows quantification of the interface transmissivity of multicomponent GCLs when the coating or attached film is damaged over an area large enough to make edge effects negligible. For all multicomponent GCLs characterized, the coating or attached film was less than 0.7 mm thick. Steady-state results indicated flow rates ranging from 4.61 × 10−12 to 3.01 × 10−11 m3/s with interface transmissivities ranging from 1.20 × 10−11 to 7.59 × 10−11 m2/s, which are broadly in line with flow rates obtained from conventional geomembrane (GM)–GCL composite liners. Consequently, when the coating or attached film is damaged, the thickness and rigidity of the coating or attached film appears not to affect the steady-state flow rate and interface transmissivity, which leads to a good contact at the interface.

Full text

Flow-rate measurements in meter-size multicomponent geosynthetic
clay liners
H. Bannour 1,*, N. Touze-Foltz2
ABSTRACT: To quantify the flow rate through multicomponent geosynthetic clay
liners (GCLs), three different meter-sized specimens from different manufacturers were
characterized in a dedicated experimental column. This study allows quantification
of the interface transmissivity of multicomponent GCLs when the coating or
attached film is damaged over an area large enough to make edge effects negligible.
For all multicomponent GCLs characterized, the coating or attached film was less
than 0.7 mm thick. Steady-state results indicated flow rates ranging from 4.61 ×
10−12 to 3.01 × 10−11 m3/s with interface transmissivities ranging from
1.20 × 10
−11
to 7.59 × 10
−11
m
2
/s, which are broadly in line with flow rates obtained from
conventional geomembrane (GM)-GCL composite liners. Consequently, when the
coating or attached film is damaged, the thickness and rigidity of the coating or
attached film appears not to affect the steady-state flow rate and interface
transmissivity, which leads to a good contact at the interface.
KEYWORDS: Geosynthetics, environmental applications, landfill liner,
transmissivity, multicomponent geosynthetic clay liners (GCLs), experiment.
*Corresponding author
1 Irstea, HBAN Unit, Antony, France. Tel: +33-1 40 96 65 25; Fax: +33-1 40 96 62 70; E-mail: hajer.bannour@irstea.fr
2 Irstea, HBAN Unit, Antony, France. Tel: +33-1 40 96 60 39; Fax: +33-1 40 96 62 70; Email: nathalie.touze@irstea.fr
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DOI: 10.1520/STP156220120088

1. INTRODUCTION
In geotechnical and civil-engineering applications, geosynthetics are used as long-term
barriers against fluids. For example, geomembranes (GMs) and geosynthetic clay liners
(GCLs) serve as sealers in landfills, dams, dikes, ponds, etc. In the document “Recommended
Descriptions of Geosynthetics Functions, Geosynthetics Terminology, Mathematical and
Graphical Symbols” of the International Geosynthetics Society, GCLs are defined as “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.” Recently,
multicomponent GCLs have been developed, which are GCLs with a coating or attached
film. In terms of hydraulic properties, these GCLs fall between geomembranes and GCLs
(von Maubeuge et al., 2011; Cleary and Lake, 2011, Barral and Touze-Foltz, 2012).
The ASTM D35 terminology task group is currently discussing the following proposed
definitions, which might be added to the ASTM terminology standard D4439 (von Maubeuge
et al., 2011):
(i) A multicomponent GCL is a GCL with an attached film, coating, or membrane
decreasing the hydraulic conductivity or protecting the clay core or both,
(ii) An adhered GCL is a GCL product in which the clay component is bonded to a film
or membrane by adhesion, and
(iii) A coated GCL is a GCL product with at least one layer of a synthetic substance
applied to the GCL as a fluid and allowed to solidify (von Maubeuge et al. 2011).
To ensure clarity, this terminology is adopted in this paper.
Multicomponent GCLs have recently been put on the market despite no devices existing that
can characterize them especially as regards transfer of pollutants through the GCLs. The
objective of this paper is to determine the hydraulic performance (i.e., flow rate and interface
transmissivity) of multicomponent GCLs whose coating or attached film has a circular hole.
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DOI: 10.1520/STP156220120088

Experiments using various GCL configurations have determined the flow rates in GM/GCL
composite liners (Harpur et al., 1993; Barroso et al., 2006a; 2008; 2010; Mendes et al. 2010;
Rowe and Abdellaty, 2012; Bannour et al., 2013a; 2013b). In addition, the effect of contact
quality at the interface between GM and GCL was evaluated for textured GMs in contact with
GCLs (Barroso et al., 2008; Bannour et al., 2013a). The experimental results were
reproducible and showed that the texture has little impact on steady-state flow rates. Other
research evaluated how the nature of the bentonite, sodium, or calcium bentonite and the
structure of the GCL affected flow rates in the GCL (Mendes et al., 2010) and concluded that
the nature of the bentonite and the manufacturing process of the GCLs studied did not affect
the GM/GCL interface transmissivity under conditions of steady-state flow.
For multicomponent GCLs, Barral and Touze-Foltz (2012) proposed an experimental device
that quantified the flow rate through multicomponent GCLs with coatings or attached films
that were not damaged. This study showed that flow rates for multicomponent GCLs from
two different manufacturers are one order of magnitude larger than flow rates usually
measured for virgin GMs (i.e., 10
−5
m
3
/m
2
/d) but are significantly less than the flow rate for
typical GCLs.
A preliminary study considered the case in which the coating or laminated film is damaged.
This study considered the decimeter scale in quantifying the flow rate and the resulting
transmissivity in a multicomponent GCL (Bannour et al., 2013b). Two of the multicomponent
GCLs tested, with an attached film at their surface, had to be prehydrated under a low hydraulic
head to ensure that the flow rates could be measured and would decrease with time as usually
occurs in composite liners containing a GCL. To improve the analysis of the results, additional
experiments were undertaken in which a GM was added on top of the multicomponent GCLs.
This addition increased the rigidity, thereby improving the distribution of the load, which
consisted of the top granular plate and the 50 kPa of confining stress. The addition of the GM
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led to a decrease in flow rates and interface transmissivity with respect to the case with no GM.
Results obtained at the decimeter scale raised the question of whether a scaling effect, which
was not previously observed in GM/GCL composite liners, could explain the different flow
rates and interface transmissivities (Touze-Foltz et al., 2006).
The present study quantifies the meter-scale flow rate and resulting interface transmissivity of a
multicomponent GCL whose film or coating is damaged. To determine how the thickness of the
coating or attached film affects flow rates and interface transmissivity, the meter-scale results
are compared with previously obtained decimeter-scale results. Working on the meter scale is
appropriate because the area studied is close to that encountered by GM/GCL composite
liners in real situations of barriers in landfill areas, where edge effects are negligible (Touze-
Foltz et al., 2006).
The remainder of this paper begins with a presentation of the materials characterized in this
study and outlines the large-scale experimental procedure. Next, the flow rates, interface
transmissivity, and water-content distribution in multicomponent GCLs are presented,
discussed, and compared with results obtained from decimeter-scale measurements done on
the same multicomponent GCLs and with published results of flow rate and interface
transmissivity in composite liners with GCLs.
2. EXPERIMENTS
2.1. Materials and methods
2.1.1.
Elastomer plate
A 0.06-m-thick elastomeric plate was used at the bottom of the experimental column as a
substitute for the compacted clay liner (CCL) conventionally used under the GCL in interface
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transmissivity experiments. It consists in a polymetric plate presenting a higher elasticityand
is similar to the one used by Stoltz et al. (2013) in puncture-protection experiments.
2.1.2.
Multicomponent GCLs
Three different multicomponent GCLs, each from different manufacturers, were measured in
this study. All three were made from a needle-punched GCL with the addition of either a
coating or a film.
The first multicomponent GCL (GCL 1) is a coated GCL. The polyolefin polymer coating is
added in the fluid state directly onto the woven component of the GCL. This strategy allows the
polymer coating to penetrate into the woven structure, surround the needle-punched fibers from
the nonwoven carrier geotextile, and attach firmly, uniformly, and in a directionally
independent manner to the entire woven GCL component. GCLs 2 and 3 were manufactured
with an attached film (Figure 1). Details of the various multicomponent GCLs are given in
Table 1, which includes cover and carrier geotextile types, bonding types, film or coating
thickness according to EN ISO 9863-1, total dry mass per unit area of the coating or the
attached film and, finally, measured total dry mass per unit area of specimen (EN ISO 14149).
After the experiments, the mass per unit area of dry bentonite in the specimens was measured.
To obtain the mass per unit area of geosynthetics, results from three 0.09-m-diameter specimens
taken from the remainder of the sample (i.e., the part not previously characterized) were
averaged after removing the bentonite and cleaning the geosynthetics.
Figure 1 shows the surface of the coating or the attached film on top of each multicomponent
GCL. The wrinkling of the film varies depending on the product used. No wrinkling occurs in
the attached film of GCL 2. The initial water content of all multicomponent GCLs characterized
was approximately 10%.
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2.1.3.
Protective geotextile
To protect the coating or attached film from puncturing during installation of the granular
layer, a nonwoven geotextile was put on the top of the multicomponent GCLs. To adequately
protect the GM liner, Stoltz et al. (2013) suggest a minimum mass per unit area of geotextile
of 1000 g/m
2
. For the present experiments, a protective geotextile with a mass per unit area of
1200 g/m
2
was selected for the experimental column used. For experiments performed at the
metric scale, the protective geotextile was placed on top of the multicomponent GCLs to inhibit
penetration by the 0.25-m-thick gravel layer. To reproduce the same experimental conditions as
used at the decimeter scale, an additional experiment was performed on GCL 2 in which the
geotextile was not added on the top of the multicomponent GCL; no significant changes in
transient or steady-state flow rate were observed. This observation shows that the protective
geotextile, which was added to prevent penetration of the GM by the gravel layer, does not
influence the flow rate of the multicomponent GCL.
2.1.4.
Granular layer
A 0.25-m-thick drainage layer, consisting of 25- to 35-mm-diameter gravel, was used on top
of the protective geotextile over thickness to transfer the load from the mechanical press.
2.2. Meter-scale apparatus and experimental setup
The experimental setup consisted of a 1-m-diameter cell as previously described by Cartaud et
al. (2005a) and Touze Foltz et al. (2006). The cell is composed of three parts (see Figure 2): (a)
a bottom part with a round base plate fixed to the beam of a hydraulic press that applies a
compressive stress; (b) an intermediate 1-m-diameter cylinder 0.3 m high fixed to the base plate
for accommodating the simulated liner and granular layer; and (c) a stainless-steel plate for
applying the compressive stress. An elastomeric plate was placed at the bottom of the cell and a
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1-m-diameter multicomponent GCL specimen was placed above the plate. A circular 4-mm-
diameter hole was cut in the center of the coating or attached film of the multicomponent GCL.
A special “Y” connection was glued over the discontinuity in the coating or attached film, and a
pipe was inserted in each branch of this connection: one pipe was connected to a Mariotte bottle
to allow flow-rate measurements and the other pipe was used as a purge (Figure 3). Next, a
1200 g/m
2
geotextile was placed above the multicomponent GCL to prevent it from being
penetrated by the gravel. The stainless-steel plate was placed above the gravel layer and a
normal 50 kPa compressive stress was applied by the hydraulic press. Finally, the liquid supply
was activated and experiments started. The hydraulic head is applied vertically at the level of
the hole in the geomembrane. Then the flow takes place horizontally in the interface and jointly
vertically in the GCL. To compare measured flow rates with published values, experiments
were carried out with a 0.3 m hydraulic head.
3. RESULTS AND DISCUSSION
3.1. Steady-state flow rate, interface transmissivity, and water-content
distribution
Figure 4 shows the flow-rate dynamics found experimentally for the three multicomponent
GCLs. When applying the 0.3m hydraulic head using the Mariotte bottle, the water flows
directly in the Y connection glued over the hole. It penetrates the interface between the coating
or attached film and the underlying GCL before hydrating the GCL. The flow rate was obtained
only upstream of the cell, which shows that the meter scale of the experiment was sufficient to
appropriately reproduce, with no edge effects, a real multicomponent GCL in the liner area.
The measured flow rates decreased gradually to steady-state values of 4.61 × 10
−12
,
4.36 × 10
−12
, and 3.01 × 10
−11
m
3
/s for multicomponent GCL 1, GCL 2, and GCL3,
respectively. Steady-state has to be understood here as corresponding to stabilization of the flow
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rate at the upstream side. The interface transmissivities was back calculated by using the
analytical solution developed by Touze Foltz et al. (1999) in the case of a circular defect in the
GM. This solution assumes that (i) the interface transmissivity is uniform so that the wetted
area obtained is circular, (ii) the liquid flow in the transmissive layer is radial, (iii) the flow
occurs under steady-state conditions, (iv) the CCL, the GCL, and the GM-GCL interface are
saturated, and (v) the additional flow through the passive barrier (CCL + GCL) is one
dimensional and vertical. The final flow rates (steady-state conditions) measured in
transmissivity experiments were used in Equation 1:
( ) ( )
[ ]
0101
2
0
2
2
0rBKrIAr
s
H
d
w
h
s
krQ
αααθππ
−−
+
= (1)
s
s
d
k
θ
α
= (2)
(
)
(
)
(
)
(
)
( ) ( ) ( ) ( )
000000
0000
rIRKRIrK rKRKHRKh
A
sw
αααα
α
α
α
−
−
+
−=
(3)
(
)
(
)
(
)
(
)
( ) ( ) ( ) ( )
000000
0000
rIRKRIrK rIRIHRKh
B
sw
αααα
α
α
α
−
−
+
=
(4)
with
(
)
(
)
0
11 =−+ s
HRBKRAI
αα
(5)
The interface transmissivity
θ
and the radius of the wetted area R were calculated using a
parametric study assuming that there is no flow at R (Q(R)=0). They correspond to
interpretations as the assumption that the geometry is axisymmetric is made.
Interface transmissivity calculated using the analytical solution were 2.10 × 10
−11
, 8.97 × 10
−11
,
and 7.59 × 10
−11
m
2
/s, for multicomponent GCL 1, GCL 2, and GCL3 (Table 2), respectively.
At the end of the experiment, the water-content distribution in the multicomponent GCLs was
quantified and the results, which are based on the sampling performed, are plotted in Figure 5.
After flow-rate stabilization, the water-content distribution was measured in 37 0.1-m-
diameter multicomponent specimens, according to the scheme presented in Figure 6. This
method of sampling GCLs to determine the water content repartition is consistent with that
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presented by Touze-Foltz et al. (2006). The radius of the wetted area calculated by using the
analytical solution developed by Touze Foltz et al. (1999) were 0.05, 0.14, and 0.28 m for
multicomponent GCL 1, GCL 2 and GCL3, respectively.
3.2. Performance of multicomponent GCLs
Despite a mass per unit area of 4.40 kg/m
2
, multicomponent GCL 1 had small steady-state flow
rates (
Q
= 4.61 × 10
−12
m
3
/s), which is attributed to the coating that is directly laminated to the
covering geotextile of the multicomponent GCL (assuming good contact at the interface). As
shown in Figure 4, multicomponent GCL 3 had lower transient and steady-state flow rates on
the meter scale (
Q
= 3.01 × 10
−11
m
3
/s) compared with multicomponent GCL 2
(
Q
= 4.36 × 10
−12
m
3
/s), despite both multicomponent GCLs having a surface film attached by
the same production process (Table 2). Compared with multicomponent GCL 2, GCL 3 had a
larger wetted-area radius (0.28 m vs 0.14 m) and water-uptake capacity, which may be
explained by (i) the mass per unit area of each specimen (6.44 kg/m
2
for GCL 2 vs 4.27 kg/m
2
for GCL 3); (ii) the presence of wrinkles on the attached film, which allows water to migrate
more easily (this was the case in particular for high transient flow rates, i.e., flow rates
approximately one to two orders of magnitude higher than those obtained with
multicomponent GCL 1 and 2), and (iii) the possible influence of swelling-index measurements
taken on multicomponent GCL 2 and 3 (these were done to evaluate the swelling of the
bentonite part of the GCL and could have influenced the contact quality at the interface between
the GCL and attached film). The results show that multicomponent GCL 2 swells more than
multicomponent GCL 3 (measurements performed following XP P 84-703 gave swell indices of
29 cm
3
/2g for GCL 2 and 24 cm
3
/2g for GCL 3). These observations means that
multicomponent GCL 2 benefits from better interface contact than multicomponent GCL 3,
which is attributed to a better contact between the attached film and the cover geotextile of the
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multicomponent GCL. The superior contact is likely due to greater swelling when the bentonite
hydrates and the more uniform distribution of bentonite in GCL 2, as determined by the greater
mass per unit area (Bostwick et al. 2010).
3.3. Decimeter- vs meter-scale flow-rate dynamics along multicomponent
GCL interfaces
Figure 7 compares the decimeter- and meter-scale flow-rate dynamics in multicomponent
GCLs from Bannour et al. (2013b). The meter-scale steady-state results are one order of
magnitude less the decimeter-scale results, as seen in Table 5. These results were obtained with
steady-state flow rates ranging from 4.61 × 10
−12
to 3.01 × 10
−11
m
3
/s for the meter-scale
experiments and from 1.53 × 10
−11
and 2.18 × 10
−10
m
3
/s for the decimeter-scale
experiments. This observation shows the importance of the effect of scale for multicomponent
GCLs: a sufficiently large area must be studied (i) to minimize the edge effects observed at the
decimeter scale, which may generate preferential flow paths in the absence of nonuniformities
such as wrinkles in the attached film, and (ii) so that the radius of the experimental device is
consistent with the wetted area.
3.4. Comparison with GM-GCL composite liner
Decimeter-scale results obtained by Bannour et al. (2013b) highlight the fact that the flow rate
was influenced by the thickness of the polymeric component (i.e., the coating or attached film
with or without an additional 2-mm-thick high-density polyethylene “HDPE” GM): the flow
rate was one order of magnitude less for a 2-mm-thick HDPE GM on the top of the
multicomponent GCL than for no GM. Decimeter-scale flow rates obtained with
multicomponent GCLs were one to two orders of magnitude larger compared with those for a
GM-GCL composite liner.
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Figure 8 compares meter-scale flow-rate dynamics along multicomponent GCL interfaces
obtained in this study with results from the study of Touze Foltz et al. (2006) on conventional
GM-GCL composite liners. Steady-state flow rates are comparable for both configurations;
the average flow rate for the GM/GCL composite liner is 4.09 × 10
−12
m
3
/s. This finding
shows that, as found in the meter-scale experiment with a geomembrane, neither the thickness
nor the rigidity of the coating or attached film significantly influences flow rates.
Thus, even if the reduced thickness of the coating or attached film decreases rigidity in
comparison with the 2-mm-thick geomembrane and decreases the uniformity of load
transmission by the granular layer, no impact on flow rate is detected. This phenomenon is
probably connected to the bentonite swelling sufficiently to reduce the interface thickness;
similar to what occurs in the GM/GCL composite liner.
These findings emphasize that, to quantify flow rates in multicomponent GCLs with the
coating or attached film exhibiting a hole on the meter scale, it is necessary to perform meter-
scale experiments.
3.5. Synthesis of transmissivity values in GM-GCL composites liners and
multicomponent GCLs
Figure 9 gives an overview of published interface transmissivity data and data from this study.
For meter-scale experiments with multicomponent GCLs, all data fall under the GM/GCL
contact condition defined by Touze Foltz and Barroso (2006), which links the interface
transmissivity
θ
to the hydraulic conductivity
kGCL
of the GCL by using Equation 1:
GCL
k
1010
log7155.02322.2log +−=
θ
(1)
Results obtained for the interface transmissivity are broadly in line with the interface
transmissivity found in previous studies that used conventional GM/GCL composite liners. This
correlation suggests that, for meter-scale experiments, the thickness and rigidity of the coating
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or attached film does not significantly influence the interface transmissivity when the coating
or attached film is damaged. Consequently, for a 4-mm-diameter hole, the characteristics of
advective transfers through damaged multicomponent GCLs are identical to those through
conventional GM/GCL composite liners.
Note, however, that this result does not imply that all aspects of the performance are identical.
In fact, the flow rate through an undamaged multicomponent GCLs is one order of magnitude
larger than that through an undamaged GM (Barral et al., 2012). In addition, when addressing
performance, other considerations regarding mechanical performance, chemical compatibility,
and durability are imposed.
4. CONCLUSION
The purpose of this study was to compare the hydraulic performance of a multicomponent GCL
with that of a conventional GM-GCL composite liner. To this end, the flow rate and interface
transmissivity in multicomponent GCLs was evaluated for the case of a damaged coating or
attached film.
For the surface area of the multicomponent GCL to be representative of a real situation, meter-
scale flow-rate experiments were performed, and the following results were obtained:
- To measure flow rates through multicomponent GCLs, the meter scale is better than the
decimeter scale because it avoids edge effects that are likely to influence the
experimental results. Consequently, the area studied is close to that encountered by
GM/GCL composite liners in real situations of barriers in landfill areas, where edge
effects are negligible.
- The meter-scale steady-state flow rate and interface transmissivity obtained were
broadly in line with flow rates obtained in previous studies that used conventional
composite liner GM/GCL. This correlation emphasizes the fact that, for flow-rate
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measurements through a multicomponent GCL with a damaged coating or attached
film, the thickness and rigidity of the coating or attached film does not affect the
hydraulic behavior of the multicomponent GCL in comparison with conventional
composite liners (GM/GCL).
- The swell index and mass per unit area of bentonite in multicomponent GCLs influence
the flow rate when a film is attached (glued) to the cover geotextile of the GCL. It is
thus important for the mass of bentonite in the GCL to be sufficient so that the swelling
capacity of samples leads to better contact at the interface and better performance of the
multicomponent GCL.
ACKNOWLEDGMENTS
This study was financed by IRSTEA, Antony, France. The authors gratefully acknowledge
CETCO and NAUE for providing the multicomponent GCLs liners used in this study.
NOTATIONS
Basic SI units are given in parentheses.
Q the flow rate (m3/s)
r0 the circular-defect radius (m)
mf Film or coating measured total dry mass per unit area (kg/m2)
R radius of the wetted area (m)
ef Film or coating thickness (mm)
kGCL the hydraulic conductivity of the liner GCL (m/s)
ks the hydraulic conductivity of the liner GCL + CCL (m/s)
Hw the hydraulic head (m)
Hs the thickness of the soil component of the GCL + CCL composite liner (m)
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d the thickness (m) of the GCL + CCL liner (m)
θ interface transmissivity (m2/s)
α,A, B parameters (dimensionless)
I1, K1 first-order modified Bessel functions
I0,K0 zeroth-order modified Bessel functions (dimenionless)
ω water content (%)
ABBREVIATIONS
CCL compacted clay liner
GCL geosynthetic clay liner
GM geomembrane
HDPE high-density polyethylene
REFERENCES
AFNOR 2002 XP P 84-703 Bentonitic geosynthetics — Determination of the swelling
capacity of clay in bentonitic geosynthetics.
AFNOR 2003 EN ISO 14149 Geosynthetics: — test methods for measuring Mass per Unit
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pressure, part 1: individuals layers.
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Transmissivity Measurement in Multicomponent Geosynthetic Clay Liners. Current and
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DOI: 10.1520/STP156220120088

Table 1 Multicomponent GCLs used in this study.
Multicomponent
GCL
Cover GTX Carrier GTX Bonding Film or
coating
thickness (m)
Film or coating
measured total
dry mass per
unit area
(kg/m2)
Measured total
dry mass per
unit area of
specimen
(kg/m2)
1 Woven Nonwoven Coated 0.0004 < ef <
0.0007
0.25 < mf < 0.4 4.40
2 Nonwoven Woven Attached
(glued)
~0.00045 ~0.2 6.44
3 Woven Nonwoven Attached
(glued)
~0.00025 ~0.2 4.27
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Table 2 Flow rate, hydraulic conductivity, and interface transmissivity measured and
calculated by using the analytical solution for steady-state meter-scale conditions. Also shown
are published results related to multicomponent GCLs.
Multicomponent GCL
Q (m
3
/s) K
GCL
(m/s) θ (m
2
/s) Radius of
wetted area R
(m)
GCL 1 (m) 4.61
×
10
−
12
2.08
×
10
−
11
1.20
×
10
−
11
0.05
GCL 2 (m) 4.36
×
10
−
12
2.66
×
10
−
11
8.97
×
10
−
11
0.14
GCL 3 (m) 3.01
×
10
−
11
2.08
×
10
−
11
7.59
×
10
−
11
0.28
Bannour et al. (2013b) GCL 1 (dm) 1.73
×
10
−
11
2.08
×
10
−
11
3.48
×
10
−
11
0.1
Bannour et al. (2013b) GCL 2 (dm) 1.53
×
10
−
11
2.66
×
10
−
11
3.07
×
10
−
11
0.1
Bannour et al. (2013b) GCL 3 (dm) 2.18
×
10
−
10
2.08
×
10
−
11
5.46
×
10
−
11
0.1
Bannour et al. (2013b) GCL 1 (dm)+GM 1.39
×
10
−
11
2.08
×
10
−
11
2.78
×
10
−
11
0.1
Bannour et al. (2013b) GCL 2 (dm)+GM 2.17
×
10
−
11
2.66
×
10
−
11
4.41
×
10
−
11
0.1
Bannour et al. (2013b) GCL 3 (dm)+GM 1.31
×
10
−
11
2.08
×
10
−
11
2.60
×
10
−
11
0.1
Q
is the steady-state flow rate (m
3
/s), K
GCL
is the steady-state
hydraulic conductivity (m/s);
θ
is the interface transmissivity
(m
2
/s) calculated by using the analytical solution; and
R
is the radius of the wetted area (m).
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DOI: 10.1520/STP156220120088

(a) (b)
(c)
Figure 1: Photographs of surface of the various multicomponent GCLs studied: (a) GCL 1,
(b) GCL 2, (c) GCL 3.
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Confining
stress Mariotte
bottle
0.25 m
1
m
Hydraulic
head = 0.3m
Legend:
Downstream
flow
Granular layer
Multicomponent
GCL
Elastomer Plate
Flow
direction
Figure 2: Column-test apparatus modified from Touze Foltz et al. (2006)
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Connection
with Mariotte
bottle
Purge
Flow direction
Legend:
Coating or attached
film
GCL
Multicomponent
GCL
Elastomer plate
Figure 3: Principle of “Y” connection.
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10-6
10-7
10-8
10-9
10-10
10-11
10-12
10-13
Figure 4: Dynamics of flow rate along multicomponent GCLs interfaces obtained by the
meter-scale apparatus
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X (m)
Y (m)
Water content ɷ (%)
30
26
22
18
14
10
0.6
0.4
0.2
0
0 0.2 0.4 0.6
(a)
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Water content ɷ (%)
0 0.2 0.4 0.6
0.6
0.4
0.2
0
60
50
40
30
20
10
X (m)
Y (m)
(b)
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Water content ɷ (%)
0 0.2 0.4 0.6
0.6
0.4
0.2
0
X (m)
Y (m)
100
80
60
40
20
(c)
Figure 5: Water-content distribution in multicomponent GCLs after meter-scale experiment:
(a) GCL 1, (b) GCL 2, (c) GCL 3.
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2-1
2-2
2-4
2-3
3-1
3-2
3-3 3-4
6-1
6-2 6-3
6-4
9-2
9-3
9-4
9-1
8-4
8-3
8-1
8-2
7-4
7-3
7-
17-2
4-4
4-3
4-2
4-1
4-4
1-3
1-2
1-1
5-3
5-1 5-2
5-4 5-5
Multicomponent GCL
specimen Sampling plan
Figure 6: Cartography of 0.1-m-diameter GCL specimens.
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10-6
10-7
10-8
10-9
10-10
10-11
10-12
10-13
Figure 7: Comparison of decimeter- and meter-scale flow-rate dynamics along
multicomponent GCL interfaces.
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10-6
10-7
10-8
10-9
10-10
10-11
10-12
10-13
Figure 8: Comparison of meter-scale flow-rate dynamics along multicomponent GCL
interfaces obtained in this study at metric scale with published results based on conventional
GM-GCL composite liners.
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0
0
0
0
0
0
0
0
1E-121E-111E-101E-091E-081E-071E-061E-05
Hydraulic conductivity (m/s)
GM-GCL
Poor
Good
Excellent
10-6
10-7
10-8
10-9
10-10
10-11
10-12
10-13
10-12 10-11 10-10 10-9 10-8 10-7 10-6 10-5
Interface transmissivity,
θ(m2/s)
Figure 9: Overview of published transmissivity data for GCLs in contact with GMs and for
multicomponent GCLs.
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DOI: 10.1520/STP156220120088