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Effect of the waste pressure on fluid migration through geomembrane defects
Abstract
Composite liners consisting of a geomembrane (GM), with a circular hole, a geosynthetic clay liner (GCL) and a compacted clay liner (CCL) were studied through laboratory tests. Flow rates at the interface between the GM and the GCL were measured and the correspondent interface transmissivities were calculated. The tests conducted aimed at studying the influence of the waste pressure on flow rates through composite liners due to defects in the GM. Several confining pressures, ranging from 25 to 200 kPa, were used. Results obtained indicate that, for the range of pressures used, the increase in waste pressure has a slight influence on flow rate and on correspondent interface transmissivity.
... Various situations were tested in the past to evaluate the effect of a smooth GM in contact with the GCL [5][6][7]. It has been verified that under steady-state conditions, the most significant fraction of the flow takes place along the interface between the GM and the cover geotextile of the GCL, through the cover geotextile, and along gaps between the cover geotextile of the GCL and the bentonite [5]. ...
... A less important amount of fluid percolates through the bentonite and below the GCL. The influence of the hydraulic head, pre-hydration of the GCL, and confining stress on the GM-GCL interface transmissivity has also been investigated [6,7]. The results obtained by those authors showed that it is difficult to establish general trends expressing the influence of pre-hydration, confining stress, and hydraulic head on the interface transmissivity. ...
... Transmissivity tests are carried out in an apparatus specially designed to measure the flow rate in a composite liner, as shown in Fig. 2. As previously described in the literature [6][7][8][9][10][11][12], it consists of a Plexiglas cell basically composed by four parts: (i) a bottom plate which supports the soil and applies the confining stress; (ii) a 200-mm-inside-diameter base cylinder, 80 mm high, to accommodate the compacted base soil and the mineral part of the multicomponent GCL specimen; (iii) a top coarse granular drainage layer; and (iv) an upper cylinder that accommodates the granular layer. To assemble the test, Note: K CCL , hydraulic conductivity of the soil composing the CCL; PI, plasticity index; x L , liquid limit; ...
Three different multicomponent geosynthetic clay liners (GCLs) from different manufacturers are tested in a transmissivity cell with a new testing procedure to quantify the flow rate and the interface transmissivity between the coating or attached film presenting a hole and the upper geotextile of the GCL. The testing device was previously used in studies aiming to evaluate the interface transmissivity between a damaged geomembrane (GM) and a regular GCL. Different results are obtained regarding the evolution with the time of the flow rate ranging from 1.7310 11 m3/s to 2.1810 10 m3/s at steady state, which is on average in the range of flow rate results obtained with a GM–GCL composite liner. Additional tests performed by adding a GM on top give lower values of flow rates. This shows the importance of the film or coating rigidity for decreasing flow rate and insuring a better quality contact at the interface.
... Issues concerning leakage through composite liners comprised of a geomembrane (GMB) as a primary liner and a GCL as a secondary liner due to defects in the GMB (i.e. holes) and/or holes in wrinkles in the GMB have been examined by a number of researchers (Giroud and Bonaparte 1989;Harpur et al. 1993;Giroud 1997;Rowe 1998Rowe , 2005Rowe , 2012Cartaud et al. 2005;Take et al. 2007; Barroso et al. 2008Barroso et al. , 2010Saidi et al. 2008;Mendes et al. 2010a;Chappel et al. 2012aChappel et al. , 2012bEl-Zein et al. 2012;Rowe and Abdelatty 2012a;Rowe et al. 2012). The findings from this research are helpful in understanding the factors that may affect the leakage through a concrete/ GCL composite liner; however, to the authors' knowledge, the factors affecting the leakage through the composite concrete/GCL liner have not been previously reported. ...
... The same conclusion regarding the effect of the hole size in a GMB on Ł was reported by Koerner and Koerner (2002). Barroso et al. (2010) evaluated the GMB/GCL interface transmissivity by performing a series of leakage tests through laboratory-simulated composite liners comprised of (from top to bottom) a GMB with a circular hole, a needle-punched GCL with nonwoven cover GTX, and a compacted clay liner (CCL) under six different confining pressures ranging from 25 to 200 kPa. Test results indicated that the increase in confining pressures has a negligible practical impact on Ł for the pressures examined. ...
... The average Ł under 1.0 m head was 2.2-5.3 3 10 À11 m 2 /s after 144-230 days of testing (Table 5) with an overall average Ł of about 3.8 3 10 À11 m 2 /s. These Ł values are of a similar magnitude to those obtained by Barroso et al. (2008Barroso et al. ( , 2010 ...
The performance of four geosynthetic clay liners (GCLs) used as a hydraulic barrier below concrete-lined sewage treatment lagoons was examined based on a series of laboratory tests aimed at measuring: (i) the lateral flow of synthetic wastewater through the interface between each GCL product and a 0.1 m thick cast-in-place concrete above the GCL over a 14-month period and, from this data, calculating the concrete/GCL interface transmissivity (θ); and (ii) the hydraulic conductivity (k) of the GCLs below poured concrete when exposed to (iia) synthetic wastewater under isothermal conditions, or (iib) a series of wet-dry and/or cool-heat cycles for up to 12 months. The four GCLs have either sodium or polymer-enhanced sodium bentonite, and either granular or powdered bentonite. When the wastewater head above the GCL was 1.0 m (stress on concrete, s= 10 kPa), θ for the GCL with granular sodium bentonite was 4 × 10-11 m2/s. For the same GCL, when the head increased to 2.5 m (s = 25 kPa), the value of Ł was reduced by about one order of magnitude to 2 3 10[1]12 m2/s. For the GCL which has polymer-enhanced granular bentonite, the value of θ was similar to (and possibly lower than) that for the GCL with untreated granular bentonite. For the GCL with powdered bentonite and cover geotextile impregnated with 1280 g/m2 of bentonite, the values of Ł were 2 × 10-12 and 4 × 10-13 m2/s at 1.0 and 2.5 m head, respectively. With a reduction in the amount of the impregnated powdered bentonite in the cover geotextile to 840 g/m2, θ was 1 to 9 ×10-12 m2/s. The lowest k (3.2 ×10-11 m/s) for a GCL below concrete and exposed to wastewater under isothermal conditions was measured for the GCL with polymer-enhanced granular bentonite, whereas the highest value of k (1.9 ×10-10 m/s) was for the GCL with standard granular bentonite. Under 0.5 m head and 3 kPa stress, the k of the GCL below concrete and exposed to wet-dry cycles was 1.2-2.6 times the k of the GCL exposed to wastewater under isothermal conditions. Analytical calculations for the leakage through concrete/ GCL liners for the four GCLs showed that the leakage was below the allowable limits specified by the Australian, British, and American standards.
... Those parameters are identical to the ones previously used in other experiments from the literature, for the sake of comparison. So that results obtained experimentally could be compared with results from the literature for the same type of GMB (Barroso, Lopes, & Bergamini, 2010; Barroso, Touze-Foltz, & von Maubeuge, 2008; Barroso et al., 2006; Mendes et al., 2010), specimens from the same smooth HDPE GMB were used with all GCLs. The initial properties of the GMB are summarised in Table 2. ...
... Experiments were carried out in an apparatus specially designed to measure the flow rate in a composite liner or in multicomponent GCLs (see Figure 2and Barroso et al., 2006; Barroso et al., 2010; Barroso et al., 2008; Bannour, Barral, & Touze-Foltz, 2013a; Bannour, Touze-Foltz, Courté, & von Maubeuge, 2013b; Mendes et al., 2010; Touze-Foltz, 2002). GCL specimens were cut to the internal diameter of the cell using a cutting shoe and did not experience any special preparation. ...
... Water Figure 2. Apparatus for measuring interface transmissivity (after Bannour et al., 2013aBannour et al., , 2013b Barroso et al., 2006; Barroso et al., 2008; Barroso et al., 2010; Mendes et al., 2010; Touze Foltz, 2002). The flow rate through composite liners containing the exhumed and altered GCLs as well as the virgin GCLs exhibited two different trends: ...
This study evaluates how alteration of geosynthetic clay liners (GCLs) affects the hydraulic behaviour of a composite liner when the geomembrane presenting a hole is overlying a GCL. Interface transmissivity experiments were performed on GCL specimens that were exhumed from field sites. The results reveal different trends in the flow rates, which decrease differently to their steady state values. The steady state flow rates obtained and the calculated interface transmissivities are of the same order of magnitude as results obtained with a virgin GCL. The transient flow rate results are discussed in relation with the GCLs parameters. Based on these results, a new equation is derived that links interface transmissivity to the hydraulic conductivity of GCLs that have been altered by the environment. Considering large transient flow rates in calculations result in a greater leakage volume penetrating the liner when compared to calculations of infiltrated volumes considering only steady state leakage volume for a period of time of 1, 10 or 30 years. From a practical point of view, this suggests the introduction of a factor of safety of 1.67 when calculating the flow rate in composite liners in order to take into account the alteration by the environment of GCLs.
... The results for GM-GCL interface transmissivity reported by Harpur et al. (1993) at 7 kPa (a stress relevant to some lagoon applications) and 70 kPa are given in Table 6 together with values for a stress at 50 kPa reported by Barroso et al. (2008Barroso et al. ( , 2010 and Mendes et al. (2010). ...
... Barroso et al. (2008) examined the effect of the GM surface on transmissivity, examining one smooth and three different textured GMs in contact with the same GCL (N-F; Table 6) and the range of transmissivities was relatively small (1.4 × 10 -11 to 3.7 × 10 -11 m 2 /s at 50 kPa) with an average of 2.5 × 10 -11 m 2 /s. Barroso et al. (2010) studied the effect of confining stress on interface transmissivity between a smooth GM and a GCL with a nonwoven cover geotextile in contact with the GM. Based on five tests at stresses between 25 and 200 kPa, they found very little difference with the highest value of q = 1.4 × 10 -11 m 2 /s at 25 kPa and values between 7.8 × 10 -12 and 1.2 × 10 -11 m 2 /s between 50 and 200 kPa. ...
... b Barroso et al. (2008). c Barroso et al. (2010). In comparison, for a composite liner with a similar CCL, the calculated leakage was only 2 and 2.6 lphd for a small and large hole, respectively (Table 8). ...
The factors that may affect short-term leakage through composite liners are examined. It is shown that the leakage through composite liners is only a very small fraction of that expected for either a geomembrane (GM) or clay liner (CL) alone. However, the calculated leakage through holes in a GM in direct contact with a clay liner is typically substantially smaller than that actually observed in the field. It is shown that calculated leakage taking account of typical connected wrinkle lengths observed in the field explains the observed field leakage through composite liners. Provided that care is taken to avoid excessive connected wrinkle lengths, the leakage through composite liners is very small compared to a typical GM or CL alone. It is shown that the leakage through composite liners with a geosynthetic clay liner (GCL) is typically much less than for composite liners with a compacted clay liner (CCL). Finally, factors that will affect long-term leakage through composite liners are discussed. It is concluded that composite liners have performed extremely well in field applications for a couple of decades and that recent research both helps understand why they have worked so well and provides new insight into issues that need to be considered to ensure excellent long-term liner performance of composite liners — especially for applications where the liner temperature can exceed about 35 °C.
... Various situations were tested in the past to evaluate the effect of a smooth GM in contact with the GCL [5][6][7]. It has been verified that under steady-state conditions, the most significant fraction of the flow takes place along the interface between the GM and the cover geotextile of the GCL, through the cover geotextile, and along gaps between the cover geotextile of the GCL and the bentonite [5]. ...
... A less important amount of fluid percolates through the bentonite and below the GCL. The influence of the hydraulic head, pre-hydration of the GCL, and confining stress on the GM-GCL interface transmissivity has also been investigated [6,7]. The results obtained by those authors showed that it is difficult to establish general trends expressing the influence of pre-hydration, confining stress, and hydraulic head on the interface transmissivity. ...
... Transmissivity tests are carried out in an apparatus specially designed to measure the flow rate in a composite liner, as shown in Fig. 2. As previously described in the literature [6][7][8][9][10][11][12], it consists of a Plexiglas cell basically composed by four parts: (i) a bottom plate which supports the soil and applies the confining stress; (ii) a 200-mm-inside-diameter base cylinder, 80 mm high, to accommodate the compacted base soil and the mineral part of the multicomponent GCL specimen; (iii) a top coarse granular drainage layer; and (iv) an upper cylinder that accommodates the granular layer. To assemble the test, Note: K CCL , hydraulic conductivity of the soil composing the CCL; PI, plasticity index; x L , liquid limit; ...
Three different multicomponent geosynthetic clay liners (GCLs) from different manufacturers are tested in a transmissivity cell with a new testing procedure to quantify the flow rate and the interface transmissivity between the coating or attached film presenting a hole and the upper geotextile of the GCL. The testing device was previously used in studies aiming to evaluate the interface transmissivity between a damaged eomembrane (GM) and a regular GCL. Different results are obtained regarding the evolution
with the time of the flow rate ranging from 1.73� 10-m3/s to 2.18� 10-�10 m3/s at steady state, which is on average in the range of flow rate results obtained with a GM–GCL composite liner. Additional tests performed
by adding a GM on top give lower values of flow rates. This shows the importance of the film or coating rigidity for decreasing flow rate and insuring a better quality contact at the interface.
... Finalement on présente les résultats obtenus en termes de débit de fuite et de transmissivité d'interface obtenus pour une étanchéité composite contenant une GM-B et un GSB calcique. Le travail effectué durant les années précédentes (Brown et al., 1987 ; Harpur et al., 1993; Touze-Foltz, 2002 ; Touze-Foltz et al., 2002 ; Cartaud et Touze-Foltz, 2004 ; Barroso et al., 2006 Barroso et al., , 2008 Barroso et al., , 2010 Mendes et al., 2010) en ce qui concerne le comportement des étanchéités composites contenant un GSB et une GM endommagée en PEHD était concentré sur la détermination du débit de fuite et de la transmissivité d'interface dans l'interface séparant la GM et le géotextile supérieur du GSB. Le débit traversant le défaut dans la GM dépend, comme indiqué par Brown et al. (1987), de la qualité de contact entre la GM et le sol sous-jacent. ...
... Plusieurs situations ont été testées dans le passé dans le but d'évaluer le flux traversant une étanchéité composite formée d'une GM en contact avec un GSB (Harpur et al., 1993 ; Touze-Foltz, 2002 ; TouzeFoltz et al., 2002 ; Cartaud et Touze-Foltz, 2004 ; Barroso et al., 2006 Barroso et al., , 2008 Barroso et al., , 2010 Mendes et al., 2010). Harpur et al. (1993) ont vérifié qu'en régime permanent, la part la plus importante du liquide traversant la GM prend place le long de l'interface, à travers le géotextile supérieur du GSB et le long des vides existants entre le géotextile supérieur du GSB et la bentonite. ...
... Harpur et al. (1993) ont vérifié qu'en régime permanent, la part la plus importante du liquide traversant la GM prend place le long de l'interface, à travers le géotextile supérieur du GSB et le long des vides existants entre le géotextile supérieur du GSB et la bentonite. Barroso et al. (2006 Barroso et al. ( , 2010) ont examiné l'influence de la charge hydraulique, de la pré-hydratation initiale du GSB et de la contrainte de confinement appliquée sur l'étanchéité composite. Les résultats ont montré qu'il semble difficile d'établir des règles générales exprimant l'influence de ces paramètres sur la transmissivité d'interface. ...
Some studies were performed in the past years regarding the behaviour of geosynthetic
clay liners (GCLs) as part of a composite liner composed by a GCL located under a high density
polyethylene (HDPE) geomembrane (GM) exhibiting a hole. In this case, the contact between the GM
and the GCL was quantified in terms of flow rate and interface transmissivity. However one could
imagine that the use of other GMs, like bituminous geomembranes (B-GMs) associated to a GCL, could
be adapted for hydraulic applications. A quantification of flow rates was thus performed through
laboratory tests for the case of a damaged B-GM located on top of a GCL. This corresponds to an
alternative design for a canal projected in France at the moment
... Finally, the liquid migrates into and through the underlying medium ( Figure 2). Various situations were tested to evaluate the flow through a GMB in contact with a GCL (Harpur et al., 1993;Barroso et al., 2006Barroso et al., , 2010. Harpur et al. (1993) verified that, under steady-state conditions, the most significant fraction of the flow occurs along the interface between the GMB and the cover geotextile of the GCL, through the cover geotextile, and along gaps between the cover geotextile of the GCL and the bentonite. ...
... Small scale tests were carried out using two different apparatus in order to measure axisymmetric flow rate through composite liners. The first apparatus, shown in Figure 3 was used by Barroso et al. (2006Barroso et al. ( , 2008Barroso et al. ( , 2010, Bannour et al. (2013a, b), Mendes et al. (2010) and Touze-Foltz (2002). Flow rates were experimentally measured from which interface transmissivity have been calculated using the analytical solution for axisymmetric defect developed by Touze Foltz et al. (1999). ...
The equivalence of composite liners involving a geomembrane (GMB) and a geosynthetic clay liner (GCL) to regulatory composite liners with a GMB and a compacted clay liner (CCL) can offer greater environmental protection to the underlying aquifer. It is suggested that GCLs and GMBs can play a very beneficial role in providing environmental protection even though GCLs are altered by their environment due to cation exchange and wet-dry cycles or there are defects in the GMB. The performance of GMB-GCL composite liners is accessed in terms of diffusion of contaminants and in terms of advective transfer due to the presence of defects in GMBs. Experimental, numerical and empirical quantification of advective transfers are examined through single GMBs and GCLs and are compared to GMB-CCL composite liners included in the case of aged GCLs.
... .......40 Figura 3.6 -Relação entre a permeabilidade intrínseca do GCL e sua umidade volumétrica (Bouazza & Vangpaisal, 2003) Figura 3.7 -Evolução da vazão de gás em função do tempo para vários diferenciais de pressão de gás: efeito da sobrecarga na pré-hidratação (Bouazza & Vangpaisal, 2003)..........41 Figura 3.8 -Amostras de GCL costurado hidratados (a) com sobrecarga (b) sem sobrecarga Figura 3.14 -Cinética de queda de pressão do gás azoto ao longo do tempo: amostra de GCL com w = 99,7% (Pitanga, 2007) Figura 3.24 -Equipamento em escala intermediária para medida de vazão através de barreira composta devido a um dano na GM (Barroso, 2005;Barroso et al., 2006). ...............73 Figura 3.25 -Ensaio em grande escala para medida de vazão através de barreira composta devido a um dano na GM (Barroso, 2005;Barroso et al., 2006) Figura 3.29 -Evolução da vazão em função do tempo para diferentes pressões confinantes (Bergamini et al., 2009;Barroso et al., 2010) Les items 6.1 à 6.4 présentent les résultats des essais obtenus avec une étude de l'influence de différents facteurs sur la perméabilité aux gaz des GCLs. L'item 6.5 présente la conclusion de cette étude de la Partie II. ...
... Este item apresenta a descrição das pesquisas de laboratório desenvolvidas nesse sentido. Estornell & Daniel (1992) Figura 3.29 -Evolução da vazão em função do tempo para diferentes pressões confinantes (Bergamini et al., 2009;Barroso et al., 2010). Les bases pour la compréhension de la migration de gaz au travers des milieux poreux sont présentées dans l'item 3.1 avec les équations concernant les transferts diffusifs et advectifs. ...
Geosynthetic Clay Liners (GCLs) are synthetic materials composed by a core of calcium or sodium bentonite, either in powder or granular, bonded to one or more geosynthetic layers (geotextile or geomembrane, in general). These layers are usually bonded by an adhesive, needle-punching, stitch-bonding or sewing. When hydrated and confined, they fulfil functions of liquid or gas barrier with their hydraulic performance depending in most cases on the hydraulic conductivity of the bentonite. Thanks to their low permeability to water and gases, GCLs are often used in municipal solid waste landfill applications, combined to compacted clay liners (CCL) or with geomembranes (GM) as part of both bottom and cover liners. Previous studies were conducted to investigate the most important factors that influence the gas/liquid flow rate through GCLs or composite liners. Although the nature of bentonite is so important in the permeability of the GCLs there is a lack of data in the literature regarding the influence of the nature of the bentonite on the gas flow through GCLs and liquid flow through composite liners involving GCLs. That is what this thesis aims at clarifying. Furthermore, in conjunction with the nature of the bentonite, the impact of the manufacturing process of the GCL on the flow rate and transmissivity at GM-GCL interfaces was also discussed. Two studies were performed: (i) investigation of the GCL permeability to gas simulating the covering conditions of municipal solid waste landfill; (ii) investigation of liquid transfer through composite liners GM-GCL-CCL due to a defect in the geomembrane, simulating typical conditions of bottom liners in landfills. In the first study, an apparatus recently proposed, based on the falling pressure method, was used in tests to verify the GCL permeability to gas. Three stitch bonded GCLs from the same manufacturer differing by the bentonite nature (natural sodium, natural calcium and activated calcium) were tested. The results showed that the gravimetric water content of the GCL necessary to attain a certain permeability value depends on the bentonite nature, which was not observed in terms of volumetric water content. However, other factors showed to be more important than the nature of bentonite in the GCL permeability to gas: the desiccation due to the gas flow can increase significantly the permeability, which compromise the GCL performance as a gas barrier. The second study focused in investigating the influence of the GCL characteristics in the liquid flow through a composite liner under bottom liners solicitations. Four types of GCLs with two different bonding processes (stitch-bonded or needle-punched) and different bentonites (natural sodium or natural calcium) were tested. The results obtained showed no significant differences among flow rate versus time in most of the tests performed, especially after steady-state conditions of flow having been reached. An analytical solution was employed to estimate the transmissivity of the GM-GCL interfaces. This solution also allowed predictions of flow rates and radius of wetted areas for typical configurations of composite liners in the field. The results obtained showed little influence of the nature of the bentonite and the predominance of influence of the presence of preferential flow paths between the geomembrane and the GCL surface on the transmissivity of GM-GCL interfaces and flow rates through composite liners.
... .......40 Figura 3.6 -Relação entre a permeabilidade intrínseca do GCL e sua umidade volumétrica (Bouazza & Vangpaisal, 2003) Figura 3.7 -Evolução da vazão de gás em função do tempo para vários diferenciais de pressão de gás: efeito da sobrecarga na pré-hidratação (Bouazza & Vangpaisal, 2003)..........41 Figura 3.8 -Amostras de GCL costurado hidratados (a) com sobrecarga (b) sem sobrecarga Figura 3.14 -Cinética de queda de pressão do gás azoto ao longo do tempo: amostra de GCL com w = 99,7% (Pitanga, 2007) Figura 3.24 -Equipamento em escala intermediária para medida de vazão através de barreira composta devido a um dano na GM (Barroso, 2005;Barroso et al., 2006). ...............73 Figura 3.25 -Ensaio em grande escala para medida de vazão através de barreira composta devido a um dano na GM (Barroso, 2005;Barroso et al., 2006) Figura 3.29 -Evolução da vazão em função do tempo para diferentes pressões confinantes (Bergamini et al., 2009;Barroso et al., 2010) Les items 6.1 à 6.4 présentent les résultats des essais obtenus avec une étude de l'influence de différents facteurs sur la perméabilité aux gaz des GCLs. L'item 6.5 présente la conclusion de cette étude de la Partie II. ...
... Este item apresenta a descrição das pesquisas de laboratório desenvolvidas nesse sentido. Estornell & Daniel (1992) Figura 3.29 -Evolução da vazão em função do tempo para diferentes pressões confinantes (Bergamini et al., 2009;Barroso et al., 2010). Les bases pour la compréhension de la migration de gaz au travers des milieux poreux sont présentées dans l'item 3.1 avec les équations concernant les transferts diffusifs et advectifs. ...
... In China, the Chinese Ministry of Construction also prescribed the GM/GCL/CCL triple-layer composite liner as one of the liner systems for MSW landfills [6]. In recent years, researchers have investigated the triple-layer composite liner comprising GM/GCL/CCL or GM/GCL/AL from various perspectives [1,2,5,7,11,14,20,23,34,46,50]. Considering the common usage of the triple-layer composite liner, analytical solutions for contaminant diffusion through such liners could be useful for design and analysis. ...
This paper presents analytical solutions for predicting one-dimensional diffusion of an organic contaminant through a triple-layer composite liner system comprising a geomembrane (GM), a geosynthetic clay liner (GCL), and a compacted clay liner (CCL). We consider two different bottom boundary conditions, i.e., fixed-concentration bottom boundary and semi-infinite bottom boundary, for which the methods of separation of variables and Laplace transform, respectively, are used to obtain the analytical solutions. The proposed analytical solutions are then verified against the CST3 numerical model and an analytical solution available in the literature. Using the verified analytical solutions, a series of parametric studies is conducted to investigate the effect of several relevant parameters on contaminant transport through the GM/GCL/CCL liner system. The results indicate that the CCL thickness, the CCL distribution coefficient, and the effective diffusion coefficient of CCL have significant impact on contaminant diffusion in the GM/GCL/CCL liner system, whereas the effective diffusion coefficient of the GCL, the diffusion coefficient of the GM, and the partition coefficient of the GM have negligible effect on contaminant diffusion in the GM/GCL/CCL liner system. The analytical solutions presented herein can be used to aid the design of a triple-layer composite liner system and the verification of other numerical models.
... The value of θ away from the wrinkle is also expected to be low. For example, for another GCL with a nonwoven cover geotextile, Rowe and Abdelatty (2012) reported θ ¼ 2.2 × 10 −11 m 2 =s under 100 kPa of confining stress, while Barroso et al. (2010) reported θ ¼ 7.8 × 10 −12 m 2 =s under 200 kPa. Thus for a very low k and θ, away from the wrinkle, any flow occurring other than through the section of GCL immediately beneath the wrinkle is neglected. ...
The hydraulic performance of geosynthetic clay liner (GCL) overlapped seams relying on hydration of panel bentonite through a melted groove in one of its geotextiles to seal the overlap is reported for the situation where the seam is below a wrinkle in an overlying geomembrane. The amount of hydrated bentonite extruded through the groove at the seam depended on whether or not the groove melt was continuous. Flow along a seam having complete groove melt with well-hydrated bentonite was 2-3 times higher than that through a single panel of GCL below a wrinkle, but two orders of magnitude lower than that through a seam with incomplete groove melt. The effect of heat tacking on the hydraulic performance of an overlapped seam is examined. The method of heat tacking, the width of the heat-tacked zone, and its positioning at the seam were found to impact seam flow.
... Contact between the GM and the GCL was quantified in terms of the flow rate through the composite liner and in terms of interface transmissivity. Various situations were tested to evaluate the flow through a smooth GM in contact with a GCL (Harpur et al., 1993; Barroso et al., 2006b Barroso et al., , 2010). Harpur et al. (1993) verified that, under steady-state conditions, the most significant fraction of the flow occurs along the interface between the GM and the cover geotextile of the GCL, through the cover geotextile, and along gaps between the cover geotextile of the GCL and the bentonite. ...
This paper, which is based on an Invited Lecture for the 7th International Conference on Environmental Geotechnics, gives an updated overview of the properties of transfer of geosynthetic liner materials used in environmental applications. To begin, the water-retention curves of geosynthetic clay liners (GCLs) are discussed, with the focus being on the high temperatures that can be encountered and the concomitant risk of desiccation. Next, an overview is given of quantifying advective transfer through intact geomembranes (virgin or after exposure on site) and through multicomponent GCLs. Experimental quantification of advective transfer through composite liners is also addressed, whereby geomembranes or the film or coating of a multicomponent GCL is damaged. Finally, based on a literature review including the most recent data, the discussion turns to the diffusion of organic and inorganic species through virgin and aged geomembranes and GCLs. The synopsis of the most recent data presented here in terms of elementary transfer mechanisms, either advective or diffusive, should contribute to improving the quantification of transfer through barrier systems. These four topics were selected as they correspond to the fields of expertise of the co-authors in which they have been publishing in the past 20 years.
... In these applications, the GCL serves to minimise advective transport of fluids through any holes in the geomembrane (Rowe 1998;Touze-Foltz et al. 2001Touze-Foltz 2002;Touze-Foltz 2003, 2005;Touze-Foltz andGiroud 2003, 2005;Cartaud et al. 2005aCartaud et al. , 2005bCartaud et al. , 2005cIryo and Rowe 2005;Rowe 2005; Barroso et al. 2006;Bouazza and Vangpaisal 2006;Touze-Foltz and Barroso 2006;El-Zein and Rowe 2008;Bouazza et al. 2008, Saidi et al. 2008Mendes et al. 2011b). However, the long-term effectiveness of the composite liner action will depend on (a) the presence of holes and tensile strains (which can give rise to future holes) in the geomembrane, especially in wrinkles in the geomembrane (Rowe 1998(Rowe , 2005Take et al. 2007;Thusyanthan et al. 2007;Gudina 2008a, 2008b) (b) the transmissivity of the geomembrane/GCL interface (Harpur et al. 1993;Rowe 1998;; Barroso et al. 2008Barroso et al. , 2010Mendes et al. 2011a) (c) the hydraulic conductivity of the GCL (Rowe 1998; the question arises as to whether this will be achieved in the long term, especially in light of the potential for high temperatures at the landfill base. ...
A fully coupled model is used to simulate the results of large-scale laboratory tests that investigated the non-isothermal behaviour of geosynthetic clay liners in landfill basal liner applications. Results of numerical simulations of the laboratory tests in terms of water content, capillary pressure, temperature and stress distributions are presented, and encouraging agreement between the numerical and experimental results is achieved. Under the conditions examined, a 258C/m temperature gradient led to the development of tensile stresses within the GCL, increasing the resultant likelihood of cracking. A Poisson's ratio of 0.25 resulted in predicted horizontal tensile stresses supporting qualitative observation of desiccation cracking in the GCLs. One important implication of the work reported herein is that elevated temperatures need not occur for extended periods to create the risk of desiccation.
... There is now a reasonable amount of data regarding the transmissivity of geomembrane-GCL interfaces (e.g., Harpur et al. 1993; Barroso et al. 2008Barroso et al. , 2010Mendes et al. 2010aMendes et al. , 2010b. Using available data for typical leachate heads, liner hydraulic conductivity, liner thickness, and interface transmissivity, Rowe (2005) demonstrated that the observed leakage through primary liners in double-lined landfills (Bonaparte et al. 2002) was considerably greater than would be expected for the typical number of holes in geomembranes if the geomembrane were in intimate contact with the underlying clay liner. ...
The variation in length of the longest hydraulic features (connected wrinkles) formed in an exposed black high-density polyethylene (HDPE) geomembrane liner observed at different times of the day and in different seasons over multiple years is presented for both a 3% base slope and 3H:1V side slope at the Queen’s University Experimental Liner Test Site (latitude of 44°34′N and longitude 76°39′W). The longest wrinkle observed on the 0.15 ha base was about 1500 m. The longest wrinkle observed on the 0.17 ha slope was about 2000 m. The length of connected wrinkles is shown to be primarily related to solar radiation, although the soil and ambient temperature played a role in maintaining wrinkles in the afternoon as solar radiation decreased. Wrinkles of less than 20 m connected length were observed for geomembrane surface temperatures of less than 30 °C and solar radiation of less than 600 W/m². Wrinkles exceeding 500 m in connected length were observed for geomembrane temperatures between about 30 and 62 °C and solar radiation between 600 and 1100 W/m². The vast majority (about 85%) of wrinkle heights were between 0.04 and 0.08 m with the average wrinkle height being 0.06 m and a maximum wrinkle height of about 0.18 m. The manually measured wrinkle widths around noon (when there was the greatest number of wrinkles) ranged between about 0.20 and 0.43 m, but most of the wrinkles were between 0.23 and 0.36 m with a mean of 0.29 m (standard deviation 0.05 m). The data from this study suggest that a reasonable estimate of mean wrinkle width would be about 0.2 to 0.3 m. The size of the area constraining the geomembrane is shown to affect the connected wrinkle length. Calculations of leakage for the wrinkle lengths and widths observed are reported to be consistent with what has been reported for landfills in North America.
This study aimed to assess the impact of soil lithology in the watertightness of aerated lagoon systems in oil factory company in two councils (Dibombari and Edea 1st) in the Littoral region of Cameroon. Primary data were obtained through sampling and analysing wastewater in the rst basin, soils at various depths (3 m, 7 m, 15 m and 21 m) and groundwater after piezometers' construction. Data processing involved several steps. Firstly, wastewater parameters were compared to soil parameters at three meters. Secondly, the evolution of soil parameters was analysed for each site by calculating pollutant reductions based on lithological sections. Finally, groundwater parameters from both sites were compared. The results showed that the lagoons systems with geotextile membrane, although quite effective, have shortcomings concerning in particular total nitrogen and phosphates. Due to its lithology, the Dibombari site provided better watertightness (nal reductions ranging from 99.84% for total organic matter to 27.20% for sulphates) than that of Edéa (nal reductions ranging from 97.25% for total nitrogen to 36.40% for sulphates). Laterites, clayed sands, and clays were the soil types with purifying and ltering qualities associated particularly to these reductions of nitrates and phosphates concentrations. Comparing the piezometers' groundwater highlighted the superior water quality at the Dibombari site, whose characteristics are closer to natural raw water than those at the Edéa site. Combining these soil types with geotextile membranes during the construction of local lagoon basins could enhance water retention, directly protecting groundwater and indirectly offering opportunities for optimizing waterproofing technology.
L’étanchéité composite géomembrane (GM)-géosynthétique bentonitique (GSB) mise en place dans les barrières de fond d’installations de stockage de déchets non dangereux (ISDnD) peut être sujette à des transferts advectifs liés à l’existence de défauts dans la GM. Les lixiviats peuvent percoler dans le GSB, pénétrer dans le sol et les nappes phréatiques sous-jacentes ce qui peut nuire à l’environnement. Il est donc important de comprendre les mécanismes de transferts dans les étanchéités composites GM-GSB et de les quantifier afin de connaitre, maitriser et minimiser l’impact des transferts advectifs et des flux entrant à travers la barrière vers l’environnement. Cependant, l’inaccessibilité de la GM rend difficile l’estimation réelle des fuites à travers l’étanchéité composite. La présente thèse évalue via une démarche expérimentale et numérique les transferts advectifs à travers les étanchéités composites et contribue à améliorer la compréhension des mécanismes de transfert en fonction des sollicitations extérieures. Le but est de bien cerner la problématique des transferts advectifs à travers les étanchéités composites GM-GSB, combler le manque de données des précédentes études et mettre en évidence les principaux paramètres à prendre en compte (contrainte de confinement, hétérogénéité du GSB, qualité de contact à l’interface GM-GSB, altération chimique et physique du GSB durant sa durée de service sur site). Leur influence sur l'étanchéité de l'ensemble et sur l’évolution des caractéristiques des matériaux utilisés est étudiée.
The available evidence suggests that both geosynthetic clay liners (GCLs) and composite liners with a geomembrane (GMB) over a clay liner have performed extremely well at controlling leakage in field applications for a couple of decades. However, there have also been some problems reported and recent research has allowed us to have a much better understanding of the key design and construction factors affecting good and poor performance. This paper examines some of these issues including factors affecting GCL performance such as the water retention curve of GCLs, subgrade grain size and initial water content, GCL water content and normal stress on the GCL, the effect of daily thermal cycles on hydration, GCL panel shrinkage and cation exchange. Factors affecting composite liner performance examined include the potential for desiccation of the clay liner under a sustained thermal gradient, GMB/GCL interface transmissivity, wrinkles in the GMB when the ballast layer is placed over the composite liner and the potential interaction between wrinkles and GCL panel overlaps. Recent insights regarding leakage through composite liners are discussed. Although a number of potential issues with liner performance are discussed, it is concluded that all can be addressed by appropriate design, material selection, construction and operations.
A GCL may desiccate as a result of one or more wet–dry cycle. This may occur because the GCL is in an exposed composite liner (i.e., the mechanisms giving rise to shrinkage discussed earlier), the GCL is in a cover liner without adequate cover soil to protect it from significant wet–dry cycles due to climatic cycles or because it is in a composite bottom liner that initially hydrates and is then dried by the thermal gradient generated by hot waste (e.g., municipal solid waste where there is leachate recirculation or disposal of combustion ash). When it desiccates, the GCL k value will be high but, provided that there is not too much cation exchange, it can quickly reduce again to low values (Southen and Rowe, 2005) because of the ability of the sodium bentonite to swell and self-heal on re-wetting (i.e., when it comes into contact with the fluid that is to be contained). However, as indicated by some of the cases cited in the previous section, when desiccation is combined with cation exchange the self-healing capacity is reduced or lost, with the magnitude of the effect depending on (a) the amount of cation exchange, (b) the extent of the cracking and the size of the desiccation cracks and (c) the stress on the GCL (higher stress increases the ability of the GCL to self-heal, other things being equal). The ability to rehydrate to a low k may also be reduced by the chemical composition of the permeant (Petrov and Rowe, 1997) even if there was little initial cation exchange.
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.
Geosynthetics play a very important role in modern barrier systems designed to control contaminant migration from waste disposal sites. This paper discusses the effect of temperature, the importance of consideration of clogging of filters and drainage layers, the service life of compacted clay liners beneath geomembranes, the hydraulic conductivity and service life of geosynthetic clay liners (GCLs), diffusion through GCLs, the service life of geomembranes and composite liner systems in the design of these systems. It discusses why any evaluation of equivalence of liner systems should go beyond simple hydraulic equivalency and should consider issues such as diffusive transport and service life. Finally, it highlights the importance of considering conventional stability issues in addition to contaminant transport issues in the design and construction of landfill barrier systems.
A general framework for calculating the rate of liquid flow through a composite liner (geomembrane plus soil liner) with holes is presented. Solutions given for a circular hole and a damaged wrinkle can be used for interpreting data from laboratory tests, modelling expected field conditions, and interpreting field leakage data. A number of existing solutions arise from the general solution as special cases. Finally, the paper is extended to consider the potential interaction between damaged wrinkles, and it is theoretically shown that while this may be an important issue for composite liners incorporating a compacted clay liner, it is far less likely to be significant for those incorporating a geosynthetic clay liner.
This paper presents empirical equations for the evaluation of advective flow rates through composite liners (i.e. liners comprising a geomembrane and a low-permeability soil layer). The advective flow is due to defects in the geomembrane and depends on contact conditions between the geomembrane and the soil layer. Three types of defect (circular defects, defects of infinite length, and damaged wrinkles) and three types of contact conditions (excellent, good, and poor) are considered. The methodology for developing the empirical equations consists in selecting a mathematical expression for the empirical equations and selecting values for the unknowns of the empirical equations such that flow rates calculated using the empirical equations are as close as possible to flow rates rigorously calculated using existing analytical solutions. This was achieved by conducting numerical calculations for more than 1,10,000 cases defined by a wide range of values of the parameters (contact conditions, defect type and size, soil layer thickness and hydraulic conductivity, and hydraulic head). As the empirical. equations are much simpler than the analytical solutions, they provide design engineers with a practical tool for evaluating flow rates through composite liners.
The combined use of several geological, geochemical and geophysical observations during six years enabled the detection of a very faint halo of chemical contamination induced by the operation of a young waste disposal facility in Northern Portugal. The halo does not classify as pollution by any standards, but is observed to be intensifying and thus signals a potential hazardous situation in future years. The approach used shows that a comprehensive and diverse monitoring programme, although relatively inexpensive and easy to carry out, may detect concealed leaks long before any environmental concern is justified, and thus may help avert future complex remediation needs caused by the uncontrolled growth of undetected underground pollution plumes.
Composite liners comprising a geomembrane (GM) with a circular hole, a geosynthetic clay liner (GCL) and a compacted clay liner were studied in tests conducted at three scales to measure the flow rates at the interface between the GM and the GCL and in the composite liners. The tests conducted aimed at studying the influence of the prehydration of the GCLs, the influence of the confining stress, and the influence of the hydraulic head on flow rates through composite liners due to defects in the GM. Another goal of these tests was to check the feasibility of an extrapolation of results obtained from small-scale tests to field conditions. The results indicate that the prehydration affected flow rate in a different way according to the confining stress applied and the GCL used. These also indicate that the flow rate decreases with the increase in confining stress and that this effect is higher for prehydrated GCLs than for non-prehydrated GCLs. These results show as well that the flow rate increases when the hydraulic head increases. Finally, small-scale tests overestimate the flow as compared to intermediate and large-scale tests and thus flow obtained in small-scale tests represent an upper bound of flow that would be obtained in field conditions.
Composite liners are used to limit the contamination migration from landfills. Their successful performance is closely related with the geomembrane as it provides the primary barrier to diffusive and advective transport of contaminants. Critical issues on the performance of the geomembranes are the seams between geomembrane panels and the inevitable defects resulting, for instance, from inadequate installation activities. In landfills, where high density polyethylene geomembranes are usually used, seams are typically made by the thermal-hot dual wedge method. A literature review on quality control of the seams showed that, in situ, fluid-tightness of seams is evaluated in qualitative terms (pass/failure criteria), despite their importance to ensure appropriate performance of the geomembranes as barriers. In addition, a synthesis of studies on geomembrane defects indicated that defects varying in density from 0.7 to 15.3 per hectare can be found in landfills. Defects represent preferential flow paths for leachate. Various authors have developed analytical solutions and empirical equations for predicting the flow rate through composite liners due to defects in the geomembrane. The validity of these methods for composite liners comprising a geomembrane over a geosynthetic clay liner (GCL) over a compacted clay liner (CCL) has never been studied from an experimental point of view. To address the problem of fluid migration through the geomembrane seams, an attempt is made to provide a test method, herein termed as "gas permeation pouch test", for assessing the quality of the thermal-hot dual wedge seams. This test consists of pressurising the air channel formed by the double seam with a gas to a specific pressure and, then, measuring the decrease in pressure over time. From the pressure decrease, both the gas permeation coefficients, in steady state conditions, and the time constant, in unsteady state conditions, can be estimated. Experiments were carried out both in laboratory and in field conditions to study the suitability of this test to assess the quality of the seams in situ. The results obtained suggest that it is possible to assess the quality of the geomembrane seams from a non-destructive test conducted in situ by determining the time constant. To address the problem of fluid migration through geomembrane defects, composite liners comprising a geomembrane with a circular hole over a GCL over a CCL were simulated in tests at three scales. Flow rates at the interface between the geomembrane and the GCL were measured. Correspondent interface transmissivity was estimated based on final flow rates and observation of the wetted area. A parametric study was performed to evaluate the influence of the prehydration of the GCL, the hydraulic head on top of the liner and the confining stress over the liner system, on the flow rate through composite liners due to defects in the geomembrane, as well as to check the feasibility of an extrapolation of the results obtained on small-scale tests to field conditions. It was found that the transmissivity does not seem to be affected by the prehydration of the GCLs when low confining stresses were used. It also does not seem to be influenced by the increase in confining stress when non-prehydrated GCLs are used. Finally, the transmissivity does not seem to be significantly affected by the increase in hydraulic head. The results also suggest that predictions on flow rates though composite liners due to defects in the geomembrane, which are based on transmissivity values obtained in small scale tests, are conservative. Lastly, based on the transmissivities obtained in this study, empirical equations for predicting the flow rate through composite liners consisting of a geomembrane over a GCL over a CCL are proposed. Flow rates calculated using these equations are in better agreement with the flow rates measured experimentally than the empirical equations reported in literature. The new empirical equations provide design engineers with simple and accurate tools for calculating the flow rates through the above mentioned type of composite liners.
The hydraulic conductivity of three 2.9 m2 (32 sq ft) geosynthetic clay liners (GCLs) was measured. Tests were performed on individual sheets of the GCLs, on overlapped pieces of GCLs, and on composite liners consisting of a punctured geomembrane overlying a GCL. Hydraulic conductivities of two of the GCLs were in the range of 10-10 to 10-8 cm/s. No flow was measured through the third GCL, but the conductivity was obviously very low (≪ 10-7 cm/s). The hydraulic conductivities of overlapped GCLs were about the same as those of the control samples with no overlap; an effective hydraulic seal developed along the overlaps in all of the materials tested. Performance of the punctured geomembrane-GCL composites varied - performance was best when the punctured geomembrane was placed directly against bentonite and no geotextile separated the punctured geomembrane from the bentonite. For those GCLs with geotextiles on both sides, problems with migration of bentonite into the underlying drainage layer were encountered when inadequate filtration was provided. However, with a suitable filtration layer separating the drainage layer from the GCL, problems with migration of bentonite were eliminated.
This technical note presents empirical equations for the evaluation of the rate of advective flow through composite liners, i.e. liners comprising a geomembrane and a low-permeability soil layer. The advective flow considered is due to large circular defects in the geomembrane. The flow rate depends on contact conditions between the geomembrane and the soil layer. Three types of contact conditions ( excellent, good, and poor) are considered. The methodology for developing the empirical equations is identical to the one proposed by Touze-Foltz and Giroud for small circular defects. The methodology consists in determining values for the unknowns of the empirical equations such that flow rates calculated using the empirical equations are as close as possible to flow rates rigorously calculated using existing analytical solutions. This was achieved by conducting numerical calculations for more than 38,000 cases defined by a wide range of values of the parameters ( contact conditions, soil layer thickness and hydraulic conductivity, and hydraulic head).
This paper presents equations for the evaluation of advective flow rates though composite liners involving GCLs. Advective flow is due to the existence of defects in the geomembrane, and depends on the contact condition between the geomembrane and the GCL. In this paper the geomembrane - geosynthetic clay liner contact condition is quantitatively defined, based on experimental data. Accordingly, empirical equations are presented for circular defects having diameters in two different ranges: 2 to 20 mm and 100 to 600 mm. The validity of the empirical equation obtained for the smallest range of diameters is compared with experimental results and with an existing empirical equation. The empirical equations developed in this paper are then combined in a simple analytical solution, leading to semi-empirical equations that allow one to predict flow rates for narrow and wide defects, taking account of the flow that takes place at both ends of these defects of finite length. A parametric study shows, through a correlation factor, the importance of the flow at both ends of defects of finite length, mainly for narrow defects.
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