Documents disponibles écrits par cet auteur

Effect of GCL properties on shrinkage when subjected to wet-dry cycles / R. Kerry Rowe in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 11 (Novembre 2011) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 11 (Novembre 2011) . - pp. 1019-1027 Titre : Effect of GCL properties on shrinkage when subjected to wet-dry cycles Type de document : texte imprimé Auteurs : R. Kerry Rowe, Auteur ; L. E. Bostwick, Auteur ; W. A. Take, Auteur Année de publication : 2012 Article en page(s) : pp. 1019-1027 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : GCL  Shrinkage  Bentonite Résumé : The potential shrinkage of eight different geosynthetic clay liners (GCLs) subjected to wetting and drying cycles is examined. It is shown that the initial (e.g, off-the-roll) moisture content may affect the initial shrinkage but did not notably affect the final equilibrium shrinkage. For GCLs with granular bentonite and wetted to a moisture content of about 60% (or greater) in the hydration phase, the actual moisture content did not appear to affect the magnitude of the final equilibrium shrinkage. However, it did affect the rate of shrinkage. Specimens brought to about 100% moisture content in each cycle reached a constant shrinkage value much faster than those brought to about 60% in each wetting cycle. GCLs containing powdered bentonite generally shrank more than those containing granular bentonite. All of the powdered bentonite specimens continued a slow accumulation of strain with increasing cycles, even up to 75 cycles. The shrinkage of a needle-punched GCL with a thermally treated scrim-reinforced nonwoven carrier geotextile and granular bentonite was less than that for a needle-punched GCL with a simple nonwoven carrier and granular bentonite. For some products, there was considerable variability in GCL shrinkage for specimens from the same roll and tested under nominally identical conditions, whereas for other products, the variability was relatively small. The shrinkage strain required to cause the loss of a 150–300 mm panel overlap is shown to be able to be mobilized in about five wet-dry cycles in the experiments reported. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i11/p1019_s1?isAuthorized=no [article] Effect of GCL properties on shrinkage when subjected to wet-dry cycles [texte imprimé] / R. Kerry Rowe, Auteur ; L. E. Bostwick, Auteur ; W. A. Take, Auteur . - 2012 . - pp. 1019-1027. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 11 (Novembre 2011) . - pp. 1019-1027 Mots-clés : GCL  Shrinkage  Bentonite Résumé : The potential shrinkage of eight different geosynthetic clay liners (GCLs) subjected to wetting and drying cycles is examined. It is shown that the initial (e.g, off-the-roll) moisture content may affect the initial shrinkage but did not notably affect the final equilibrium shrinkage. For GCLs with granular bentonite and wetted to a moisture content of about 60% (or greater) in the hydration phase, the actual moisture content did not appear to affect the magnitude of the final equilibrium shrinkage. However, it did affect the rate of shrinkage. Specimens brought to about 100% moisture content in each cycle reached a constant shrinkage value much faster than those brought to about 60% in each wetting cycle. GCLs containing powdered bentonite generally shrank more than those containing granular bentonite. All of the powdered bentonite specimens continued a slow accumulation of strain with increasing cycles, even up to 75 cycles. The shrinkage of a needle-punched GCL with a thermally treated scrim-reinforced nonwoven carrier geotextile and granular bentonite was less than that for a needle-punched GCL with a simple nonwoven carrier and granular bentonite. For some products, there was considerable variability in GCL shrinkage for specimens from the same roll and tested under nominally identical conditions, whereas for other products, the variability was relatively small. The shrinkage strain required to cause the loss of a 150–300 mm panel overlap is shown to be able to be mobilized in about five wet-dry cycles in the experiments reported. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i11/p1019_s1?isAuthorized=no

Large-scale quantification of wrinkles in a smooth black HDPE geomembrane / M. J. Chappel in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 6 (Juin 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 6 (Juin 2012) . - pp. 671–679 Titre : Large-scale quantification of wrinkles in a smooth black HDPE geomembrane Type de document : texte imprimé Auteurs : M. J. Chappel, Auteur ; R. W. I. Brachman, Auteur ; W. A. Take, Auteur Année de publication : 2012 Article en page(s) : pp. 671–679 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Geomembranes  Lining  Landfills Résumé : Wrinkles are buckles or waves that develop from restrained thermal expansion when the geomembrane is left exposed to solar heating. Wrinkles can substantially reduce the effectiveness of the geomembrane as a hydraulic barrier if a hole is at or near a wrinkle, depending on the number, length, and width of wrinkles. Low altitude aerial photography and digital image analysis are used to quantify the nature and extent of wrinkles that developed over one hot and sunny day in a smooth, black, 1.5-mm-thick high-density polyethylene (HDPE) geomembrane over a 55 m by 140 m area. Wrinkles were found to significantly vary over the course of the day, increasing from the fewest wrinkles in the morning to a maximum just after noon before decreasing toward the late afternoon. For the specific conditions examined, wrinkles were found to occupy 3%, 21%, and 7% of the entire area surveyed at 8:45, 12:25, and 17:15, respectively. Connections between adjacent wrinkles were observed to create significant interconnected wrinkle features greater than 2,000 m long. The shortest maximum interconnected wrinkle feature of 80  m/ha was measured at 8:45 while the longest such feature was 6,600  m/ha at 13∶45. The observations and results provide data to support the approach that limiting the time of day when cover is placed on geomembrane can be effective at reducing the extent of wrinkling. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000643 [article] Large-scale quantification of wrinkles in a smooth black HDPE geomembrane [texte imprimé] / M. J. Chappel, Auteur ; R. W. I. Brachman, Auteur ; W. A. Take, Auteur . - 2012 . - pp. 671–679. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 6 (Juin 2012) . - pp. 671–679 Mots-clés : Geomembranes  Lining  Landfills Résumé : Wrinkles are buckles or waves that develop from restrained thermal expansion when the geomembrane is left exposed to solar heating. Wrinkles can substantially reduce the effectiveness of the geomembrane as a hydraulic barrier if a hole is at or near a wrinkle, depending on the number, length, and width of wrinkles. Low altitude aerial photography and digital image analysis are used to quantify the nature and extent of wrinkles that developed over one hot and sunny day in a smooth, black, 1.5-mm-thick high-density polyethylene (HDPE) geomembrane over a 55 m by 140 m area. Wrinkles were found to significantly vary over the course of the day, increasing from the fewest wrinkles in the morning to a maximum just after noon before decreasing toward the late afternoon. For the specific conditions examined, wrinkles were found to occupy 3%, 21%, and 7% of the entire area surveyed at 8:45, 12:25, and 17:15, respectively. Connections between adjacent wrinkles were observed to create significant interconnected wrinkle features greater than 2,000 m long. The shortest maximum interconnected wrinkle feature of 80  m/ha was measured at 8:45 while the longest such feature was 6,600  m/ha at 13∶45. The observations and results provide data to support the approach that limiting the time of day when cover is placed on geomembrane can be effective at reducing the extent of wrinkling. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000643

Seasonal ratcheting and softening in clay slopes, leading to first-time failure / W. A. Take in Géotechnique, Vol. 61 N° 9 (Septembre 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 9 (Septembre 2011) . - pp. 757-769 Titre : Seasonal ratcheting and softening in clay slopes, leading to first-time failure Type de document : texte imprimé Auteurs : W. A. Take, Auteur ; M. D. Bolton, Auteur Année de publication : 2011 Article en page(s) : pp. 757-769 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Centrifuge  modelling  Slopes  Clays  Failure Index. décimale : 551.4 Résumé : Centrifuge tests have been carried out on kaolin clay slopes subject to variations in surface rainfall and humidity corresponding, at model scale, to successive wet and dry seasons in the field. These model slopes have been instrumented with miniature high-capacity tensiometers, and the deformations of their cross-sections have been observed by digital photography and analysed by particle image velocimetry. Sequences of swelling and shrinkage have been seen to be potentially irreversible, leading to creep in the form of down-slope ratcheting, accompanied by progressive regional softening within the zone affected by the seasonal moisture movements. Ultimately, this regional softening has been seen to lead to slope failures, in which segments of soil have separated from the mass through the opening of tension cracks and the formation of a localised shear rupture. An analysis of the phase of episodic regional softening is presented here, based on a Spencer limit-equilibrium approach. These back-analyses illustrate that clay slopes which temporarily mobilise an average stress ratio in excess of the critical state stress ratio during any portion of a typical year may eventually be brought to a long-term failure under the action of seasonal variations of pore pressure. Conversely, it is hypothesised that clay slopes which can maintain their overall equilibrium without exceeding the critical state stress ratio may not experience progressive seasonal softening. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.125 [article] Seasonal ratcheting and softening in clay slopes, leading to first-time failure [texte imprimé] / W. A. Take, Auteur ; M. D. Bolton, Auteur . - 2011 . - pp. 757-769. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 9 (Septembre 2011) . - pp. 757-769 Mots-clés : Centrifuge  modelling  Slopes  Clays  Failure Index. décimale : 551.4 Résumé : Centrifuge tests have been carried out on kaolin clay slopes subject to variations in surface rainfall and humidity corresponding, at model scale, to successive wet and dry seasons in the field. These model slopes have been instrumented with miniature high-capacity tensiometers, and the deformations of their cross-sections have been observed by digital photography and analysed by particle image velocimetry. Sequences of swelling and shrinkage have been seen to be potentially irreversible, leading to creep in the form of down-slope ratcheting, accompanied by progressive regional softening within the zone affected by the seasonal moisture movements. Ultimately, this regional softening has been seen to lead to slope failures, in which segments of soil have separated from the mass through the opening of tension cracks and the formation of a localised shear rupture. An analysis of the phase of episodic regional softening is presented here, based on a Spencer limit-equilibrium approach. These back-analyses illustrate that clay slopes which temporarily mobilise an average stress ratio in excess of the critical state stress ratio during any portion of a typical year may eventually be brought to a long-term failure under the action of seasonal variations of pore pressure. Conversely, it is hypothesised that clay slopes which can maintain their overall equilibrium without exceeding the critical state stress ratio may not experience progressive seasonal softening. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.125

Thermal expansion and contraction of geomembrane liners subjected to solar exposure and backfilling / W. A. Take in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 11 (Novembre 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 11 (Novembre 2012) . - pp. 1387–1397 Titre : Thermal expansion and contraction of geomembrane liners subjected to solar exposure and backfilling Type de document : texte imprimé Auteurs : W. A. Take, Auteur ; E. Watson, Auteur ; R. W. I. Brachman, Auteur Année de publication : 2013 Article en page(s) : pp. 1387–1397 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Geomembranes  Lining  Landfills Résumé : Geomembranes (GMBs) are widely used as advective barriers in landfill liner systems. When exposed to the sun, GMBs exhibit a network of wrinkles as a result of thermal expansion. These wrinkles disrupt the intimate contact between the GMB and the underlying layer. If a hole is coincident with a GMB wrinkle then the space under the wrinkle has the potential to act as a preferential pathway for flow of contaminants. Thus, the size and shape of GMB wrinkles have implications for leakage rates through the composite liner system. However, wrinkles are only a concern if they persist after placement of backfill, which is currently a subject of debate. In this paper, wrinkles are induced in a 1.5-mm-thick, black high-density polyethylene strip GMB specimen overlying a geosynthetic clay liner using natural solar and laboratory energy sources. Particle image velocimetry techniques are employed to record cross-sectional wrinkle geometry during growth and subsequent backfilling. This cross-sectional geometry is found to follow a Gaussian shape in which the height increases with the temperature and the width remains relatively constant. The resulting relationships between the height and temperature permit an estimation of wrinkle height for a known coefficient of thermal expansion for the GMB and an estimate of wrinkle spacing. For the GMB material and conditions tested, the results of the backfilling experiments indicate that when covered with 230 mm of cool sand (21°C), wrinkles of initial height less than about 20 mm disappear completely, while larger wrinkles remain with a reduced height. Furthermore, wrinkles of 20 mm in height are observed to form with increases in GMB temperature of less than 5°C. With application to the field, these findings indicate that a GMB must be covered at or below its installation temperature to achieve a wrinkle-free installation. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000694 [article] Thermal expansion and contraction of geomembrane liners subjected to solar exposure and backfilling [texte imprimé] / W. A. Take, Auteur ; E. Watson, Auteur ; R. W. I. Brachman, Auteur . - 2013 . - pp. 1387–1397. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 11 (Novembre 2012) . - pp. 1387–1397 Mots-clés : Geomembranes  Lining  Landfills Résumé : Geomembranes (GMBs) are widely used as advective barriers in landfill liner systems. When exposed to the sun, GMBs exhibit a network of wrinkles as a result of thermal expansion. These wrinkles disrupt the intimate contact between the GMB and the underlying layer. If a hole is coincident with a GMB wrinkle then the space under the wrinkle has the potential to act as a preferential pathway for flow of contaminants. Thus, the size and shape of GMB wrinkles have implications for leakage rates through the composite liner system. However, wrinkles are only a concern if they persist after placement of backfill, which is currently a subject of debate. In this paper, wrinkles are induced in a 1.5-mm-thick, black high-density polyethylene strip GMB specimen overlying a geosynthetic clay liner using natural solar and laboratory energy sources. Particle image velocimetry techniques are employed to record cross-sectional wrinkle geometry during growth and subsequent backfilling. This cross-sectional geometry is found to follow a Gaussian shape in which the height increases with the temperature and the width remains relatively constant. The resulting relationships between the height and temperature permit an estimation of wrinkle height for a known coefficient of thermal expansion for the GMB and an estimate of wrinkle spacing. For the GMB material and conditions tested, the results of the backfilling experiments indicate that when covered with 230 mm of cool sand (21°C), wrinkles of initial height less than about 20 mm disappear completely, while larger wrinkles remain with a reduced height. Furthermore, wrinkles of 20 mm in height are observed to form with increases in GMB temperature of less than 5°C. With application to the field, these findings indicate that a GMB must be covered at or below its installation temperature to achieve a wrinkle-free installation. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000694