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On-sample water content measurement for a complete local monitoring in triaxial testing of unsaturated soils / J. A. Munoz-Castelblanco in Géotechnique, Vol. 62 N° 7 (Juillet 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 7 (Juillet 2012) . - pp. 595 –604 Titre : On-sample water content measurement for a complete local monitoring in triaxial testing of unsaturated soils Type de document : texte imprimé Auteurs : J. A. Munoz-Castelblanco, Auteur ; P. Delage, Auteur ; J. M. Pereira, Auteur Année de publication : 2012 Article en page(s) : pp. 595 –604 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Suction  Partial  saturation  Laboratory  equipment Résumé : To provide a complete local monitoring of the state of an unsaturated soil sample during triaxial testing, a local water content measurement device was adapted to a triaxial device comprising the measurement of local displacements (Hall effect transducers) and suction (high-capacity transducer). Water content was locally monitored by means of a resistivity probe. The water content/resistivity calibration curves of an intact, natural, unsaturated loess from northern France extracted by block sampling at two depths (1 and 3·3 m) were carefully determined, showing good accuracy and repeatability. The validity of two models giving the resistivity of unsaturated soils with respect to their water content was examined. The first triaxial tests carried out with this device in the range of in situ stresses gave satisfactory results, but with some effects of the applied cell stress on the water content measurements. Some preliminary behaviour characteristics of the natural unsaturated loess, a material rarely tested up to now in the literature, were evidenced. Also, the yield stresses appeared significantly higher than the in situ stresses, confirming the combined effect of partial saturation and bonding. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.129 [article] On-sample water content measurement for a complete local monitoring in triaxial testing of unsaturated soils [texte imprimé] / J. A. Munoz-Castelblanco, Auteur ; P. Delage, Auteur ; J. M. Pereira, Auteur . - 2012 . - pp. 595 –604. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 7 (Juillet 2012) . - pp. 595 –604 Mots-clés : Suction  Partial  saturation  Laboratory  equipment Résumé : To provide a complete local monitoring of the state of an unsaturated soil sample during triaxial testing, a local water content measurement device was adapted to a triaxial device comprising the measurement of local displacements (Hall effect transducers) and suction (high-capacity transducer). Water content was locally monitored by means of a resistivity probe. The water content/resistivity calibration curves of an intact, natural, unsaturated loess from northern France extracted by block sampling at two depths (1 and 3·3 m) were carefully determined, showing good accuracy and repeatability. The validity of two models giving the resistivity of unsaturated soils with respect to their water content was examined. The first triaxial tests carried out with this device in the range of in situ stresses gave satisfactory results, but with some effects of the applied cell stress on the water content measurements. Some preliminary behaviour characteristics of the natural unsaturated loess, a material rarely tested up to now in the literature, were evidenced. Also, the yield stresses appeared significantly higher than the in situ stresses, confirming the combined effect of partial saturation and bonding. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.129

The water retention properties of a natural unsaturated loess from northern France / J. A. Munoz-Castelblanco in Géotechnique, Vol. 62 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 2 (Fevrier 2012) . - pp. 95 –106 Titre : The water retention properties of a natural unsaturated loess from northern France Type de document : texte imprimé Auteurs : J. A. Munoz-Castelblanco, Auteur ; J. M. Pereira, Auteur ; P. Delage, Auteur Année de publication : 2012 Article en page(s) : pp. 95 –106 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Suction  Permeability  Laboratory  tests Résumé : The water retention properties of a natural loess from northern France were investigated on intact block samples that were excavated along a high-speed train line (TGV) that experienced stability problems during heavy rain episodes. Suction measurements were made by using the filter paper method and an in-house constructed high-capacity tensiometer (HCT) so as to determine the water retention curve of the loess. The results showed that an alternative approach using a previously wetted filter paper could fruitfully be used with suction values reasonably compatible with the HCT measurements. The water retention curve obtained exhibited a peculiar form, with no hysteresis observed around the natural water content (14·4%) and two hysteresis loops on both the wet and dry sides of the curve. It is hypothesised that this zone with no hysteresis corresponds to the natural variations of the water content under seasonal changes, providing a range of natural suction between 20 and 80 kPa, and it is suggested that this should be checked by in situ measurements. The loess microstructure was investigated by using scanning electron microscopy and mercury intrusion porosimetry. It appeared that the clay fraction (16%) was not uniformly distributed, with some areas composed of clean grains and a well-graded corresponding intergrain pore population. Conversely, the clay aggregations define a smaller-sized porosity. The calculation of a water retention curve derived from the pore size distribution curve showed that water retention is governed by capillarity in the largest pores between clean grains, whereas clay adsorption becomes dominant in the smallest pores, a zone where the microstructure is sensitive to change in water content. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.P.084 [article] The water retention properties of a natural unsaturated loess from northern France [texte imprimé] / J. A. Munoz-Castelblanco, Auteur ; J. M. Pereira, Auteur ; P. Delage, Auteur . - 2012 . - pp. 95 –106. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 2 (Fevrier 2012) . - pp. 95 –106 Mots-clés : Suction  Permeability  Laboratory  tests Résumé : The water retention properties of a natural loess from northern France were investigated on intact block samples that were excavated along a high-speed train line (TGV) that experienced stability problems during heavy rain episodes. Suction measurements were made by using the filter paper method and an in-house constructed high-capacity tensiometer (HCT) so as to determine the water retention curve of the loess. The results showed that an alternative approach using a previously wetted filter paper could fruitfully be used with suction values reasonably compatible with the HCT measurements. The water retention curve obtained exhibited a peculiar form, with no hysteresis observed around the natural water content (14·4%) and two hysteresis loops on both the wet and dry sides of the curve. It is hypothesised that this zone with no hysteresis corresponds to the natural variations of the water content under seasonal changes, providing a range of natural suction between 20 and 80 kPa, and it is suggested that this should be checked by in situ measurements. The loess microstructure was investigated by using scanning electron microscopy and mercury intrusion porosimetry. It appeared that the clay fraction (16%) was not uniformly distributed, with some areas composed of clean grains and a well-graded corresponding intergrain pore population. Conversely, the clay aggregations define a smaller-sized porosity. The calculation of a water retention curve derived from the pore size distribution curve showed that water retention is governed by capillarity in the largest pores between clean grains, whereas clay adsorption becomes dominant in the smallest pores, a zone where the microstructure is sensitive to change in water content. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.P.084