Documents disponibles écrits par cet auteur

Effect of soil conditioners on the pressure and rate-dependent shear strength of different clays / R. Zumsteg in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 9 (Septembre 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 9 (Septembre 2012) . - pp.1138–1146. Titre : Effect of soil conditioners on the pressure and rate-dependent shear strength of different clays Type de document : texte imprimé Auteurs : R. Zumsteg, Auteur ; M. Plotze, Auteur ; A. M. Puzrin, Auteur Année de publication : 2012 Article en page(s) : pp.1138–1146. Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Soil  conditioning  Clay  pastes  Vane  shear  test  Viscosity  of  clays  Clay-polymer  mixtures  Earth  pressure  balance Résumé : Tunneling using the earth pressure balance machines method in clayey soils requires the addition of conditioning chemicals to reduce the torque moment of the machine and to guarantee a safe and economical excavation process. Injection of foams and polymers at the cutter head of the tunnel boring machine with subsequent remolding in the pressure chamber transforms the excavated material into a deformable soil paste with preferably low strength and adhesion. The soil becomes more compressible and can develop viscous properties, such that the pressure and rate dependency of the shear strength of the mixtures are of major importance for the proper design and analysis of the tunneling processes. In this paper, the results of vane shear strength measurements on various conditioned clays and clay-sand mixtures at various shearing velocities and applied pressures are presented and analyzed. The results clearly show the effects of the chemicals used and also point out the differences in their efficiency depending on the clay mineralogy. This allows for an improved understanding of the working mechanisms of the chemicals. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000681 [article] Effect of soil conditioners on the pressure and rate-dependent shear strength of different clays [texte imprimé] / R. Zumsteg, Auteur ; M. Plotze, Auteur ; A. M. Puzrin, Auteur . - 2012 . - pp.1138–1146. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 9 (Septembre 2012) . - pp.1138–1146. Mots-clés : Soil  conditioning  Clay  pastes  Vane  shear  test  Viscosity  of  clays  Clay-polymer  mixtures  Earth  pressure  balance Résumé : Tunneling using the earth pressure balance machines method in clayey soils requires the addition of conditioning chemicals to reduce the torque moment of the machine and to guarantee a safe and economical excavation process. Injection of foams and polymers at the cutter head of the tunnel boring machine with subsequent remolding in the pressure chamber transforms the excavated material into a deformable soil paste with preferably low strength and adhesion. The soil becomes more compressible and can develop viscous properties, such that the pressure and rate dependency of the shear strength of the mixtures are of major importance for the proper design and analysis of the tunneling processes. In this paper, the results of vane shear strength measurements on various conditioned clays and clay-sand mixtures at various shearing velocities and applied pressures are presented and analyzed. The results clearly show the effects of the chemicals used and also point out the differences in their efficiency depending on the clay mineralogy. This allows for an improved understanding of the working mechanisms of the chemicals. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000681

Smear zone identification and soil properties around stone columns constructed in-flight in centrifuge model tests / T. M. Weber in Géotechnique, Vol. 60 N° 3 (Mars 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 3 (Mars 2010) . - pp. 197–206 Titre : Smear zone identification and soil properties around stone columns constructed in-flight in centrifuge model tests Type de document : texte imprimé Auteurs : T. M. Weber, Auteur ; M. Plotze, Auteur ; J. Laue, Auteur Année de publication : 2011 Article en page(s) : pp. 197–206 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Ground  improvement  Model  tests  Clay  Microscopy  Fabric/structure  of  soil Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Stone columns are primarily used for the purpose of ground improvement in fine grained soils in order to reduce settlements and the risk of bearing failure. They are also designed to improve the drainage conditions in the ground and to accelerate the consolidation processes within the clay. However, smear and disturbing effects caused during the construction of stone columns result in degradation of consolidation performance in comparison with the theoretically ideal conditions. Model stone columns are constructed in-flight under 50 times gravity in centrifuge tests and the soil micro-structure in the vicinity of these columns is investigated by applying different methods, including environmental scanning electron microscopy and mercury intrusion porosimetry. The results of these tests confirm that smear and disturbance occur owing to stone column installation and the region influenced can be divided into three sections: a penetration zone (1) where the sand particles are squeezed through the clay; a smear zone (2) where the soil particles have experienced a significant reorientation; and a densification zone (3) where the structure of the clay does not appear to change, but compaction of the clay is measurable. The extremes of the disturbed zone around model stone columns are determined to extend to about 2·5 times the column radius. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.098 [article] Smear zone identification and soil properties around stone columns constructed in-flight in centrifuge model tests [texte imprimé] / T. M. Weber, Auteur ; M. Plotze, Auteur ; J. Laue, Auteur . - 2011 . - pp. 197–206. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 3 (Mars 2010) . - pp. 197–206 Mots-clés : Ground  improvement  Model  tests  Clay  Microscopy  Fabric/structure  of  soil Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Stone columns are primarily used for the purpose of ground improvement in fine grained soils in order to reduce settlements and the risk of bearing failure. They are also designed to improve the drainage conditions in the ground and to accelerate the consolidation processes within the clay. However, smear and disturbing effects caused during the construction of stone columns result in degradation of consolidation performance in comparison with the theoretically ideal conditions. Model stone columns are constructed in-flight under 50 times gravity in centrifuge tests and the soil micro-structure in the vicinity of these columns is investigated by applying different methods, including environmental scanning electron microscopy and mercury intrusion porosimetry. The results of these tests confirm that smear and disturbance occur owing to stone column installation and the region influenced can be divided into three sections: a penetration zone (1) where the sand particles are squeezed through the clay; a smear zone (2) where the soil particles have experienced a significant reorientation; and a densification zone (3) where the structure of the clay does not appear to change, but compaction of the clay is measurable. The extremes of the disturbed zone around model stone columns are determined to extend to about 2·5 times the column radius. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.098