Journal Published Online: 21 May 2019
Volume 43, Issue 2

An Improved Unsaturated Triaxial Device to Characterize the Pore-Water Pressure and Local Volume Change Behavior of a Compacted Marl

CODEN: GTJODJ

Abstract

Compacted fills in earthworks are in an unsaturated state, with suctions (negative pore-water pressures) usually ranging from several kPa to several MPa. Characterizing the variation of pore-water pressure is a major concern in the estimation of embankment stability and, at the same time, a big challenge when its value falls below –80 kPa. This technical note presents an improved triaxial system based on the standard triaxial cell, equipped with a tensiometer, a thermocouple psychrometer, and local strain gauges. The main objective of these improvements is to measure the pore-water pressure and local volume changes during isotropic loading. In this study, three compacted specimens were tested under undrained conditions. Pore-water pressure was continuously measured by means of the psychrometric probe in the range of –3,000 to –100 kPa and by the tensiometer in the range of –80 to 1,100 kPa. Volume change was measured by the local strain gauges. Analysis and development of the results from both this study and the literature lead to the conclusions that i) specimens with occluded air bubbles (e.g., at the standard Proctor optimum) behave like a saturated soil, as Bw is close to unity when pore-water pressure becomes positive, and ii) a pore-water pressure coefficient Bw close to 1 is not necessarily a sign of saturation, as soil in an unsaturated state may also have a pore-pressure coefficient close to unity, especially at the beginning of the mechanical loading.

Author Information

Andrianatrehina, Soanarivo Rinah
Laboratoire Ondes et Milieux Complexes - CNRS UMR 6294, Normandie Université, Le Havre, France
Li, Zhong-Sen
Laboratoire de Mécanique des Sols, Structures et Matériaux - CNRS UMR 8579, Université Paris-Saclay, CentraleSupélec, Gif sur Yvette, France
Taibi, Said
Laboratoire Ondes et Milieux Complexes - CNRS UMR 6294, Normandie Université, Le Havre, France
Fleureau, Jean-Marie
Laboratoire de Mécanique des Sols, Structures et Matériaux - CNRS UMR 8579, Université Paris-Saclay, CentraleSupélec, Gif sur Yvette, France
Boutonnier, Luc
Egis Géotechnique, Seyssins, France
Pages: 12
Price: $25.00
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Details
Stock #: GTJ20190003
ISSN: 0149-6115
DOI: 10.1520/GTJ20190003