Determination of the permeability of overconsolidated clay from pressuremeter pressure hold test

Lang Liu

In the proceedings of: GeoVancouver 2016: 69th Canadian Geotechnical Conference

Session: SOIL AND TERRAIN CHARACTERIZATION - IV In-Situ Geotechnical Testing

ABSTRACT: During pressuremeter expansion, a Pressure Hold Test (PHT) conducted during the undrained expansion of the probe allows soils to consolidate in the radial direction of borehole as a result of the excess pore pressure dissipation. In this work, the PHT in an overconsolidated clay is analysed based on a variation of the soil properties and loading conditions. The analysis has been studied numerically based on an axisymmetric finite element model. From the entire range of permeability values, it is observed that the expansion reaches its peak rate at approximately 17% of total consolidation in a root time curve, which permits the graphical analysis of the consolidation stage even for a short duration PHT of around three minutes. By decoupling the effects of various soil parameters on the consolidation during hold test, a method is developed to efficiently determine horizontal permeability (kh) once other, more conventionally determined parameters are calculated. The method was applied to a series of PHTs that were performed in the deep overconsolidated clay formations in Seattle. All the necessary inputs required for the interpretation could be easily obtained. The interpretation shows a good agreement with the soils in the same region, despite a wide variation of the calculated permeabilities from all the tests.

RÉSUMÉ: Lors de l'expansion du pressiomètre, un test de maintien de pression (PHT) après une expansion non drainée permet de Dans ce travail, le PHT dans l'argile surconsolidée avec une variation des propriétés du sol et les conditions de chargement a été numériquement étudié avec un modèle d'éléments finis axisymétrique. De l'ensemble des résultats de la simulation, on observe que l'expansion atteint son sommet à 17% de consolidation dans une courbe de temps racine, ce qui nous permet d'identifier graphiquement la phase de consolidation, même pour trois minutes PHT.Une méthode est développée pour déterminer efficacement la perméabilité horizontale (kh) une fois que les autres paramètres sont donnés. Le procédé a été appliqué à une série de PHTS testées dans les formations argileuses surconsolidées profondes à test du pressiomètre comme tel. L'interprétation montre une bonne consistance pour les sols dans les mêmes régions, malgré une grande variation des perméabilités calculées à partir de tous les tests.

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