Large-scale laboratory assessment of smear effects in soft soils stabilized by prefabricated vertical drains

Ali Ghandeharioon

In the proceedings of: GeoManitoba 2012: 65th Canadian Geotechnical Conference

Session: M2A - Ground Improvement

ABSTRACT: A number of large-scale laboratory tests that incorporated the field conditions and effects of confining pressures were performed to evaluate the smear effects in soft clays stabilized by prefabricated vertical drains (PVDs). A consolidometer specifically designed for this purpose, and a machine capable of driving mandrels at realistic rates were used in these experiments. Different surcharge loads were applied while installing PVDs in the laboratory. The variations of pore water pressure during installation of the mandrel-driven PVD and withdrawal of the mandrel were monitored in the tests by fast response pore pressure transducers connected to a digital data logger. Distinct instants of change in the developed excess pore pressure were identified as the mandrel was installed and then withdrawn. The extent of smear zone in the large-scale consolidometer was examined using the results of moisture content tests on samples, which were cored along different polar axes from various locations. The results verified the concept of an elliptical smear zone around vertical drains driven by mandrels commonly used the field. The smear zone was then analyzed to establish a relationship between its size and the in-situ effective stresses.

RÉSUMÉ: ais de laboratoire à grande échelle incorporant les conditions sur le terrain et les effets de pressions de confinement ont été réalisés pour évaluer les effets de souillure dans les argiles molles stabilisées par drains verticaux préfabriqués (PVD). Un consolidomètre spécialement conçu à cet effet et une machine capable de foncer des mandrins à des taux réalistes ont été utilisés lors de ces essais. Différentes charges additionnelles ont été appliquées lors de l'installation des PVD en laboratoire. Les variations de pression d'eau interstitielle lors de réponse rapide connectés à un enregistreur de données numériques. Des points de changement dans les pressions dans le consolidomètre à grande échelle a été examinée en utilisant les déterminations de teneur en eau sur des échantillons prélevés par carottage à différents endroits selon un système d'axes polaires. Les résultats ont confirmé le concept d'une zone de souillure elliptique autour des drains verticaux entraînés par des mandrins couramment utilisés sur le terrain. La zone de souillure a été ensuite analysée pour établir une relation entre sa taille et les contraintes effectives in situ.

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Cite this article:
Ali Ghandeharioon (2012) Large-scale laboratory assessment of smear effects in soft soils stabilized by prefabricated vertical drains in GEO2012. Ottawa, Ontario: Canadian Geotechnical Society.

@article{Paper122,author = Ali Ghandeharioon,title = Large-scale laboratory assessment of smear effects in soft soils stabilized by prefabricated vertical drains,year = 2012}