Correction for CPT-based fine content in improved ground

Hesham Dief

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

Session: PROBLEMATIC SOILS - III Loose and Liquefiable Soils

ABSTRACT: Stone columns are widely used for ground densification at sites prone to liquefaction in Greater Vancouver, BC. As a part of post-densification assessment and Quality Assurance, Cone Penetration Tests (CPT) can be undertaken in order to verify densification requirements. CPT results in the soils between the stone column locations have shown that the post-densification measurements of Cone Tip Resistance (qt) are greater than pre-densification values, and post-densification measurement of normalized Friction Ratio (Fr) are less than pre-densification values. This leads to an apparent decrease in the soil behavior type Index Ic values compared to the pre-densification values. The decrease of the Ic values gives a false indication of a decrease in the calculated fines content from post densification CPT relative to the pre-densification CPT. Obviously; the stone column treatment cannot reduce the soil fines content, which can be verified by laboratory tests for selected soil samples. In this study a methodology is developed to correct the estimated fines content in CPT interpretation for post-densified ground.

RÉSUMÉ: Les colonnes ballastées sont largement utilisées pour la densification des sites susceptibles à la liquéfaction dans la région de Vancouver, en Colombie-B-densification, des essais de pénétromètre statique (CPT) peuvent être faits afin de vérifier les exigences de densification. Les résultats des essais CPT dans les sols entre les emplacements de colonnes ballastées ont montré que les mesures post-densification de la Résistance de la pointe du cône (qt) sont supérieures aux valeurs de pré-densification, et les mesures post-densification du Ratio de friction (Fr) sont moins que les valeurs de pré-densification. Cela mène à une diminution c) par rapport aux valeurs de pré-densification. La c donne une fausse indication d'une diminution du contenCPT post-densification par rapport aux essais CPT pré-densification. De toute évidence, le traitement de colonne ballastées ne peut réduire le contenu fin du sol, ce qui peut être vérifié par des tests de laboratoire sur des échantillons de essais CPT d'un terrain post-densifié.

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Cite this article:
Hesham Dief (2016) Correction for CPT-based fine content in improved ground in GEO2016. Ottawa, Ontario: Canadian Geotechnical Society.

@article{3811_0802104912,author = Hesham Dief,title = Correction for CPT-based fine content in improved ground,year = 2016}