Undrained shear strength from piezocone tests

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Journal titleCanadian Geotechnical Journal
Pages392405; # of pages: 14
Subjectpenetrometers; shear strength; sensitive clay; soft clay; penetrometers; mechanical resistance; induced pore pressures; soil penetration; cavity expansion pressure; tip resistance; effective friction; cone - soil interface; self-boring pressuremeter tests; soil rigidity index; cavity expansion modelling; soft sensitive clay; stiff sensitive clay; clayey silt; ckou triaxial strength; soil brittleness; soil behaviour; excess pore-water pressure; strength determination prarameters
AbstractWith the advent of piezocones -- penetrometers measuring both the mechanical resistance and induced pore pressures near the tip during penetration into the soil -- a new interpretation of penetrometer test data is possible. This paper presents a review of available interpretation methods for obtaining the undrained shear strength of soft soils, and introduces a new interpretation taking into account measured pore pressures. The undrained shear strength is considered to be solely related to the ultimate cavity expansion pressure, which is one of the components of the tip resistance. The other component is calculated assuming that effective friction is developed at the cone -- soil interface. Parametric studies on the parameters required for strength determination based on the proposed method are also presented. Special self-boring pressuremeter tests to obtain relevant values of soil rigidity index, which is a key parameter for cavity expansion modelling, are described. Tests were conducted at three sites having the characteristics of soft sensitive clay, stiff sensitive clay, and clayey silt. The operational undrained strength mobilized during the cone insertion derived from the proposed model is equal to or lower than the CKsub0U triaxial strength, which depends on soil brittleness. The proposed approach yields results consistent with known soil behaviour at all three sites.
Publication date
AffiliationNRC Institute for Research in Construction; National Research Council Canada
Peer reviewedYes
NRC number28555
NPARC number20331514
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Record identifier6835ad29-4cf1-4ab1-ac7a-b0b062fae6ec
Record created2012-07-18
Record modified2016-05-09
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