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Interpretation of T-bar penetrometer tests at shallow embedment and in very soft soils

Interpretation of T-bar penetrometer tests at shallow embedment and in very soft soils
Interpretation of T-bar penetrometer tests at shallow embedment and in very soft soils

The cylindrical T-bar penetrometer was developed for profiling the undrained strength of soft soils in the centrifuge and is now a widely-used offshore site investigation tool. The conventional interpretation of the T-bar test is to convert the measured penetration resistance to soil strength using a single bearing factor associated with steady flow of soil around the bar. This paper describes a new analysis for the interpretation of T-bar penetrometer tests at shallow embedment and in soft soils, which is an increasingly significant consideration in the design of seabed infrastructure, including pipelines. The analysis captures two mechanisms that are usually neglected: (i) soil buoyancy and (ii) the reduced bearing factor arising from the shallow failure mechanism mobilized prior to the full flow of soil around the bar. The framework derives from theoretical considerations and is calibrated using large deformation finite element analyses. The depth at which the steady deep penetration condition is reached is shown to depend on the normalized soil strength, su/γ'D, and may be up to several diameters deep. The effect of this new procedure on the inferred soil strength compared with the conventional approach is illustrated through T-bar tests in three different centrifuge samples, spanning a range of strength ratios.

Centrifuge, Penetrometer, Soft soil, T-bar
0008-3674
218-229
White, D.J.
a986033d-d26d-4419-a3f3-20dc54efce93
Gaudin, C.
4d1197f0-7c69-4301-8877-33f840784685
Boylan, N.
e9ddfa83-2c78-4d46-83c4-3414e5adc65a
Zhou, H.
8341ffe7-8014-4a11-8d2a-c353b127b898
White, D.J.
a986033d-d26d-4419-a3f3-20dc54efce93
Gaudin, C.
4d1197f0-7c69-4301-8877-33f840784685
Boylan, N.
e9ddfa83-2c78-4d46-83c4-3414e5adc65a
Zhou, H.
8341ffe7-8014-4a11-8d2a-c353b127b898

White, D.J., Gaudin, C., Boylan, N. and Zhou, H. (2010) Interpretation of T-bar penetrometer tests at shallow embedment and in very soft soils. Canadian Geotechnical Journal, 47 (2), 218-229. (doi:10.1139/T09-096).

Record type: Article

Abstract

The cylindrical T-bar penetrometer was developed for profiling the undrained strength of soft soils in the centrifuge and is now a widely-used offshore site investigation tool. The conventional interpretation of the T-bar test is to convert the measured penetration resistance to soil strength using a single bearing factor associated with steady flow of soil around the bar. This paper describes a new analysis for the interpretation of T-bar penetrometer tests at shallow embedment and in soft soils, which is an increasingly significant consideration in the design of seabed infrastructure, including pipelines. The analysis captures two mechanisms that are usually neglected: (i) soil buoyancy and (ii) the reduced bearing factor arising from the shallow failure mechanism mobilized prior to the full flow of soil around the bar. The framework derives from theoretical considerations and is calibrated using large deformation finite element analyses. The depth at which the steady deep penetration condition is reached is shown to depend on the normalized soil strength, su/γ'D, and may be up to several diameters deep. The effect of this new procedure on the inferred soil strength compared with the conventional approach is illustrated through T-bar tests in three different centrifuge samples, spanning a range of strength ratios.

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More information

Published date: February 2010
Keywords: Centrifuge, Penetrometer, Soft soil, T-bar

Identifiers

Local EPrints ID: 419646
URI: http://eprints.soton.ac.uk/id/eprint/419646
ISSN: 0008-3674
PURE UUID: 4694b321-8d48-4db4-b6fb-061196a813be
ORCID for D.J. White: ORCID iD orcid.org/0000-0002-2968-582X

Catalogue record

Date deposited: 18 Apr 2018 16:30
Last modified: 26 Nov 2019 01:25

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