A comparative field study of free-fall cone and sphere penetrometers in soft sediment
A comparative field study of free-fall cone and sphere penetrometers in soft sediment
This paper describes the field performance of two instrumented free-fall penetrometers (FFPs), which offer the possibility of low cost rapid strength profiling without requiring the equipment associated with conventional CPTs or drilling and sampling. The devices considered are a free-fall cone penetrometer (FFcP) and an instrumented free-fall sphere (IFFS). The performance of the FFPs in assessing soil undrained shear strength was investigated and compared through field trials in the soft sediments of the Swan River, Perth, Western Australia. The penetrometers achieved impact velocities of 1.4–5.8 m/s from drop heights of 0.7–3.0 m above the riverbed, and embedded to depths of up to 1.6 times the FFP length (1.45 m) and 4.5 times the IFFS diameter (0.89 m). The FFP data provided the shear strength indirectly using the acceleration measured from an onboard inertial measurement unit. The accuracy depends on the assumptions made regarding the magnitude of dynamic bearing and shaft frictional resistance. Uncertainty associated with dynamic bearing resistance causes a ±10% and ±13% variation in the calculated strength for the IFFS and the FFcP, respectively. However, the equivalent uncertainty in dynamic shaft resistance can cause a variation in the calculated strength of up to ±76% for the FFcP. The FFcP has higher embedment potential than the IFFS, but the IFFS has the advantage of a simpler interpretation without needing to account for dynamic shaft resistance.
Clay, Dynamic embedment, Field tests, Free-fall penetrometer, Undrained shear strength, Free -fall penetrometer
Chow, S. H.
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O'Loughlin, C. D.
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McIlduff, R.
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White, D. J.
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Chow, F. C.
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Goh, C.L.V.
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15 July 2023
Chow, S. H.
7bbb0ede-4e74-46ad-8586-425fa5d2672a
O'Loughlin, C. D.
cd36a0df-e345-48fa-9f35-2a43f2cdda6f
McIlduff, R.
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White, D. J.
a986033d-d26d-4419-a3f3-20dc54efce93
Chow, F. C.
89ea88e4-b7da-4f81-b4ee-5305d4730d93
Goh, C.L.V.
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Chow, S. H., O'Loughlin, C. D., McIlduff, R., White, D. J., Chow, F. C. and Goh, C.L.V.
(2023)
A comparative field study of free-fall cone and sphere penetrometers in soft sediment.
Ocean Engineering, 280, [114094].
(doi:10.1016/j.oceaneng.2023.114094).
Abstract
This paper describes the field performance of two instrumented free-fall penetrometers (FFPs), which offer the possibility of low cost rapid strength profiling without requiring the equipment associated with conventional CPTs or drilling and sampling. The devices considered are a free-fall cone penetrometer (FFcP) and an instrumented free-fall sphere (IFFS). The performance of the FFPs in assessing soil undrained shear strength was investigated and compared through field trials in the soft sediments of the Swan River, Perth, Western Australia. The penetrometers achieved impact velocities of 1.4–5.8 m/s from drop heights of 0.7–3.0 m above the riverbed, and embedded to depths of up to 1.6 times the FFP length (1.45 m) and 4.5 times the IFFS diameter (0.89 m). The FFP data provided the shear strength indirectly using the acceleration measured from an onboard inertial measurement unit. The accuracy depends on the assumptions made regarding the magnitude of dynamic bearing and shaft frictional resistance. Uncertainty associated with dynamic bearing resistance causes a ±10% and ±13% variation in the calculated strength for the IFFS and the FFcP, respectively. However, the equivalent uncertainty in dynamic shaft resistance can cause a variation in the calculated strength of up to ±76% for the FFcP. The FFcP has higher embedment potential than the IFFS, but the IFFS has the advantage of a simpler interpretation without needing to account for dynamic shaft resistance.
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Accepted/In Press date: 2 March 2023
e-pub ahead of print date: 14 May 2023
Published date: 15 July 2023
Additional Information:
Funding Information:
The field work was supported by the Woodside RiverLab initiative with The University of Western Australia , which aims to develop innovations in offshore engineering via research, education and outreach. Development and fabrication of the free-fall penetrometers was funded by the Remote Intelligent Geotechnical Seabed Surveys (RIGSS) Joint Industry Project, supported by Fugro , Shell , Total and Woodside Energy Ltd. The second author acknowledges the support provided by the ARC ITRH for Transforming energy Infrastructure through Digital Engineering (TIDE, http://TIDE.edu.au ) which is led by The University of Western Australia , delivered with The University of Wollongong and several other Australian and International research partners, and funded by the Australian Research Council , INPEX Operations Australia, Shell Australia, Woodside Energy, Fugro Australia Marine, Wood Group Kenny Australia, RPS Group, Bureau Veritas and Lloyd's Register Global Technology (Grant No. IH200100009 ).
Publisher Copyright:
© 2023
Keywords:
Clay, Dynamic embedment, Field tests, Free-fall penetrometer, Undrained shear strength, Free -fall penetrometer
Identifiers
Local EPrints ID: 478979
URI: http://eprints.soton.ac.uk/id/eprint/478979
ISSN: 0029-8018
PURE UUID: afeab7d6-f242-433b-a17d-8edd42ed3ed5
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Date deposited: 17 Jul 2023 16:34
Last modified: 18 Mar 2024 03:42
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Contributors
Author:
S. H. Chow
Author:
C. D. O'Loughlin
Author:
R. McIlduff
Author:
F. C. Chow
Author:
C.L.V. Goh
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