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Investigation of pile penetration in calcareous soft rock using X-ray computed tomography

Investigation of pile penetration in calcareous soft rock using X-ray computed tomography
Investigation of pile penetration in calcareous soft rock using X-ray computed tomography

Penetration of open- and closed-ended model piles into intact chalk, a soft calcareous rock, was investigated using microfocus X-ray computed tomography (XCT). Three-dimensional images of the specimens showed that the piles crushed and densified the chalk in their path, creating a crushed chalk annulus around the shaft, a region of compressed destructured chalk below the tip, and fractures across cemented regions of the specimen. Laser-diffraction particle-size analyses of the crushed chalk annulus after exhumation showed limited difference with laboratory-remoulded chalk, which suggested thorough de-cementation. Installation stresses and XCT-derived densities were paired using a simplified cylindrical cavity expansion solution to estimate effective radial stress–void ratio states at the pile tip during penetration. More complex numerical solutions could not be applied using the available data. This approach posed significant problems, as it could not suitably incorporate hardening and non-linear stiffness behaviours of chalk during pile penetration, nor account for the creation of discontinuities. However, effective radial stress–void ratio estimates were found to converge with the reconstituted critical state line of the material at high stresses and low void ratios. This partially supported the use of a critical state framework to characterise pile penetration in chalk, as proposed in recent literature.

chalk, model tests, piles & piling
1346-213X
38-52
Alvarez-Borges, Fernando
5512cdfd-6ad3-475f-8aec-2fc767607314
Ahmed, Sharif
e7181acb-a5ad-4712-b6bd-4c4dfbf6a9dc
Madhusudhan, Bangalore Narasimha
e139e3d3-2992-4579-b3f0-4eec3ddae98c
Richards, David
a58ea81e-443d-4dab-8d97-55d76a43d57e
Alvarez-Borges, Fernando
5512cdfd-6ad3-475f-8aec-2fc767607314
Ahmed, Sharif
e7181acb-a5ad-4712-b6bd-4c4dfbf6a9dc
Madhusudhan, Bangalore Narasimha
e139e3d3-2992-4579-b3f0-4eec3ddae98c
Richards, David
a58ea81e-443d-4dab-8d97-55d76a43d57e

Alvarez-Borges, Fernando, Ahmed, Sharif, Madhusudhan, Bangalore Narasimha and Richards, David (2022) Investigation of pile penetration in calcareous soft rock using X-ray computed tomography. International Journal of Physical Modelling in Geotechnics, 22 (1), 38-52, [jphmg.20.00031]. (doi:10.1680/jphmg.20.00031).

Record type: Article

Abstract

Penetration of open- and closed-ended model piles into intact chalk, a soft calcareous rock, was investigated using microfocus X-ray computed tomography (XCT). Three-dimensional images of the specimens showed that the piles crushed and densified the chalk in their path, creating a crushed chalk annulus around the shaft, a region of compressed destructured chalk below the tip, and fractures across cemented regions of the specimen. Laser-diffraction particle-size analyses of the crushed chalk annulus after exhumation showed limited difference with laboratory-remoulded chalk, which suggested thorough de-cementation. Installation stresses and XCT-derived densities were paired using a simplified cylindrical cavity expansion solution to estimate effective radial stress–void ratio states at the pile tip during penetration. More complex numerical solutions could not be applied using the available data. This approach posed significant problems, as it could not suitably incorporate hardening and non-linear stiffness behaviours of chalk during pile penetration, nor account for the creation of discontinuities. However, effective radial stress–void ratio estimates were found to converge with the reconstituted critical state line of the material at high stresses and low void ratios. This partially supported the use of a critical state framework to characterise pile penetration in chalk, as proposed in recent literature.

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e-pub ahead of print date: 11 January 2021
Published date: 1 January 2022
Additional Information: Funding Information: This research has been sponsored by the National Council of Science and Technology of Mexico (Consejo Nacional de Ciencia y Tecnología, CONACyT) and by the Faculty of Engineering and Physical Sciences of the University of Southampton. The authors are grateful for the support of Dr Mark Mavrogordato, Dr Orestis Katsamenis and Dr Kathryn Rankin from the μ-Vis X-ray Imaging Centre of the University of Southampton. Funding Information: This research has been sponsored by the National Council of Science and Technology of Mexico (Consejo Nacional de Ciencia y Tecnolog?a, CONACyT) and by the Faculty of Engineering and Physical Sciences of the University of Southampton. The authors are grateful for the support of Dr Mark Mavrogordato, Dr Orestis Katsamenis and Dr Kathryn Rankin from the ?-Vis X-ray Imaging Centre of the University of Southampton. Publisher Copyright: © 2022 ICE Publishing. All rights reserved.
Keywords: chalk, model tests, piles & piling

Identifiers

Local EPrints ID: 450015
URI: http://eprints.soton.ac.uk/id/eprint/450015
ISSN: 1346-213X
PURE UUID: 83961f81-bff1-4be4-b3f0-aef9877c3d24
ORCID for Fernando Alvarez-Borges: ORCID iD orcid.org/0000-0002-6940-9918
ORCID for Bangalore Narasimha Madhusudhan: ORCID iD orcid.org/0000-0002-2570-5934

Catalogue record

Date deposited: 05 Jul 2021 16:31
Last modified: 31 Jan 2023 03:06

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Contributors

Author: Fernando Alvarez-Borges ORCID iD
Author: Sharif Ahmed
Author: David Richards

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