An experimental study into the ultimate capacity of an ‘impression’ pile in clay

Lalicata, Leonardo Maria; Stallebrass, S. E.; McNamara, A. M.

doi:10.1680/jgeot.21.00168

Cited by 3 publications

(3 citation statements)

References 23 publications

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“…This section provides a brief summary of the centrifuge tests undertaken by . The complete details of the experimental arrangement and of the test results are given elsewhere (Lalicata et al, 2020;. The Geotechnical Engineering Research Group at City, University of London, makes use of an Acutronic 661 beam centrifuge, described in detail by Schofield and Taylor (1988).…”

Section: Experimental Evidences: the Centrifuge Testsmentioning

confidence: 99%

“…A special tool has been developed by Keltbray Piling to undertake this profiling, at prototype scale, and create what has been termed an "impression pile" (Keltbray Piling, 2020). Lalicata et al (2020) developed a small-scale impression tool for centrifuge model testing. carried out an extensive parametric study in the geotechnical centrifuge to explore the influence of impressions on the ultimate capacity of a pile.…”

Section: Introductionmentioning

confidence: 99%

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Design method for the ‘impression pile’

Lalicata

Stallebrass

McNamara

et al. 2022

Proceedings of the Institution of Civil Engineers - Geotechnica

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Urban development in congested cities requires a better exploitation of the available surface, leading to taller structures. These buildings are usually founded on piles that have to be increased in dimension to accommodate the larger loads, resulting in increases in both the cost and the carbon dioxide footprint of the pile foundation. An alternative option is to improve pile performance by enhancing the shaft capacity, which is commonly the most important factor in determining the ultimate capacity of a pile constructed in a clay soil subjected to axial load. For piles in stiff clays such as London Clay, the soil–pile friction may be increased by profiling the side walls of a bored cast in situ pile with small discrete ‘impressions’ such that the latter form nodules on the shaft of the concreted pile. Centrifuge tests carried out at City, University of London, and field trials undertaken by Keltbray Piling across different London sites showed an increase in the shaft capacity of around 40%. In this work, a simple design method based on experimental evidence and an existing plastic failure mechanism was derived for ‘impression’ piles. The proposed method shows good agreement with data and enables a direct prediction of the increase in capacity for future designs.

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Section: Experimental Evidences: the Centrifuge Testsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Design method for the ‘impression pile’

Lalicata

Stallebrass

McNamara

et al. 2022

Proceedings of the Institution of Civil Engineers - Geotechnica

Self Cite

View full text Add to dashboard Cite

show abstract

“…Impression piles out-perform traditional bored piles in stiff clays providing additional shaft capacity from impressions that generate a nodular pile surface (Lalicata et al, 2022(Lalicata et al, , 2023. The performance of the impression piles depends on the quality of indentations.…”

Section: Introductionmentioning

confidence: 99%

Forces required to create impressions in clay

Lalicata

Stallebrass

McNamara

2023

Preprint

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Several centrifuge and full-scale tests have demonstrated that an impression pile provides increased geotechnical capacity of up to 40% compared to a straight shafted pile depending on the quality of the indentations. The feasibility of creating indentations is governed by the strength of the clay, the capacity of the jack used in the impression tool, the impression shape and the area being impressed. Model tests and limit analyses have been carried out to optimise the impression tool. Results show that a flat-end or a flat-conical tip represents the best compromise between the need to reduce bearing capacity of the tip whilst maximising the indentation depth. Indentations must be spaced by at least 3 times their width to ensure a well-constructed impression pile with independent indentations.

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Novel experimental technique to model impression piles in centrifuge testing

Lalicata,

Ritchie,

Stallebrass

et al. 2024

International Journal of Physical Modelling in Geotechnics

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A novel experimental technology for small scale centrifuge tests on piled foundations has been investigated. The technology is suitable for bored piles where the pile shaft has been profiled to improve the bearing capacity. One such pile is an impression pile that has an enhanced shaft capacity due to the small impressions created along the shaft. In previous centrifuge testing, impression piles have been created by pouring resin into a profiled bore. However, in the technique to be described a novel pile made of 3D printed rigid plastic with a reverse mandrel mechanism is used to create a nodular shaft surface during installation in the clay sample. Once assembled the pile has the same geometry as the cast in situ impression pile. Compared to the resin piles, 3D printed plastic piles allow for faster model making and demonstrate excellent repeatability. Because of the ductile behaviour of the soil-plastic interface it is possible to see how the impressions improve the performance of a pile over the whole load-settlement curve, not just at ultimate capacity. In addition, a greater percentage increase in ultimate capacity was registered for the 3D printed plastic impression piles compared to similar resin impression piles. The plastic-soil interface has an α value which is closer to that commonly encountered in the field. At working load, the 3D printed plastic impression piles outperformed traditional straight shafted piles by 90%.

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An experimental study into the ultimate capacity of an ‘impression’ pile in clay

Abstract: An experimental study into the ultimate capacity of an "impression" pile in clay

Cited by 3 publications

References 23 publications

Design method for the ‘impression pile’

Design method for the ‘impression pile’

Forces required to create impressions in clay

Novel experimental technique to model impression piles in centrifuge testing

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