Use of the Impression Pile to Reduce Carbon EmissionsÂ-Paper

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The paper evaluates impression piles as a way to reduce the carbon footprint of foundations for tall buildings. Conventional piles often require substantial concrete and deep excavation to carry heavy loads, increasing embodied emissions, spoil removal, and construction impacts.<br /><br />An impression pile is a bored cast-in-place pile whose exposed shaft is profiled with a hydraulic tool to form discrete soil-filled nodules. These features shift load transfer from the concrete–soil interface toward a more effective soil–soil shear mechanism. Centrifuge testing and full-scale trials indicate that impressions can increase shaft capacity by up to about 40% compared with an otherwise identical straight-shaft pile.<br /><br />The additional capacity can be used either to support greater loads or to maintain the same capacity with a shorter pile. In the paper’s example, for an adhesion factor of 0.5, pile length could be reduced by around 40% for a 700 mm diameter pile and 30% for a 1,000 mm pile. Across the diameter range considered, an average length reduction of about 25% is estimated, corresponding to a similar reduction in concrete-related embodied carbon. The extra concrete required for the nodules is small—about 2% or less of the pile volume—and shorter piles may also reduce transport and spoil-removal emissions.<br /><br />The authors conclude that impression piles offer a practical way to improve foundation efficiency and support lower-carbon construction. Actual savings depend on soil conditions, pile dimensions, and nodule configuration, and the benefits at working loads and the feasibility of forming impressions at depth require further assessment.

Keywords

impression piles

carbon footprint

foundations

tall buildings

bored cast-in-place pile

shaft capacity

embodied carbon

load transfer

concrete emissions

foundation efficiency