Novel experimental technique to model impression piles in centrifuge testing

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 bearing capacity, such as with the impression pile which has an enhanced shaft capacity owing 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 described, a pile made from three-dimensionally (3D)-printed rigid plastic components with a mandrel mechanism is used to create a nodular shaft surface during model making. Once assembled the pile has the same geometry as the cast-in-situ impression pile. 3D-printed plastic piles allow for fast model making and demonstrate excellent repeatability. Because of the ductile behaviour of the soil–plastic interface the impressions improve the performance of a pile over the entire load settlement curve, not just at ultimate capacity. In addition, a greater increase in ultimate capacity was registered for the 3D-printed plastic impression piles compared to similar resin impression piles. At working load, the 3D-printed plastic impression piles outperformed traditional straight-shafted piles by 90%.