Pile driving in soft ground and mitigation measures to minimise impact on existing infrastructure-Paper

Paper

Pdf Summary

The paper examines how groups of driven precast concrete piles can affect nearby infrastructure when installed through deep soft clay, using a freeway project in Melbourne, Australia. In these soils, pile installation displaces ground that cannot readily compact, potentially causing substantial heave and lateral movement over considerable distances.<br /><br />The project’s ground profile included up to 20 m of soft Coode Island Silt above firmer soils and dense sands. To assess risk, engineers conducted pre-production pile trials and monitored ground movement with inclinometers. The trial data were used to calibrate a three-dimensional PLAXIS finite-element model, which was then applied to predict movements for full pile groups and evaluate mitigation options.<br /><br />The measures assessed included pre-boring, steel casing combined with pre-boring, and replacing concrete piles with low-displacement steel H-piles. Pre-boring and casing reduced peak horizontal displacement by approximately 20%. Trials of the H-pile option also indicated substantially lower ground movement; displacement near one test pile was measured at less than 2.5 mm.<br /><br />The study emphasizes that predictions should be validated against site-specific trials and monitoring. Calibrated modelling, targeted mitigation, and continued measurement during construction enabled the project team to refine assumptions and manage potential impacts on existing structures and assets.

Keywords

precast concrete piles

soft clay

ground movement

heave

lateral displacement

PLAXIS model

pile trials

pre-boring

steel casing

H-piles