Kelly-Drilled Bored Piles: A Comparison of Construction Practices Between Europe and North America-Article

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The paper compares Kelly-drilled bored pile practices in Europe and North America, based on practitioner surveys, interviews and workshops conducted by the Deep Foundations Institute and the European Federation of Foundation Contractors. Findings reflect limited survey responses—particularly from Europe—and substantial variation between regions.<br /><br />Both markets are moving toward larger, deeper, higher-capacity piles, while facing tighter site constraints, increased safety expectations and stricter environmental requirements. In both regions, ground conditions and site access are the main drivers of construction methods and equipment selection.<br /><br />Important differences include design and contracting approaches. European projects tend to use performance-based specifications and increasingly favour Design-Build, while North American practice—especially on public projects—more often uses prescriptive specifications and Design-Bid-Build. European contractors also tend to offer a broader range of foundation technologies, whereas North American specialists more often focus on particular methods.<br /><br />European piles are generally smaller in diameter but longer; North American piles tend to be larger and shallower. Europe commonly uses full-length temporary casing or mineral-based slurry to stabilize boreholes. North American contractors more often use open-hole methods, polymer slurry and, depending on location, permanent casing—particularly for bridges, scour protection and seismic resistance.<br /><br />Concrete design and quality responsibilities also differ: European contractors typically propose the mix for owner review, while North American owners more often specify strength and mix requirements. Quality assurance in North America is commonly performed by the owner or an independent agency; European contractors more often handle both quality control and assurance.<br /><br />Safety and environmental rules affect costs and productivity in both markets, with European requirements generally described as more restrictive. Overall, practices are shaped by geology, local standards, project type, risk allocation and contractor experience. The authors present the comparison as a benchmark for sharing solutions and identifying opportunities to improve design, construction, contracting and quality management.

Keywords

Kelly-drilled bored piles

foundation construction

Europe vs North America

deep foundations

Design-Build

Design-Bid-Build

temporary casing

polymer slurry

quality assurance

ground conditions