Kelly-drilled bored piles: a comparison of construction practices between Europe and North America

Supported by the Drilled Shaft Committee of Deep Foundations Institute (DFI), the similarities and differences in the bored pile foundations industry between Europe and North America were investigated, and the effort focused on five topic areas: (i) design, (ii) construction, (iii) contracting, (iv) innovations and (v) quality and testing. This paper compares and contrasts Kelly-drilled bored pile construction practices between Europe and North America, and presents the economic state of the marketplace in both Europe and North America at the time of the study. The results of the collaborative work among DFI, the European Federation of Foundation Contractors (EFFC) and numerous practitioners will be used to benchmark current industry practices, to recognise similarities and differences in practices between the two continents and markets, to disseminate solutions to similar or common problems, and to identify areas for potential improvement. By identifying and exploring national, regional and interregional differences on both continents, which made comparisons between North America and Europe more complicated, the basic assumptions and understanding of how best to design, construct, evaluate and contract work for bored piles were evaluated. A number of similarities in construction practice between Europe and North America were identified, which include: (i) the use of larger and deeper bored piles, (ii) greater focus on job site safety, (iii) increased demands imposed on the equipment including cleaner emissions and (iv) increasingly restrictive environmental regulations. Differences in practice exist throughout Europe and North America, which relate to (i) geology (spatial and composition), (ii) local vs. regional vs. national practices, (iii) concrete mix designs, (iv) performance-based vs. prescriptive-based methodology and specifications and (v) borehole stability methods (steel casing vs. bentonite or polymer slurry). The various components of the construction operation and practice contribute to the allowable or comfortable level of risk exposure of an owner, contractor and/or designer, which are typically manifested in the development and execution of the project delivery method, specifications, operating protocols and quality control and assurance programme.