Abstract:
When good design, construction and quality assurance/quality control (QA/QC) procedures are followed, both side and base resistance contribute to drilled shaft rock socket axial resistance. Particularly in the past two decades as bi-directional axial load testing has become commonplace, there is now a wealth of data from full-scale load tests of rock-socketed drilled shafts that demonstrate this behavior. Nonetheless, there are agencies and individual engineers that continue to disregard either side or base resistance for reasons that contradict available evidence, often resulting in excessive rock socket lengths that increase costs and the risk of problems during construction. The purpose of this presentation is to provide a summary of the recent evidence indicating mobilization of combined side and base resistances at acceptable levels of displacement in well-designed, constructed and inspected rock sockets. There are geological settings in which mobilization of side and/or base resistance may not be reliable, but those situations are the exception, not the rule.