Abstract:
As load demands have increased and drilling technology capabilities have improved, the casual definition of “large diameter†shaft has shifted toward larger and larger shafts. Many of today’s large diameter shafts have minimum dimensions that would classify the shafts as mass concrete under most conventional, above-ground definitions. While some public agencies have specifically exempted drilled shafts from mass concrete provisions, a growing number of other agencies have applied mass concrete provisions to drilled shafts. The presentation will introduce common variations of drilled shaft thermal provisions, present a methodology for addressing the provisions during engineering design, and summarize common construction-phase techniques for satisfying the requirements. The engineering methodology, which is based on research for FHWA and published in the Transportation Research Record, applies widely accepted techniques for above-ground concrete to drilled shafts, accounting for the benefits of drilled shaft reinforcement and concrete cover. Combined with the construction techniques, the methodology provides a means for satisfying mass concrete provisions for large diameter drilled shafts.