A New Failure Load Criterion for Large-Diameter Under-Reamed Piles: Practical Perspective

Sustainable performance of heavy structures such as tanks, storage yards and tall buildings often rely on an efficient transfer of vertical and lateral loads to underlying ground. If the foundation soil does not have sufficient strength, the piles may be belled out (under-reamed) at the base, often termed as large-diameter belled piles (LDBPs). In reality the deformation and failure mechanism of LDBPs are significantly different and are influenced by the nature of foundation soil. However, in the absence of appropriate design guidelines, LDBPs are simply treated as conventional straight piles, often ignoring enlarged base. To access effects of enlarged base on load-deformation behavior, full-scale load tests are conducted on several LDBPs. A novel interpreted failure load criterion is proposed for LDBPs. The general applicability of this criterion is verified using the data from nine independent pile load tests retrieved from four different projects across China. Adopting the proposed method, provision of a much effective and economic design for LDBPs is feasible in comparison with the criteria currently prevalent in practice.