A general load-transfer formulation for the base resistance of large-diameter open-ended pipe piles driven in sand

At the previous symposium, a new ‘unified’ CPT-based design method for estimating the axial capacity of driven piles in sand was introduced. This method has replaced all its predecessors in the design standard ISO/DIS 19901- 4:2022. The method estimates both the shaft resistance and the base resistance at a displacement of 10% of the pile diameter. However, when assessing the performance of a foundation, estimating the pile settlement as a function of the applied load is just as important as determining the ultimate bearing capacity. In addition to considering the compressibility of the pile, load-transfer curves for the pile shaft and base are required to estimate this settlement. As general load-transfer curves for the pile base of open-ended pipe piles are lacking, this paper focuses on these. A general load-transfer formulation is presented, adhering to the new ‘unified’ CPT-based design method. The formulation is also evaluated against test data, showing good agreement. Based on this, it is concluded that the base response of large-diameter open-ended pipe piles significantly differs from that of closed-ended piles and require its own formulation.