Vertical Load Transfer for Bored Piles Buried in Cohesive Intermediate Geomaterials

Abstract

In developing a vertical load transfer function for bored piles buried in cohesive intermediate geomaterials (IGM), it is essential to understand the shear behavior of the rough sidewall. The interface between the cohesive IGM and the concrete shafts could be simplified as a series of identical triangular asperities. The emphasis is to quantify the collapse load of asperities due to any change in the shear-induced dilation under constant normal stiffness (CNS) conditions. An asperity model was developed and the collapse load was also derived by a lower-bound limit solution with two lines of discontinuity, and an alternative t-w curve was proposed. A design chart relevant to the material and geometric constants, including the asperity inclination and friction angle, was presented in a certain range, and a dimensionless bearing capacity factor, N, was introduced to facilitate the utilization. Case studies demonstrate that the axial load distribution predicted by the proposed method exhibits general accuracy with reference to the field observations.