Correlation between the PDA-Derived Pile Side Resistance and Undrained Shear Strength of Clays in Alberta

ABSTRACT: For many centuries, piles have been used to support structures; however, challenges still arise to accurately predict the ultimate axial capacity of a pile. The main challenges are due to the inconsistent soil conditions, pile installation effects, and errors by site investigation techniques. The goal of this study was to improve the accuracy of design methods for the pile side resistance in cohesive soils by proposing a new approach. The new design method attempts to empirically consider the pile length and load-transfer effects. A database of 128 driven pipe piles was collected from a site in Alberta and applied in this study. The piles were subjected to Pile Driving Analyzer (PDA) tests, and the surrounding soil was investigated with borehole drilling and pocket pen measurements. The soil stratigraphy at this site is relatively consistent, composed of sand underlain by stiff clay (till). A study was conducted to correlate the side resistance obtained from PDA tests to the undrained shear strengths measured by pocket pens. A new design method was proposed with a coefficient of determination (𝑅2) of 0.81 between the measured and predicted unit side resistances, and it offered significant improvements compared to existing methods. The findings will assist practitioners to deliver more reliable pile designs, particularly in Alberta soils.