Upper-bound analysis of uplift piles in nonhomogeneous clay using streamline velocity fields

An axisymmetric streamline velocity field is developed and applied to the upper-bound analysis of uplift piles in undrained clay with a linear relationship between undrained strength and depth. The obtained upper-bound uplift bearing capacity factors (Nc) are verified by comparing with elastoplastic finite-element and existing lower-bound solutions. Parametric studies are carried out to investigate the variation of Nc with different embedment ratios, pile roughness and undrained strength profile. A formulation predicting the upper-bound capacity of uplift piles in clay is proposed. Finally, its reliability is assessed by comparing with existing laboratory and field test results.