AN AXISYMMETRIC MODEL FOR ULTIMATE CAPACITY OF A SINGLE PILE IN SAND

Adel M. Hanna, and T. Q. Nguyen

ABSTRACT: Conventional theories for predicting the capacity of a single pile in sand have not been able to support the undisputed experimental results, which originated the concept of the critical depth (Kerisel, 1961; Vesic, 1967 and Tavenas, 1971). Furthermore, the predictions obtained from these theories are wide (Poulos and Davis,1980).
 An axisymmetric model was developed to predict the capacity of a single, vertical pile in sand, subjected to axial loading. The proposed model incorporates salient features previously neglected in conventional theories, viz. the interaction between the shaft and the tip resistance, coupled with a punching shear mechanism as a unique mode of failure. This model signifies a distinct departure from existing methods, which calculate the shaft resistance, based on a mechanism independent of tip resistance. The model is also capable of accounting for the effects of the sand density, the initial lateral earth pressure and the relative depth and the roughness of the pile shaft. In the proposed model, the concept of the critical depth is theoretically established, through a variable failure mechanism and the degree of shear mobilization along the pile-soil interface.

Key words: bearing capacity, pile, sand, shaft resistance, tip resistance, axisymmetric model, critical depth. (IGC: E1/E4)