Vertical bearing capacity of tapered piles in sands using cavity expansion theory

Abstract

On the basis of the mechanism of tapered piles and evidence obtained from small scale model tests, this paper proposes cylindrical and spherical cavity expansion theories to evaluate the skin friction by introducing a stress–dilatancy relationship, as well as the end bearing capacity of tapered piles by introducing a tapering factor. In general, in order to evaluate the skin friction, either the angle of internal friction or dilatancy angle is assumed to be constant. This research improves on this drawback and considers both properties to calculate the skin friction through an iterative process in the load transfer method. At the mean time, the effect of angle of tapering is introduced to evaluate the end bearing capacity of tapered piles. The test results and proposed models show that a slight increase in the tapering angle of the pile results in higher skin friction and affects the end bearing resistance compared with conventional straight piles on different types of sands at different relative densities. The proposed models are then applied to different types of prototype and real type pile tests in order to evaluate the predicted skin friction, expected end bearing capacity and vertical bearing capacity.