Drilled shafts in sand: failure pattern and tip resistance using numerical and analytical approaches

Drilled shafts are one of the most important types of pile foundations. Several researchers have suggested different soil failure patterns for driven piles; however, for drilled shafts, this issue is inadequately addressed in the literature. In this paper, a numerical approach was pursued to obtain the location and dimensions of plastic zones around the tip of drilled shafts. The dependence of the suggested failure pattern size on the soil properties and drilled shaft dimensions was investigated. Based on several analyses, a soil jug-shaped failure pattern around the tip of drilled shafts was proposed, and its dimensions were determined using the regression-based and trial and error analyses. A c Comparison of is made between the proposed failure pattern obtained in this study for drilled shafts with the ones reported in the literature that were based on the logarithmic spiral curve and also cavity expansion theory showed that. This study shows that the suggested failure pattern hasd some similarities with the one proposed based on the cavity expansion theory. Finally, based on the suggested plastic zone, an analytical approach was used introduced to estimate the tip resistance for drilled shafts in sand. Good agreement between the analytically predicted results and measured values of tip resistance reported in the literature was found.