Mechanical and numerical behavior of water jet-driven under-reamed concrete piles

Water jet-driving technique has been shown as a viable practice for driving prefabricated piles in resistant soil layers. However, this technique is also associated with the reduction of load capacity of piles. Along these lines, the use of reams in prefabricated concrete piles improves their mechanical performance. The main objective of this research was to study the efficiency of reams on water jet-driven concrete piles; to this extent, pile loading tests and mini-cone tests were carried out before and after the driving of the piles. In addition, numerical modelling with the finite element method (FEM) was applied to study the stress-strain behavior. By means of the numerical modelling, it was possible to identify the stress and strain distribution at the tip, shaft, and reams of the piles; this allowed the understanding of the contribution of these elements in the total load capacity. Results have shown that the reams directly contribute for load capacity, with increases up to 40% when compared to conventional piles. Laboratory tests and numerical modeling proved to be fundamental tools to understand the mechanisms behind the contribution of reams to the load capacity of piles.