Influence of pile toe type on bearing capacity of rock-socketed DPC piles

The drilling with pre-stressed concrete pile cased(DPC) pile is a new type of pre-drilled large-diameter PHC pipe pile, and its pile toe can be embedded in the moderately weathered rock. In order to reveal the influence of pile toe type on the bearing capacity of rock-socketed DPC piles, an ABAQUS finite element numerical analysis model was established by combining concrete damage plasticity model, interface bonding model and Mohr Coulomb model of equivalent Hoek Brown criterion. The influence factors such as hole bottom shape, pile shoe size and plugging concrete at the pile toe were emphatically analyzed. Numerical results show that, under the condition of no plugging concrete at the pile toe, the toe resistance ratio can reach more than 50% for the cylindrical cone groove at the bottom of the pile hole, and the influence of groove depth(15-30 cm) is limited. However, for the trapezoidal cone groove at the bottom, the end bearing capacity is obviously weakened, which is only 61% of that of cylindrical cone groove. The open-ended steel pile shoe can lead to the progressive destruction of the bedrock; the toe resistance ratio increases from 54% to 60%-76% when the thickness of pile shoe increases from 24 mm to 40-130 mm. Considering that increasing the thickness of pile shoe will affect soil discharge, the reasonable thickness of pile shoe should be determined by field tests. For the rock-socketed DPC pile with pile shoe, plugging concrete at the pile toe is an effective measure to improve the bearing capacity. However, the end bearing capacity will be weaken when there is sediment in the lower part of the plugging concrete. Finally, the improvement measures for the construction technology of DPC pile were put forward. © 2022, Science Press. All right reserved.