The analysis model of shaft resistance softening of a new type of static drill rooted super-long nodular pile

Abstract

The static drill rooted nodular pile is a new type of pile foundation which consists of precast nodular pile and the cemented soil along the pile shaft. The pile foundation not only reduces the compacting effects and mud pollution, but also combines the advantages of the relatively high skin friction of the cemented soil and the higher strength of the precast pile. As the mechanism of the shaft resistance softening of such super-long piles is not clear, existing general finite element software can not reflect the softening of soil. Therefore, a new hyperbolic load transfer model considering the shaft resistance softening is proposed in this paper and corresponding UMAT subprogram is developed in FORTRAN language, which forms the integration model of load transfer model and subprogram. The curves of Q-s relationship of pile’s top, the distribution of pile’s skin friction and the relationship of pile’s skin friction versus pile-soil relative movement calculated by the proposed model are highly consistent with the field test data. In this paper, the mechanical behavior can be calculated by the proposed model accurately and effectively. At the same time, this new type of static drilling rooted nodular pile can make the bearing capacity of super long piles to be mobilized effectively.