Abstract: The decrease of pile’s skin friction of super-long pile is a common phenomenon. In this study, a new hyperbolic load transfer model which includes the stage of decrease of pile’s skin friction is proposed. The characteristics of nonlinear and decrease of the interaction of pile and soil is fully considered in this model. Furthermore, a UMAT subprogram is compiled in FORTRAN on the basis of the new model. Based on a history case, a comparison among situ data, the results calculated by the origin contact analysis in ABAQUS and the results adopting the procedure developed in this paper. It is shown that, 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 are more consistent with field test data. It is proved that by adopting the load transfer model in this paper, the nonlinear characteristic and decrease of pile’s skin friction is well simulated of the interaction of pile and soil. Also, the estimation of the capacity of the pile is more reliable.

Key words: load transfer model, decrease of skin friction, secondary development of program