Improved Calculation Method of Super-Long Pile in Deep Soft Soil Area

Abstract

The exertion of super-long pile skin friction is an asynchronous process in deep soft soil area. The limitation of skin friction on the upper part of pile is much smaller than the lower part of pile. The softening of super-long pile skin friction is also a common phenomenon. Therefore, a new hyperbolic load transfer model is proposed in this paper, which takes into account the softening of pile skin friction and the nonlinear characteristic of pile–soil relative displacement. Meanwhile, a User-Defined Material (UMAT) subroutine is written in FORTRAN language and connected with an ABAQUS interface. The curve of pile skin friction is obtained, which is more consistent with practical engineering. It is further developed into a universally applicable function of super-long piles. The settlement and effective pile length in deep soft soil area can be calculated by a new function with the consideration of super-long pile weight. Example analysis shows that the calculation of axial force distribution of super-long pile, settlement of pile top, and effective pile length are more consistent with pile test results. In summary, the method proposed in this paper can exactly reflect the working characters of super-long pile in practical engineering, which can provide valuable reference for the design of super-long pile.