Hip Rigid Length Of The Pile Composite Foundation Bearing Behavior Research

Long-short-pile composite foundation is a new type of foundations developed in civil engineering of China in recent years. It brings into effect on decreasing settlement and adjusting the relation between Load-bearing capacity and deformation.It has been proved to be economical and better technical by engineering practices. Owing to complicated structures of Long-short-pile composite foundation, so far, completed design theory and calculation method haven't come into being. The development in theory drops behind practices evidently. Therefore, spreading the application and developing the technology of this new composite foundation is necessary to make a systemic research on bearing behaviours of the composite foundation.This paper presents a relatively complete analysis method based on composite foundation theories and pile foundation theories. The bearing behaviours of Long-short-pile composite foundation with static-pressed rigid pile are analyzed by field experimental study, dynamics calculation and finite-element method. The studies of the paper will gradually perfect and develop design theories and calculation methods of Long-short-pile composite foundation. The results are useful for practical engineering. Influencing factors and change laws of bearing behaviours of Long-short-pile composite foundation with static-pressed rigid pile are researched deeply by finite-element method numerical simulation and field static loading experiment and dynamics calculation. The results of both Long-short-pile composite foundation and Equilong-pile composite foudation are contrasted, the conclusions after calculation were shown as follows:1) In Long-short-pile composite foundation with static-pressed rigid pile, owing to additional loads, stress of pile and stress of soil are increasing linearly, and the former is bigger than the later. In the same geologic condition, stress of long pile increases more quickly than stress of short pile in Long-short-pile composite foundation. Pile-soil stress ratio of Long-short-pile composite foundation under rigid slab is bigger than that of Long-short-pile composite foundation under flexible slab.2) Settlement of Long-short-pile composite foundation with static-pressed rigid pile is smaller than short-pile composite foundation. In decreasing settlement and increasing load-bearing capacity, there is obvious technical superiority in Long-short-pile composite foundation with rigid pile.3) In Long-short-pile composite foundation with static-pressed rigid pile, both rigid slab and flexible slab bring into different effect on the integral behavior of composite foundation. Under rigid slab, the deformation of long pile is leading in settlement of composite foundation. Subsequently, there is harmonious deformation between short pile, soil and long pile. Load-bearing capacity of long pile is exerted fully. Under flexible slab, the deformation of composite soil composed of short pile and soil is leading in settlement of composite foundation. Subsequently, there is harmonious deformation between short pile, soil and long pile. In some extent, Load-bearing capacity of composite soil is exerted fully along with variation of loads.4) The stuck quanta of pile are increasing gradually by increasing loads. It makes more loads transfer to rigid pile. Owing to stuck quanta of pile, the pile-soil stress ratio is increasing in direct proportion.