NUMERICAL NONLINEAR ANALYSIS ON NEGATIVE SKIN FRICTION BEHAVIOR OF SINGLE PILE UNDER SURFACE LOADS

Three dimensional nonlinear analyses on negative skin friction of a single pile was carried out for a specific case under surface loads. The results show the similarities and differences of negative skin friction behavior between friction pile and end-bearing pile. It was found that loading velocity of surface loads and the pile working loads influences negative skin friction very much: the more the loading velocity,the less the negative skin friction; the dragload of a pile without pile axial load is the ultimate value and could be considered as an upper limit for conventional analysis. Moreover,combinations of pile working load with surface load lead to change the pile axial force,namely,application of the working load and then application of the surface load caused a maximal negative skin friction,and on the contrary case minimum.