Abstract:Based on the field testing data of 82 piles in 40 sites,through the study on the mobilization characteristics of pile total skin friction with pile head settlement,it is found that:(1) the total skin friction of 13 piles degrade in 36 piles whose total skin friction have arrived at ultimate state;(2) there are four types for pile total skin friction¢s degradation,i.e. the pile total skin friction keeps constant residual value,the pile total skin friction decreases continuously,the pile total skin friction increases slowly,and other type;(3) the pile head settlement when the total skin friction degrades for super-length pile is greater(21.34–35.21 mm),while the pile head settlement for short-middle length pile is smaller(4.13–14.19 mm);(4) the degradation of the pile total skin friction is induced by self-organization and self-adjustment of skin friction of all pile sections;(5) the Boltzmann model and three-beeline model can be used to describe different curves of the total skin friction with degradation versus the pile head settlement;and (6) some measures,such as improvement of the degree of roughness of pile surface,can be taken to prevent and prevent the accidents induced by the degradation of pile total skin friction. The following conclusion can be drawn that the research has important significance to the understanding of pile bearing characteristics.