Abstract: Based on the comparison of the long-term settlement measurement data of driven pile foundation of twenty-five high rise buildings, the effects of composite of pile toe compressible layer and soil property surrounding the pile shaft on long-term settlement characteristics of driven pile foundation are studied and the results show the effects on settlement behaviors of driven pile foundation induced by thick sand layer existing in the shallow of pile shaft are very relevant to the compressive soil layers underlying the pile tip. The function of thick sand layer of pile shaft to decrease the pile foundation settlements and improve the settlement behaviors is remarkable when the compressive soil layers are mainly composed by quasi-sand layers; namely the quasi-sand ratio β more than 75 percent whereas the function is disappeared when the quasi-sand ratio β is less than 50 percent. The concept of component of compressive layers mainly functioned on the pile foundation settlement behaviors is ordinary existed in the case of the existed of thick sand layer surrounding the pile shaft. The results above mentioned are strictly related to the complex construction action induced by the construction of displacement pile.

Key words: driven pile, quasi-sand ratio, long-term settlement, sand, construction action, cohesive soil