Dynamic response of open pipe pile under vertical cyclic loading in sand and clay

摘要

The bearing capacity of a pile under vertical cyclic loading is one of key factor in the design of pile foundation. In this study, an innovative large-scale model test of double-wall open-ended pipe pile was conducted to investigate the cyclic bearing characteristics of open-ended pipe pile under various soil conditions and load frequencies. The experimental results show that the ultimate bearing capacity of piles in sand is much larger than that in clay. Under cyclic loading, the cumulative settlement in clay was found to be larger than that in sand, which was clearly indicated by clear increasing and stabilizing trends. Furthermore, the external friction of pipe pile in sand changes in an oblique "V" shape with depth, whereas that of the pipe pile in clay is inclined "W". With increase in number of cycles, the external friction of upper part of the pipe pile and the internal friction of lower part of the pipe pile in sand decrease first and then tend to be stabilize. On the other hand, the external friction of upper and middle parts of pipe pile and internal friction of lower part of pipe pile in clay observed to have the same trend. Contrarily, the external friction in the middle of pipe pile in sand is an opposite trend. Moreover, the load frequency of dynamic cycle loading tends to have a great influence on the friction resistance, and this influence is more significant in clay than that in sand.