Abstract: Tapered rigid core composite cement-soil pile is an emerging type of composite pile. In order to investigate its bearing behavior in engineering applications such as highways and railways under long-term cyclic loading, model tests were conducted on four composite piles with different pile core wedge angles, static loading ratios and cyclic loading ratios. The ultimate bearing capacity under static loading as well as the cumulative settlement, pile axial force distribution, tip resistance and side friction resistance were evaluated. The results indicated that the bearing capacity of tapered inner core composite piles under static loading was better than that of constant cross-section inner core composite piles. The cumulative settlement of composite piles increased with the increase of static loading ratio and cyclic loading ratio, and can be classified into three types of stability, development and failure under different combinations of dynamic and static loading. At the same time, the value range of load satisfying each type was also given. The interaction between the core pile and the cement-soil outer pile was not noticeably diminished, and the composite pile with a tapered core pile could fully mobilize the side friction resistance of the upper soil around the pile sides and effectively reduce the stress concentration at the tip of the core pile. Therefore, its ability to resist cyclic loading was better than that of the composite pile with a constant cross-section core pile.

Key words: tapered rigid core composite cement-soil pile, cyclic loading, ultimate bearing capacity, cumulative settlement, pile stress