Abstract：The accumulation rule of pile-head displacement plays a vital role in the settlement-control of the piled-embankment of highways and high-speed railways. In this study, axial cyclic loading tests were carried out on two 29.5m-long pre-stressed concrete pipe piles installed in soft clay in Huzhou, China, which were subjected to various combinations of static loading and cyclic loading, so that the ultimate capacity and the pile-head accumulated settlement characteristics were investigated. The test results indicated that the development of the long-term accumulated settlement can be categorized into three patterns: quickly stabilized (QS), progressively developing (PD), and dramatically failed (DF). When the cyclic load ratio (CLR, the ratio of the cyclic load amplitude to the ultimate capacity which is defined to describe the loading characteristics) is less than 0.2, the pile-head accumulated settlement tends to be stabilized (independent of the number of cycles). When 0.2<CLR≤0.5, the pile-head accumulated settlement increases gradually with the number of cycles without reaching failure. When CLR is larger than 0.5, the remarkable accumulated settlement is developed with the number of cycles, and the plunging failure can be observed in the semilog coordinates. Furthermore, the effect of the static and cyclic loading level on the pile-head accumulated settlement is analyzed. Finally, some suggestions for the engineering design of piles in soft clay under long-term cyclic loading are given.
