Abstract: The bored piles 2.8 m in diameter and 120 m in length were adopted in the foundation of D13 frusta under a bridge.4-loop and U-size-grouting-pipe procedure was applied on two test piles,and static load tests were carried out on these two piles with the self-balanced load test method.Through collecting and dealing with the experimental data,some characteristics of load transfer mechanism and bearing behavior of bored pile,such as the relationship between load and settlement,the distribution of shaft friction,the relationship between pile-soil relative displacement and shaft friction,and tip resistance behavior were analyzed.It was indicated that,tip grouting could greatly decrease the disadvantageous construction influence,improve the load transfer mechanism of super-long bored pile,and greatly increase the stability of bearing behavior.