Abstract:Parameters of dynamic test are obtained from the analysis of pile foundation of small-span bridge for high-speed railway;and these parameters have been used in dynamic tests on bored piles in soft soil. Research is accomplished on amplitude of dynamic displacement,settlement at top of pile,axial force distribution of pile shaft,dynamic side resistance,axial stiffness of single pile and bearing capacity of piles under long-term cyclic loading. With the increasing of cyclic loading times,the results indicate that:(1) shaft force distribution of bored pile is different from that of original cases under long-term cyclic loading;and this difference mainly concentrates on top of 1/3 pile length;(2) enhancing effect of dynamic side resistance and degradation effect of dynamic side resistance are obtained in sand soil;(3) ultimate bearing capacity of single pile changes very small under the testing conditions;and (4) cyclic loading can induce decreasing of axial stiffness of single pile.