高速铁路桥桩在轴向循环荷载长期作用下的承载和变形特性试验研究

DYNAMIC BEHAVIORS OF PILE FOUNDATION OF HIGH-SPEED RAILWAY BRIDGE UNDER LONG-TERM CYCLIC LOADING IN SOFT SOIL

针对高速列车通过小跨度桥梁时列车活载对桥桩的影响分析来获得动力加载参数,进而对位于软粘土地层中的钻孔灌注桩进行了轴向循环荷载长期作用下的动力试验,测试和研究了循环荷载长期作用下桩的动位移幅值、桩顶沉降、桩身轴力、桩侧动摩阻力和单桩极限承载力等参数的发挥和变化情况。试验结果表明:列车循环荷载长期作用下,灌注桩的桩身轴力发生了局部调整,砂性土层的桩侧摩阻力具有增强效应,淤泥质粘性土的桩侧摩阻力具有退化效应;列车循环荷载对软土地区单桩的承载能力和桩基的工后沉降影响甚微,但会使单桩竖向刚度降低。

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.