可液化倾斜场地中桩基动力响应振动台试验研究

Shaking Table Test on the Dynamic Response of a PileFoundation in an Inclined Liquefiable Site

摘要:

为研究倾斜场地中桩基的动力响应，以2011年新西兰地震中受损的Dallington桥为原型，设计并完成可液化倾斜场地桥梁桩-土相互作用的振动台模型试验。试验再现了喷砂、冒水、地裂缝、场地流滑等宏观现象。试验结果表明，土层足够的液化势及惯性是造成倾斜场地侧向流滑的必要条件；浅层土相比深层土更易液化，液化层中的加速度由下至上呈现逐渐衰减的趋势，而未液化砂土层却表现为逐渐增大的特征；深部测点的桩侧土压力明显大于浅部测点，且土体的液化会弱化土对结构的压力；结构应变最大值位于上部桥台，而结构弯矩在桩身中部及土层分界面附近出现两个较大值，桩端嵌固及倾斜场地流滑是造成出现两个弯矩较大值的主要原因。

Abstract:

To study the dynamic response of pile foundations in inclined liquefiable sites, a series of shaking table model tests on the interaction of bridge pile-soil in sloping liquefiable sites were carried out, based on the Dallington Bridge damage in the New Zealand earthquake of 2011. Macroscopic phenomena such as soil liquefaction, ground cracks, and soil flow were reproduced. Results indicated that the liquefaction potential and inertia of the soil layer were necessary conditions for lateral spreading in the sloping site. Shallow soil was easier to liquefy than the deep soil, and the acceleration in the liquefaction layer gradually decreased from bottom to top, while that in the non-liquefaction layer showed an opposite characteristic. Lateral earth pressure around piles in deep soil is clearly greater than that in shallow soil, and soil liquefaction can weaken earth pressure on the pile structure. Maximum structural strain was located at the upper bridge abutment, while two large values of bending moment appeared in the middle of pile and the soil layer interface. The main reasons for the two large bending moments were the pile end embedding and soil flow at the inclined site.