不同厚度饱和砂土中群桩结构动力响应试验研究

Experimental Study on the Dynamic Response of Pile-group Structure in Saturated Sand with Different Thicknesses

液化土中桩基础动力响应规律一直是工程抗震领域关注的热点问题。本文基于非液化砂土和不同厚度饱和砂土中的2×2群桩结构模型振动台试验,通过输入一定峰值加速度和频率的正弦波,对群桩在非液化土层和两种不同厚度饱和砂土层中的横向动力响应特性进行振动台试验研究。研究结果表明:在正弦波输入情况下,非液化砂土中群桩承台加速度和位移时程与台面输入时程相比,波形变化规律与峰值大小均相差不大;而对两种不同厚度饱和砂土中承台加速度和位移峰值放大较多,在相对较薄的饱和砂土中群桩承台加速度峰值较台面输入放大了1.83倍,较台面输出位移峰值放大了1.58倍;在相对较厚的饱和砂土中承台加速度和位移峰值则分别放大了2.18倍和1.91倍,说明在相同输入条件下,较厚的饱和砂土在发生液化后群桩承台的动力响应更加显著。

The dynamic response law of pile foundations on liquefied soil is a perennial hot topic in the field of earthquake resistance engineering.In this work,the lateral dynamic response characteristics of pile groups in a nonliquefied soil layer and saturated sand layers with two different thicknesses are studied under the input of a sine wave with a certain peak acceleration and frequency through the model shaking table tests of 2×2 pile groups.Results show that under the input of the sine wave,the time histories of acceleration and displacement at the pile cap in nonliquefied sand are not significantly different from those of the input.The peak acceleration and peak displacement at the pile cap drastically increase in saturated sand with two different thicknesses.Specifically,the peak acceleration and peak displacement at the pile cap are magnified by 1.83 and 1.58 orders,respectively,in thin saturated sand,and by 2.18 and 1.91 orders,respectively,in thick saturated sand.Under the same input condition after liquefaction,the dynamic response of the pile cap is more remarkable in thick saturated sand than that in thin saturated sand.