液化土中对称双斜桩动力反应特征及p-y曲线规律试验研究

地震作用下液化土中桩基动力反应一直是岩土工程抗震研究的热点问题，基于非液化土和饱和砂土中对称双直桩和对称双斜桩电磁式振动台试验，在试验中输入不同地震动强度的正弦波和El-Centro地震波，对比研究非液化土和饱和砂土中，直、斜桩水平动力反应特征、桩身弯矩分布及p-y滞回曲线规律。试验研究结果表明：(1) 无论是正弦波输入还是El-Centro地震波输入试验，随着加速度峰值的增加，斜桩承台加速度和位移反应放大值均低于相同工况下的直桩基础，尤其在砂土液化时斜桩的水平抗震性能表现更好；(2) 在非液化砂土中，斜桩和直桩弯矩均较小，而当饱和砂土发生液化后，斜桩的最大弯矩是直桩3倍左右，桩顶和距离桩端0.16 m处，直桩的最大弯矩则主要集中在桩顶与承台连接处；(3) 斜桩p-y曲线包络面积更大，利于能量耗散，在非液化砂土中斜桩p-y滞回曲线整体斜率低于直桩，在饱和砂土中其整体斜率则高于直桩。因此，在进行液化土中桩基抗震设计时，斜桩的整体性能优于直桩基础，但在设计时应增强斜桩桩身的局部抗弯刚度以抵抗较大的弯矩作用。研究成果对可液化土层中工程斜桩抗震设计理论具有重要的参考价值。

Dynamic response and p-y curve of symmetric inclined piles in liquefied soil

The dynamic response of pile foundation in liquefied soil under earthquake has always been a hot issue in the geotechnical engineering. This paper presents the results of the electromagnetic shaking table test on the symmetric double vertical piles and the symmetric double inclined piles in non-liquefied soil and saturated sand. The sinusoidal waves of different earthquake intensities and the El-Centro seismic wave were applied in the tests. The comparsion between the results for two types of piles was made. Under either the sinusoidal wave or the El-Centro seismic wave，when the peakacceleration increases，the acceleration at pile cap and the amplified displacement of inclined piles are lower than those of vertical piles under the same working conditions. The inclined piles resist thehorizontal earthquakebetter than vertical pile especially whensandis liquified. The inclined piles and vertical piles have the smaller bending moments in the non-liquefied sand. But when the saturatedsand is liquefied，the maximum bending moment of the inclinedpiles is located on the pile cap and at the place of 0.16 m away from the pile tipand is about three times as much as that of the vertical pile，which is mostlylocated at the connection of the pile and the pile cap. The enclosedarea of hysteretic p-y curves of inclined piles is larger，which is better for thedissipation of energy. Theoverall slope ofhysteretic p-y curves of inclinedpiles is lower in non-liquefied sandbut higher in saturated sandthan ones of vertical piles. Therefore，the overall performance of inclinedpiles is better than vertical piles，but the local flexural rigidity of inclinedpiles should be increased to resist the larger bending moment.