不同厚度饱和砂土中群桩P-Y滞回曲线规律研究

根据Buckingham π定理设计制作直群桩和斜群桩相似模型，通过电磁式振动台试验方法，分别考虑非液化砂土、300 mm和380 mm两种不同厚度饱和砂土，开展在规则正弦波输入下桩土相互作用P-Y滞回曲线规律研究。结果表明:在非液化砂土中，P-Y滞回曲线的主斜率变化较小，说明在振动输入过程中，桩周土体刚度并未发生显著的降低；在两种不同厚度的饱和砂土试验过程中，P-Y滞回曲线主斜率在振动输入初期较大，随着振动输入时长增加呈现出不断下降的趋势，桩侧土体的刚度逐渐减小；桩身横向受力特性受埋置深度的影响，随着埋深的增加，桩身受到的侧向力逐渐减小，而桩-土相对位移则逐渐增大；直群桩的侧向力、位移峰值以及P-Y滞回曲线包络面积远大于斜群桩，说明直群桩在振动过程中的耗能要高于斜群桩；在厚度较大的饱和砂土中，群桩P-Y滞回曲线的包络面积增大，表明桩土相互作用过程中滞回耗能增加，P-Y滞回曲线主斜率减小，桩侧土体刚度减小。本文研究成果为可液化土中的桩基抗震理论提供参考。

Research on P-Y hysteresis curve regularity of group piles in saturated sand with different thickness

According to Buckingham theorem，the straight pile group and inclined pile group similarity models were designed and made. By means of electromagnetic shaking table test method，considering the non-liquefied sand， 300mm and 380mm saturated sands with different thicknesses，the study of the P-Y hysteresis curve of the pile-soil interaction under the input of regular sine waves is carried out.The results show that in non-liquefied soil，the main slope of the P-Y hysteresis curve has little changes，which indicate that the stiffness of the soil around the pile does not change significantly during the vibration process. In two kinds of saturated sands with different thicknesses，the main slope of the hysteresis curve of P-Y is larger in the initial stage of vibration，and it shows a decreasing trend with the continuous input of sine waves. The stiffness gradually decreases；the lateral force characteristics of the pile are affected by the embedment depth. As the depth of the pile increases，the lateral force on the pile body gradually decreases，while the pile-soil relative displacement gradually increases；The lateral force，displacement peak and envelope area of the pile P-Y hysteresis curve are much larger than those of the inclined group piles，which indicates that the energy consumption of the straight group piles is much higher than that of the inclined group piles. The inclined group piles have a reducing effect on the lateral load；As the thickness of the saturated sand increases， the envelope area of the P-Y curve increases，indicating that the energy consumption of the pile increases，and the lateral dynamic response of the pile becomes more significant. At the same time，the main slope of the P-Y curve decreases and the stiffness of the soil on the side of the pile decreases.