强震作用下液化场地桩-土非线性动力相互作用特性

为研究强震作用下液化场地桩-土非线性动力相互作用特性,依托海文大桥实体工程,利用Midas/GTS有限元软件,建立了桩-土相互作用模型,分析了地震动峰值为0.35g时4种类型地震波作用下桩身加速度、桩身位移、桩身弯矩及剪力等动力响应,并根据计算结果对桩基在强震作用下的安全进行了评价.结果表明:在0～10 m的可液化粉细砂层,桩身加速度峰值迅速增加,并在桩顶处达到最大,桩顶加速度出现峰值的时刻与桩底相比均呈现滞后现象,最大滞后时间为2.14 s;不同类型地震波作用下,在可液化的粉细砂层,Kobe波产生的桩顶位移最大,El-Centro波次之,5010波产生的桩顶位移最小;桩身弯矩峰值均出现在液化层和非液化层分界处,桩身剪力峰值均出现在地下0～10 m的可液化土层之间,Kobe波作用时,桩身弯矩和剪力峰值均最大,El-Centro波次之,5010波最小;地震动强度为0.35g,5010、5002、El-Centro地震波作用时,桩身弯矩及剪力峰值均未超过桩身截面抗弯和抗剪承载力,Kobe地震波作用时,桩身弯矩峰值小于桩身截面抗弯承载力,而桩身剪力峰值超出桩身截面抗剪承载力的68.6％,桩基础桩身强度不满足抗震要求,建议增加桩基础纵向配筋.

Nonlinear dynamic interaction characteristics of pile-soil in liquefaction site under strong earthquake

In order to study the nonlinear dynamic interaction characteristics of pile-soil in liquefaction site under strong earthquake, a pile-soil interaction model is established based on the solid project of Haiwen Bridge and Midas/GTS finite element software. The dynamic responses of pile acceleration, pile displacement, pile bending moment and shear force under four types of seismic waves with ground motion peak of 0.35g are analyzed, and the safety of pile foundation under strong earthquake is evaluated according to the calculation results. The results show that the peak acceleration of the pile increases rapidly and reaches the maximum at the pile top in the liquefied silty sand layer of 0~10m. The peak acceleration at the pile top show a lag compared with the peak acceleration at the bottom of the pile, and the maximum lag time is 2.14 s; Under the action of different types of seismic waves, the displacement of the pile increases rapidly in the liquefied silty sand layer, Kobe wave produces the maximum pile top displacement, followed by the El-Centro wave, 5010 wave produces the minimum pile top displacement; The peak bending moment of the pile appears at the position of 10m underground, that is the boundary between the liquefied soil layer and the non-liquefied soil layer, and the peak shear force of the pile appears between the liquefiable soil layer of 0~10m underground. The peak value of pile bending moment and shear force is the highest under the action of Kobe wave, the peak value of bending moment and shear force of pile body under the action of 5002 wave is less than that of El-Centro wave, and the peak value of pile bending moment and shear force is the minimum under the action of 5002 wave; When the seismic dynamic strength is 0.35g, and under the action of 5010, 5002 and El-Centro seismic waves, the peak bending moment and shear force of the pile do not exceed the bending and shear bearing capacity of the pile section. Under the action of Kobe seismic wave, the peak bending moment of the pile is less than the bending bearing capacity of the pile body section, while the peak shear force of the pile body exceeds 68.6% of the shear bearing capacity of the pile body section. The pile foundation pile strength does not meet the anti-seismic requirements, so it is suggested to increase the longitudinal reinforcement of the pile foundation.