基于P波斜入射海相软土区螺旋桩动力响应分析

Dynamic response analysis of helical piles in marine soft soil areas based on P-wave oblique incidence

在地震频发地区,越来越多建筑使用螺旋桩作为基础,此桩型具有良好的抗震能力。通过建立三维有限元模型,基于黏弹性人工边界,把地震作用等效为边界结点上的作用力。该研究考虑动静边界转换的影响,最后建立了具有黏弹性边界的螺旋桩-土体三维模型。探讨了处于海相软土场地下,不同种类地震波、地震强度、入射角度和螺旋叶片个数对螺旋桩轴力、弯矩和动力p-y曲线的影响。结果表明,相比较于弯矩,入射角度对轴力和动力p-y曲线的影响较大。除此之外,地震强度对弯矩的影响较大,而地震波频率和螺旋叶片个数对其影响较小。不同地面峰值加速度(0.05g,0.10g,0.30g)时,随着入射角度的改变,螺旋桩受到最大和最小弯矩的差值从144.1 N·m增加到了891 N·m。通过该研究结论,不仅可以得出软土场地下螺旋桩-土体的相互作用关系,也能为螺旋桩抗震设计提供依据。

In earthquake-prone areas,more and more buildings are using helical piles as foundations,they have good aseismic ability.By establishing a 3-D finite element(FE)model and using viscoelastic artificial boundaries,seismic actions are equivalent to forces acting on boundary nodes.Here,considering effects of dynamic-static boundary conversion,the helical pile-soil body 3-D FE model with viscoelastic boundaries was established.Effects of different types of seismic waves,seismic intensity,incidence angle and number of spiral blades on axial force,bending moment and dynamic p-y curve of helical piles located underground in marine soft soil site were explored.The results showed that compared to bending moment,incident angle has a larger impact on axial force and dynamic p-y curve;seismic intensity has a larger impact on bending moment,while seismic wave frequency and number of spiral blades have a smaller impact on bending moment;under different PGAs of 0.05 g,0.10g and 0.30 g,the difference between the maximum and minimum bending moments of helical pile increases from 144.1 Nm to 891 Nm with variation of incident angle;the study results can not only obtain interaction relation of underground helical pile-soil body in soft soil site,but also provide a basis for aseismic design of helical piles.