径向非均质黏性阻尼土中管桩纵向振动特性

为分析施工扰动对管桩纵向振动特性的影响,发展建立了基于复刚度传递径向多圈层平面应变模型黏性阻尼土中管桩-土体纵向耦合振动模型.利用拉普拉斯变换和径向复刚度传递,得到桩芯土与桩身界面处的复刚度,并利用桩土界面上位移连续、力平衡条件推导得出桩顶动力阻抗的解析解,通过进一步参数化分析分别探讨桩长径比、桩内外径比、桩身弹性模量、土体黏性阻尼系数、桩周土施工扰动程度和扰动范围对桩顶纵向振动特性的影响规律.结果表明:管桩桩长增加使得桩顶动力阻抗曲线振幅和共振频率降低;桩芯土体对桩体可以起到减震作用;桩顶动刚度和动阻尼曲线振幅随施工引起桩周土软(硬)化程度增加而减小(增大);管桩桩顶动力阻抗振幅水平随施工扰动引起桩周土体软(硬)范围增加而增大(减小),此种影响仅在近桩小范围内较为明显,超出该范围即大幅衰减至稳定;当施工扰动较明显时,在管桩纵向振动特性分析中宜考虑此种桩周土体径向非均质性的影响.

Dynamic impedance of vertical vibration of pipe pile embedded in radially inhomogeneous viscoelastic soil

To investigate the effect of construction disturbance on vertical vibration characteristics of pipe pile, a simplified mechanical model of vertical vibration for pipe pile embedded in radially inhomogeneous soil was proposed by employing the viscous damping model and considering pipe pile as uniform cross-section and elasticity based on the plane stain model of annular complex stiffness transfer. Firstly, based on Laplace and complex stiffness transfer method, the composite stiffness of pile-soil interface was derived. Secondly, the frequency domain analytical solution of pile head dynamic impedance was obtained by using the compatibility condition. Finally, effects of the slenderness ratio of pile, the inner and outer diameters of pile, the elastic modulus of pile, the viscous coefficient of soil, and the construction disturbance intensity and range on the complex impedance at the pile head were analyzed. The results showed that the amplitude and resonance frequency of complex impedance at the pile head decreased with the increase of slenderness ratio of pile; the inner soil attenuated vertical vibration of pipe pile to a certain extent; the more the softening (hardening) intensity of the surrounding soil was, the lower (higher) the amplitude of complex impedance became; the amplitude of complex impedance at the pile head increased (decreased) with the enlargement of softening (hardening) range due to construction disturbance. It is suggested that the radial inhomogeneity should be considered in the analysis of vertical vibration for pipe pile when the construction disturbance is distinct.