滞回阻尼土中大直径管桩纵向振动响应解析解

ANALYTICAL SOLUTION OF VERTICAL VIBRATION RESPONSE OF LARGE DIAMETER PIPE PILE IN HYSTERETIC DAMPING SOIL

考虑土体材料的滞回阻尼和桩周土–桩–桩芯土耦合振动,对黏弹性地基中现浇大直径管桩纵向振动频域特性进行理论研究。假定桩为一维杆,土体为轴对称均匀黏弹性体。采用Laplace变换和分离变量的方法求得桩周土和桩芯土纵向位移频域解,然后利用桩土位移和应力连续耦合条件求得桩顶频域响应解析解。将所得解完全退化到实心桩的解,验证解析解的合理性。分析桩长、土体剪切模量和桩径对桩顶复刚度的影响,得到各参数对桩振动特性影响的规律。分析表明:桩长增大,桩顶复刚度的振荡幅值和共振频率均显著减小,但当桩长增大到一定桩长的时候,增加桩长基本没有影响。土体剪切模量越大,桩顶复刚度的振荡幅度越小,且桩周土剪切模量的影响比桩芯土更为显著。外径的增大或内径的减小,均会使桩顶复刚度的振荡幅值增大。

Considering the hysteretic damping of soil and coupled vibration between pile,outer and inner soil,the frequency-domain vertical vibration response of cast-in-place concrete large diameter pipe pile in viscoelastic soil is investigated. The pile and the soil are treated as one-dimensional rod and axisymmetric viscoelastic medium, respectively. The frequency domain solutions of outer and inner soil are obtained by Laplace transformation technique and separation of variables method. The dynamic response of pile is then obtained based on the continuity assumption of displacement and stress between pile and outer soil as well as inner soil. The solution is compared with that of solid pile to verify its rationality. Moreover,by analyzing the effects of pile length,shear modulus of soil and pile radii on the complex stiffness of pile,the regularity of variations of vibration characteristic with parameters is obtained. Analysis shows that the oscillation amplitudes and resonance frequencies of complex impedance of pile decrease with the increasing pile length,but when pile length increases to a critical length,the effect tends to vanish;the oscillation amplitudes of complex impedance decrease with the increasing shear modulus of soil,and the effect of shear modulus of outer soil is larger than that of inner soil; the oscillation amplitudes of complex impedance increase with the increasing outer radius or decreasing inner radius.