均质土中端承壁板桩竖向振动特性

Vertical vibration characteristics of end-bearing barrette in homogeneous viscoelastic soil

为研究均质土中竖向简谐荷载作用下端承矩形壁板桩的振动特性,基于改进的Vlasov地基模型提出了壁板桩动力响应半解析计算方法.首先,将壁板桩土体视为连续体,提出了由轴向位移函数和水平衰减函数构成的位移模型.然后,利用哈密顿原理求得桩土体系的控制方程和动侧阻力表达式.最后,通过迭代算法计算动力响应.参数分析表明:相比圆桩,截面面积相同的壁板桩能显著提高桩顶静刚度和动刚度;当壁板桩横截面长宽比增大时,桩顶静刚度和动刚度均增大,且前者增幅较小而后者增幅较大;静态荷载下壁板桩轴力不受截面长宽比影响,动态荷载下则对其比较敏感;侧阻刚度在截断频率之前不受长宽比影响,但在截断频率之后,侧阻刚度随截面长宽比的增大而减小,且不受桩长细比的影响.

To study the vibration characteristics of an end-bearing rectangular barrette subjected to a time-harmonic vertical force in homogeneous soil,a semi-analytic calculation method for the dynamic response of the barrette was proposed based on the modified Vlasov foundation model.First,the barrette-soil was regarded as a continuum,and the displacement model composed of the displacement function along the barrette axis and the attenuation functions along the horizontal direction was proposed.Then,the governing equations of the barrette-soil system and the expressions of the vertical shaft resistance of the barrette were established according to Hamilton's principle.Finally,the dynamic responses were calculated by the iterative algorithm.Parametric analysis results show that barrettes have the larger barrette head stiffness for the static and dynamic loads than the circular piles with the same cross-sectional area.As the aspect ratio of the barrette cross section increases,both the static and the dynamic barrette head stiffness increase,and the increment of the static barrette head stiffness is less while that of the dynamic stiffness is larger.The axial force along the barrette axis for the static loads is independent on the aspect ratio of the cross section while the dynamic axial force is sensitive.The dynamic stiffness of the shaft resistance is not affected by the aspect ratio of the cross section below the cut-off frequency.However,beyond the cut-off frequency,it decreases with the increase of the aspect ratio and is insensitive to the variations in the slenderness ratio of the barrette.