饱和土中大直径缺陷桩水平振动响应研究

为了研究成层饱和土中存在缺陷的大直径灌注桩的水平振动响应问题,基于Boit理论和严格的平面应变假设建立缺陷桩–饱和土横向耦合振动简化模型。引入势函数并利用算子分解法、分离变量法得到桩周饱和土对桩的水平作用力,再利用桩土接触面耦合条件及刚度矩阵传递法得到桩顶复阻抗;最后,通过模型对比与退化对比验证本文解的合理性。研究结果表明:(1)扩径对提高桩顶复阻抗起到的作用相对较小,但是缩径的出现将明显降低桩顶复阻抗;(2)桩顶动刚度和动阻尼对桩身缺陷大小和长度的敏感度不同,动刚度较动阻尼更为敏感;(3)桩顶附近缩径缺陷会导致桩顶复阻抗显著降低,而桩中部和端部附近缩径缺陷对桩顶复阻抗的影响相对较小。

Horizontal vibration response of defective large-diameter piles embedded in saturated soils

To investigate the horizontal dynamic response of defective large-diameter piles embedded in layered saturated soils,a horizontal coupling dynamic simplified model of the defective large-diameter pile-saturated soil is established based on Biot’s theory and strict plane strain assumptions.The potential function,operator decomposition method and variable separation method are introduced herein to obtain the horizontal force of the soil acting on the pile shaft,and then,the complex impedance of the pile top is derived by employing the coupling condition of the pile-soil contact interface and the stiffness matrix transfer method.The reliability of the obtained solution is verified by model comparison and degradation comparison.The results show that the enlarging segments of the pile contribute little to the increase of the complex impedance while the necking defects can significantly decrease the complex impedance.The dynamic stiffness of the pile top is more sensitive to the radius and length of the defect than the dynamic damping,and the necking defects near the pile head can more seriously reduce the complex impedance in comparison with those in the middle of the pile shaft or near the pile tip.