（1 大连理工大学海岸与近海工程国家重点实验室， 大连 116024；2 大连理工大学建设工程学部水利工程学院工程抗震研究所， 大连 116024）

［摘要］为研究水平变刚度优化设计对桩筏基础动刚度的影响，针对成层地基上的大型桩筏基础，采用直接法计算桩筏基础模型在水平、竖直和回转三个方向上的动阻抗函数。对比分析了不同地震动水平下，变桩径和变桩距对桩筏基础动阻抗函数的影响。结果表明，水平变刚度优化设计和地震动水平对所研究桩筏基础动阻抗函数的影响随输入频率的变化而变化。当输入频率较小时，水平变刚度优化设计对桩筏基础三个方向动刚度的影响均不明显，当输入频率较大时，桩筏基础水平方向动刚度会减小，但竖向和回转方向的动刚度不受影响；地震动水平的增加会减小土体的等效剪切模量、增加土体的等效阻尼比，进而减小桩筏基础动阻抗函数曲线的振荡幅值。建议对桩筏基础进行不同输入荷载频率的研究，以确保优化设计的可靠性。

［关键词］桩筏基础；动阻抗；水平变刚度优化设计；变桩径；变桩距

中图分类号：TU473文献标识码：A文章编号：1002-848X(2021)06-0129-06

Influence of horizontal variable rigidity  optimization design on dynamic impedance of piled raft foundation

XIE Yunfei1,2, CHI Shichun1,2, WANG Maohua1,2

(1 State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China;2 Institute of Earthquake Engineering, Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian 116024, China)

Abstract:In order to study the influence of horizontal variable rigidity optimization design on dynamic stiffness of pile raft foundation，for large piled raft foundation in layered soils, the direct method was used to calculate the dynamic impedance function of the piled raft foundation model in three directions of horizontal, vertical and rotational directions. The influence of optimization design with variable pile diameter and variable pile spacing on the dynamic impedance function of the piled raft foundation under different earthquake ground motions was analyzed. The results show that the influence of horizontal variable rigidity optimization design and ground motion level on the dynamic impedance function of piled raft foundation varies with the change of input frequency. When the input frequency is small, the influence of the horizontal variable rigidity  optimization design on the dynamic rigidity  of pile raft foundation in three directions is not obvious. When the input frequency is large, the horizontal dynamic rigidity  of pile raft foundation decreases, but the vertical and rocking dynamic rigidity  is not affected. The increase of  ground motion level can reduce the equivalent shear modulus of the soil and increase the equivalent damping ratio of the soil，which reduce the oscillation amplitude of the dynamic impedance function curve of the piled raft foundation. It is suggested that it is necessary to study the different input load frequencies of pile raft foundation in order to ensure the reliability of optimization design.

Keywords:pile raft foundation;dynamic impedance;horizontal variable rigidity  optimization design;variable pile diameter;variable pile spacing

作者简介：谢芸菲，博士研究生，Email：xieyunfei@mail.dlut.edu.cn。