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为研究桥梁群桩基础的大质量承台和外露桩基对桩-土动力相互作用效应的影响,分别对低承台(与土接触)和高承台群桩基础进行了离心振动台模型试验。试验中地基土采用了黏质粉土,上部结构简化为质点和杆构件,基础形式包括单桩和群桩。为模拟地震剪切波作用下土层运动效应,采用叠环式层状剪切箱实现土体的层状自由剪切,箱内壁设置橡胶膜以消除边界反射效应。在加速度为50g的离心环境中,选取Chi-Chi地震波作为基底激励输入,在不同输入峰值加速度下,分析了结构-群桩基础的地震响应。试验结果表明:与低承台群桩基础相比,高承台形成的群桩外露会增加上部结构和承台的惯性效应,改变桩身峰值弯矩的分布,表现为承台与桩接触处的桩身峰值弯矩下降,但桩身最大峰值弯矩改变较小。
In order to study the effect of pile cap-soil dynamic interaction effect between large pile foundation and exposed pile foundation of bridge group pile foundation, centrifugal shaker model tests were carried out for pile foundation with low cap (contact with soil) and pile cap group. In the experiment, clayey silt was used as the foundation soil, the upper structure was simplified as the mass point and the rod structure, and the basic forms included single pile and group pile. In order to simulate the effect of soil movement under shear wave, a laminated layered shearing box is used to realize the free shear of layered soil. A rubber membrane is set on the inner wall of the tank to eliminate the boundary reflection effect. In a centrifugal environment with an acceleration of 50g, the Chi-Chi seismic wave is selected as the base excitation input, and the seismic response of the structural-group pile foundation is analyzed under different input peak accelerations. The experimental results show that, compared with the low cap group pile foundation, the exposed pile groups formed by the high cap pile increase the inertial effect of the superstructure and cap, and change the distribution of peak bending moment of the pile body, as shown in the pile Body peak bending moment decreased, but the maximum peak bending moment changed little.