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为研究沉管隧道基槽边坡的动力特性,以在建的港珠澳大桥沉管隧道工程为背景,设计并完成了几何比尺1∶60的沉管隧道基槽变坡度边坡大型振动台模型试验,并对试验模型的动力特性进行了分析。针对试验设计的细节尤其是相似关系设计和模型土设计进行了重点介绍。基于Buckingham-π相似原理,通过量纲分析的方法得到了相似关系控制方程,并以此方程为基础推导得到了试验所需各物理量的动力相似关系;利用锯末和砂按照一定比例混合配制模型土,通过一系列室内动三轴试验研究了模型土与原状土动力的特性,找到了动力特性与原状土相匹配的模型土;根据实际工程的场地状况和振动台试验设备的要求,设计并制作了长、宽、高分别为4.5,4.0,1.2m的刚性模型箱。通过振动台试验研究了输入不同频谱、峰值加速度和频率相似比地震波的变坡度场地地震响应差异,探讨了边坡的动力响应规律。试验验证了模型箱边界效应,边界处土体的加速度响应与中间处土体基本一致,并与其他试验结果进行了对比。结果表明:土体对输入的地震波具有明显的放大作用;不同频谱地震波作用下,边坡坡面的加速度响应具有明显的差异;不同地震动峰值加速度输入条件下,峰值加速度(PGA)放大系数沿坡面分布规律基本一致;不同频率的地震波作用下,变坡度PGA放大系数随频率相似比的增大而增大。
In order to study the dynamic characteristics of the base slope of immersed tunnel, taking the immersed tunnel project of Hong Kong-Zhuhai-Macau Bridge under construction as a background, a large-scale vibration Taiwan model test, and the dynamic characteristics of the test model were analyzed. The details of the experimental design, especially the similarity relation design and the model soil design, are mainly introduced. Based on the Buckingham-π similarity principle, the similarity relational control equation is obtained by the method of dimensional analysis. Based on this equation, the dynamic similarity of the physical quantities required for the test is derived. The model soil is prepared by mixing sawdust and sand according to a certain proportion , The dynamic characteristics of model soil and undisturbed soil were studied through a series of indoor dynamic triaxial tests, and the model soil with dynamic characteristics matching the undisturbed soil was found. According to the site condition of the actual project and the requirements of the shaking table test equipment, the design and manufacture A long, wide, high, respectively, 4.5,4.0,1.2 m rigid model box. The shaking table test is used to study the difference of seismic response of the sloped field with different frequency spectrum, peak acceleration and frequency similar to the seismic wave, and the dynamic response of the slope is discussed. Experiments verify the boundary effect of the model box. The acceleration response of the soil at the boundary is basically consistent with that of the soil in the middle, and is compared with other test results. The results show that the soil has a significant amplification effect on the input seismic waves. The acceleration responses of the slope have obvious differences under the different spectral seismic waves. Under the condition of different peak ground acceleration input, the peak acceleration (PGA) The slope distribution is basically the same; under the action of different frequency seismic waves, the slope gradient PGA amplification factor increases with the increase of the frequency similarity ratio.