含隧道场地地震动放大效应的深度变化规律研究

以剑桥大学工程系完成的含圆形隧道的动力离心模型试验结果为基础数据，在80g重力加速度条件下，从模型基底处由弱至强输入4 种地震波 EQ1～EQ4，利用在叠环式模型箱内不同位置布设加速度传感器，获取了不同层位深度处隧道列的加速度时程记录，运用考虑相消干涉的传统谱比法，分析研究了地震作用下含隧道的场地放大效应随深度变化规律。研究结果表明：在EQ1～EQ4下各振型的地震动放大系数随深度变化曲线从基底到地表大部分呈现一个先减小后增大的现象；并统计到高阶振型地震动放大系数数值大于一阶振型的概率为 18.3%，振型越高，概率越大；近地表处地震动放大系数的最大值主要分布在 4.20～8.63 Hz的中部频段上，而不是出现在低频段上。

Study on variation law of ground motion amplification effects along depth in tunnel site

Based on the results of dynamic centrifugal model test with circular tunnel completed by the Engineering Department of Cambridge University, four different kinds of seismic waves EQ1-EQ4 from weak to strong were input at the base of the model under the condition of 80g gravity acceleration, and acceleration sensors were arranged at different positions in the laminated model box to measure the acceleration time history at different depths along the tunnel location. Using the traditional spectral ratio method considering destructive interference, the variation law of site amplification effect with depth under earthquake was analyzed and studied. The results show that under EQ1-EQ4, the ground motion amplification factor of each vibration mode decreases first and then increases from the base to the surface. According to the statistics, the probability that the value of ground motion amplification factor of high-order mode is larger than the first-order mode is 18.3%. The higher the mode, the greater the probability. The maximum value of ground motion amplification factor near the surface is mainly distributed in the middle frequency band of 4.20 – 8.63 Hz, rather than in the low frequency band.