Abstract:

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.

Key words: dynamic centrifugal model test, tunnel, medium-stiff soil, traditional spectral ratio method, site amplification effect