Determination of seismic response of reinforced tunnel portal slope using shaking table tests

Abstract

The tunnel portal is a seismically weak part of the tunnel. To improve the seismic performance of the tunnel portal, reliable portal slope reinforcement measures were investigated, and a series of shaking table tests of the tunnel portal and slope which were reinforced by micropiles were conducted. The test equipment, similarity relation, material, test process, and loading conditions were introduced in detail. Two types of earthquake waves (Kobe and Wenchuan waves), whose peak accelerations were modified to 0.125 g, 0.25 g, 0.375 g, 0.5 g, and 0.7 g, were input in the transverse direction. Through the application of the Pearson correlation coefficient, 2-norm deviation, fast Fourier transform, frequency transfer function, Hilbert-Huang transform, and other means, an in-depth analysis of the data was conducted; the results indicated that the micropiles can effectively reduce the effect of the portal slope on the amplification of acceleration, lower the acceleration response of surrounding rock, improve the predominant frequency of surrounding rock, slow down the damage of the tunnel portal slope due to vibration, and decrease the internal force of the lining.