NUMERICAL SIMULATION FOR AMPLIFICATION EFFECT OF TOPOGRAPHY AND GEOMORPHOLOGY TO SEISMIC WAVES

Many numerical analyses are carried out using the software Flac3D to investigate the amplification effect of topography and geomorphology on seismic waves. Research findings indicate that both the peak acceleration of natural seismic wave and harmonic wave can be amplified linearly in the vertical direction and along the surface of the slope when the single-sided slope is low. When the single-sided slope is high and the slope angle is small, the acceleration contour lines of the two waveforms can be parallel to the slope surface approximately. At the same time, the effect of extremum under the top of the single-sided slope is unobvious, and becomes more obvious with the slope angle increasing and there are some rhythmical local minimum strips which are parallel to the slope surface and have the tend to become one strip with the slope angle increasing for natural seismic waves. There are some rhythmical local minimum strips which are parallel to the slope surface for harmonic wave no matter the slope angle is low or high and the effect of extremum under the top of the single-sided slope is not as obvious as natural seismic waves and can disappear with the slope angle increasing. When the slope angle is high, there are some extremal circles in the peak acceleration profiles along the slope surface. The amplification effect on peak acceleration is more intense for thinner ridge of the two-sided slope. The amplification coefficient of crest of two-sided slope tends to be a stable value with the width of the two-sided slope increasing. The amplification effect of two-sided slope on peak acceleration is more intense than the single-sided slope. The amplification effect of multimodal slope on peak acceleration is more intense than that of bimodal slope and the amplification effect of bimodal slope on peak acceleration is more intense than that of unimodal slope. The amplification effect on peak acceleration is more obvious on the upper half of the V-shaped valley than that of U-shaped valley. However, the dynamic response on the middle bottom of U-shaped valley is stronger than that of U-shaped valley. The local irregularities on the surface of a slope can only have effect on the local distribution of peak acceleration near the surface of the slope. The key factors to the distribution of peak acceleration are slope height, slope angle and geometry of the slope top.