Abstract
A sedimentary valley has a visible amplification effect on a seismic response, and the current 2D topographies cannot truthfully reflect the twists and turns of a large-scale river valley. Taking a sinusoidal curved valley site as a model, the dynamic finite element analysis method and the introduction of a viscoelastic artificial boundary were developed to study the 3D seismic response of the dimensional topographies in the homogeneous curved valley to vertical incident P, SV, and SH waves. The results showed that the bending sedimentary valley site earthquake presented significant features simultaneously, depending on the number of valley bends, the frequency of the excitations, the shear wave velocity of sedimentary soil, and the depth of the river valley. The surface displacement amplitudes of three-dimensional meandering sedimentary valleys are significantly different from those of sedimentary basins. The amplification area of the meandering valley is related to the angle between the valley axis and wave vibration direction, and the amplification effect is significant when the angle is small. The movement in the main direction showed a center focus, and the secondary y-direction displacement showed both a central focus and an edge effect. When the frequency of the incident wave was close to the natural vibration frequency in a specific direction, the movement in this direction significantly increased because of the resonance effect. The displacement amplitude of the surface was proportional to the depth of the river valley, and the surface displacement was presented in different forms based on the frequency of the excitations. The results provided some guidance for the earthquake resistance of the curved valley site.
Highlights
Introduction ere are many rivers inChina, especially in the western region
Because there are more than ten million three-dimensional model units, calculations are relatively challenging to conduct. erefore, this study introduced a harmonic response analysis to evaluate the frequency domain solution of a three-dimensional model. e equivalent load in the time domain was transformed into an equivalent load in the frequency domain using the fast Fourier transform, and the surface displacement of a meandering sedimentary valley site with an incident SV wave was analyzed
It was verified that this method could effectively solve the frequency domain analysis of ground motion in a sedimentary valley. e study showed that, for vertical incidence of P wave, SV wave, and SH wave, seismic response of the threedimensional sedimentary valley meander is mainly determined by the incidence frequency (f ), the depth of deposition (H), the sedimentary soil shear wave velocity, the number of meanders (NR), and so on
Summary
Introduction ere are many rivers inChina, especially in the western region. Many important infrastructure projects such as dams and bridges have been built, under construction, and proposed in the valley site. China is a multiearthquake country and the western region is the main strong earthquake area in China; many of these large-scale projects are threatened by the potential earthquake. E phenomenon of terrain effect has been confirmed by a large number of measured seismic records and observed earthquake damage [1,2,3,4,5,6]. Terrain effect is always an important wave problem in seismology, earthquake engineering, and civil engineering. It can be seen that the valley terrain amplification effect has a direct impact on the rationality of the earthquake input in the seismic calculation of large-scale infrastructure projects in China, which will seriously affect the reliability of the seismic design of such projects
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