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1.
The effect of topography and subsurface inhomogeneity on surface motion is investigated in the case of Rayleigh waves. In the previous paper, the same effect was investigated in the case of SV waves. Several types of topography, such as cliffs both with and without a soft layer at the foot of the slope, are considered. Computations are made using a new hybrid method combining a particle model with a finite element method. In cases of harmonic Rayleigh waves, surface motions with amplitudes as large as 1.5 to 5 times the horizontal surface displacement of the incident Rayleigh waves are produced near the slope and the sloping interface. When a Rayleigh wave propagating through a hard single-layered ground encounters a sloping interface where hard ground and soft ground make contact with each other, Rayleigh waves having two different, phase velocities are produced and they correspond to the fundamental mode, and the first mode determined by Haskell's method. In addition, the transient response when Rayleigh waves propagate through the cliff is also simulated. Assuming the vertical component of the Tokachi-oki Earthquake (1968) measured on the surface to be a Rayleigh wave, the incident Rayleigh wave can be obtained by a Fourier synthesis of eigenfunctions of Rayleigh waves. 相似文献
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结合单相介质动力格林函数和流体域格林函数,将间接边界元方法拓展到含流体层河谷对地震波散射的求解,并结合具体算例进行大量参数分析。研究结果表明,含流体层河谷地形对平面P波、SV波入射时的地震响应受控于入射波频率、入射波角度及流体深度等多种因素。总体来看:① 在低频域内,含流体河谷底部及附近地表的频谱特性与不含流体的河谷反应基本一致;② P波入射时在水层体系共振频率处,河谷底部位移缩小效应显著,而此频率处流体表面位移达到最大;③ 流体层具有吸收地震波能量的作用,流体深度越大,河谷表面及附近地表的地震动位移越小。研究成果可在一定程度上为河谷地形附近地震动效应的评估及防震减灾工作提供理论依据。 相似文献
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基于黏弹性人工边界的显式动力有限元方法,研究了突出平台状山谷地形场地的地形效应,分析了山谷地形对地表地震动的影响.结果表明:(1)沿着地震动输入方向地表反应较其他方向上的反应强烈;(2)与单一凸起山体地形对地表地震动的放大效应相比,相邻地形的存在对地表地震动位移傅里叶谱谱比曲线的形状影响不大,但是对PGD有着较大的影响... 相似文献
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刘晶波 《地震学报(英文版)》1996,9(2):309-315
Theeffectoflocalirregulartopographyonseismic ground motionJIG-hoLIU(刘晶波)(DepartmentofCivilEngineering,TsinghuaUniversityBeiji... 相似文献
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采用波函数展开法,并借助辅助函数思想,给出了平面SV波入射下半圆凸起地形地表运动的一个解析解,并对解答的收敛性和截断计算精度进行了检验;最后通过若干算例分析了入射频率和入射角度以及凸起地形宽度对地表运动的影响. 数值结果表明,凸起地形对入射SV波具有显著的放大作用, 该放大作用可达自由场的4倍以上. 当入射频率较低时, 位移峰值多位于半空间地表; 而当入射频率较高时,位移峰值多位于凸起地形表面. 相似文献
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Introduction Scattering of incident waves by local topographies is one of the most attractive topics in the field of engineering seismology. They can be resolved by either a numerical method or an analyti-cal method. The numerical methods include finite difference method, finite element method, boundary element method, etc. The analytical method is the wave function expansion method. Al-though numerical methods can be used for arbitrary-shaped topographies, the analytical solutions are still … 相似文献
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P. Dangla 《地震工程与结构动力学》1988,16(8):1115-1128
A plane strain model for dynamic soil-structure interaction problems under harmonic state is presented. The boundary element method is used to study the response of a homogeneous isotropic linear elastic soil. The far field displacement at the free surface is approximated by an outgoing Rayleigh wave. The finite element method is used to describe the response of the building, of the foundation and possibly of a finite part of the inhomogeneous non-linear soil. Two coupling procedures are described. The model is applied to a problem previously studied in the antiplane case. Incident P, SV and Rayleigh waves are considered. The results show an amplification and an attenuation of the structure motion with frequency when incident Rayleigh waves and P, SV body waves are respectively considered. 相似文献
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An explicit finite difference method is performed to evaluate the significance of topography effects on the seismic response of viscoelastic sites. The real accelerograms and bell-shape impulse wavelets, slope angle of cliff and angle of incidence on the spectrum property of the incoming waves are all discussed in detail. The conclusions show that the presence of topographic factors and the direction of the incident waves not only significantly affect the peak ground acceleration of a site, but also affect the spectrum properties of the incoming waves, and the effect on the direction of the incident waves is especially remarkable. The study also finds that it is reasonable to analyse spectrum properties with the input of impulse wavelets in the finite element simulation of wave motion. 相似文献
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局部地形对出平面运动谱特性的影响分析 总被引:3,自引:0,他引:3
本文利用显式有限元有限差分方法进行了脉冲和实际地震动输入下的粘弹性场地地形影响的分析计算,研究了坡地地形在高宽比不同、体波入射角度不同时出平面运动谱特性的差异。结果显示:地形的特征尺寸和入射角度不仅对地震动的峰值有影响,而且对地震动的谱特性有较大的影响,其中入射角度的影响尤为显著。另外,研究还表明,基于脉冲输入研究粘弹性地形谱特性的影响仍不失为一种有效的方法。 相似文献
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Seismic stability of slopes has been traditionally analyzed with vertically propagated earthquake waves. However, for rock slopes, the earthquake waves might approach the outcrop still with a evidently oblique direction. To investigate the impact of obliquely incident earthquake excitations, the input method for SV and P waves with arbitrary incident angles is conducted, respectively, by adopting the equivalent nodal force method together with a viscous-spring boundary. Then, the input method is introduced within the framework of ABAQUS software and verified by a numerical example. Both SV and P waves input are considered herein for a 2D jointed rock slope. For the jointed rock mass, the jointed material model in ABAQUS software is employed to simulate its behavior as a continuum. Results of the study show that the earthquake incident angles have significance on the seismic stability of jointed rock slopes. The larger the incident angle, the greater the risk of slope instability. Furthermore, the stability of the jointed rock slopes also is affected by wave types of earthquakes heavily. P waves induce weaker responses and SV waves are shown to be more critical. 相似文献
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SV波入射情况下V型河谷地形对地震动的影响分析 总被引:2,自引:0,他引:2
基于局部人工边界的显式有限元方法,给出了二维V型河谷地形在SV波垂直人射下地面运动数值解,并分析其地震动分布规律以及两侧不同的边坡角度对于地震动分布规律的影响.数值结果表明:谷底的角点、两岸靠近河谷的点、两侧谷坡靠近谷底的点以及靠近两岸的点,对地表位移有放大作用,而对其邻近区域地表位移有抑制作用.这是由于角点处存在面的... 相似文献
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本文采用隐式动力有限单元法研究了不同的边坡角度和边坡高度对地形放大效应的影响,并以位移峰值放大系数为衡量地震动放大效应的标准,计算了不同边坡角度和边坡高度条件下的地震响应,在此基础上对模型关键监测点的输出波形以及位移峰值放大系数的变化趋势进行了分析,获得了不同监测点处的地震动时程曲线,揭示了坡角和坡高对单体边坡地震动放大效应的定量作用规律。数值结果表明,相同高度处坡面监测点的水平向位移峰值放大系数大于坡内监测点的,地形放大效应在水平方向具有趋表效应。由于坡面存在入射波和反射波的叠加,因此竖直向位移峰值放大系数的最大值出现在坡体内部。 相似文献
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In this paper we have simulated the propagation of seismic waves in viscoelastic medium and calculated the effect of irregular
surface topography by using finite element method. Several types of elastic and viscoelastic medium models, such as block
structure, vidges and/or valley with and without a soft layer underneath have been studied. The distribution of maximum amplitude
of displacement and acceleration on surface has been calculated in the case of vertically incident SH and P waves from the
basement. The possible application in earthquake engineering is also discussed.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 442–449, 1991. 相似文献
15.
A series solution for surface motion amplification due to underground twin tunnels: incident SV waves 总被引:7,自引:0,他引:7
A series solution of displacement response of the ground surface in the presence of underground twin tunnels subjectcd to excitation of incident plane SV waves is derived by using Fourier-Bessel series expansion method. The numerical parametric study shows that underground twin tunnels significantly amplify the nearby surface ground motion. It is suggested that the effect of subways on ground motion should be considered when the subways are planned and designed. 相似文献
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Three-dimensional scattering of seismic waves by a cylindrical alluvial valley embedded in a layered half-space is investigated by using the combination of the boundary integral representation and the finite element method. The surface displacements due to incident plane harmonic body waves (P, SV and SH) propagating at an arbitrary angle to the axis of the cylindrical valley are evaluated numerically for two semi-elliptical alluvial valleys. The presence of the layer is found to have a strong effect on the amplification of the surface displacements in some cases. The three-dimensional motion seems to be quite critical and may cause large amplification. The surface ground motion becomes significant when compared with corresponding free-field motion as the wavelengths become comparable to the characteristic length of the valley. The maximum amplification always occurs atop the valley. Numerical results show that the amplitude and the amplification pattern of the surface displacement strongly depend upon the frequency, the angle and the type of the incident waves. 相似文献
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基于饱和两相介质弹性波动方程分析SV波在饱和土体自由表面的反射问题,引入波动方程的势函数解答,求解出二维问题中SV波入射情况下饱和土体自由场的位移、速度、加速度和应力响应。在饱和土体自由场响应解析解基础上,建立SV波入射下饱和土体自由场静、动力有限元模型。建模中考虑了如下几方面因素:(1)在不同分析步,对土体单元赋予不同材料本构。通过*model change命令进行单元生死设定,从而实现在初始应力场平衡的静力状态下采用DuncanChang本构模型,而地震波动输入时采用Davidenkov动力本构模型;(2)采用多孔介质黏弹性人工边界条件,在人工边界上分别施加固相和液相介质的弹簧和阻尼来模拟饱和土体中能量的传播;(3)将地震波转化为作用在人工边界上的等效地震荷载,施加到人工边界节点上;(4)土体单元采用4结点平面应变孔压单元(CPE4P)。有限元计算与解析解比较结果表明:SV波在垂直入射和掠入射时,竖向位移响应为零;在45°左右入射时,水平位移响应最大;60°左右入射时,竖向位移响应最大。这些结论与解析解吻合较好,本文模型为建立土-结构动力相互作用模型打下良好的基础。 相似文献
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Dynamic interaction of twin vertically overlapping lined tunnels in an elastic half space subjected to incident plane waves
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The scattering of plane harmonic P and SV waves by a pair of vertically overlapping lined tunnels buried in an elastic half space is solved using a semi-analytic indirect boundary integration equation method. Then the effect of the distance between the two tunnels, the stiffness and density of the lining material, and the incident frequency on the seismic response of the tunnels is investigated. Numerical results demonstrate that the dynamic interaction between the twin tunnels cannot be ignored and the lower tunnel has a significant shielding effect on the upper tunnel for high-frequency incident waves, resulting in great decrease of the dynamic hoop stress in the upper tunnel; for the low-frequency incident waves, in contrast, the lower tunnel can lead to amplification effect on the upper tunnel. It also reveals that the frequency-spectrum characteristics of dynamic stress of the lower tunnel are significantly different from those of the upper tunnel. In addition, for incident P waves in low-frequency region, the soft lining tunnels have significant amplification effect on the surface displacement amplitude, which is slightly larger than that of the corresponding single tunnel. 相似文献
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