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1.
The dynamic soil-tunnel interaction is studied by the model of a rigid tunnel embedded in layered half-space,which is simplified as a single soil layer on elastic bedrock to the excitation of P- and SV-waves.The indirect boundary element method is used,combined with the Green's function of distributed loads acting on inclined lines.It is shown that the dynamic characteristics of soil-tunnel interaction in layered half-space are different much from that in homogeneous half-space,and that the mechanism of soil-tunnel interaction is also different much from that of soil-foundation-superstructure interaction.For oblique incidence,the tunnel response for in-plane incident SV-waves is completely different from that for incident SH-waves,while the tunnel response for vertically incident SV-wave is very similar to that of vertically incident SH-wave. 相似文献
2.
Weighted residual method for diffraction of plane P-waves in a 2-D elastic half-space III: on an almost circular arbitrary-shaped alluvial valley 
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下载免费PDF全文 Scattering and diffraction of elastic in-plane P- and SV-waves by a surface topography such as an elastic canyon at the surface of a half-space is a classical problem which has been studied by earthquake engineers and strong motion seismologists for over forty years. The case of out-of-plane SH-waves on the same elastic canyon that is semicircular in shape on the half-space surface is the first such problem that was solved by analytic closed-form solutions over forty years ago by Trifunac. The corresponding case of in-plane P- and SV-waves on the same circular canyon is a much more complicated problem because the in-plane P- and SV- scattered waves have different wave speeds and together they must have zero normal and shear stresses at the half-space surface. It is not until recently in 2014 that analytic solution for such problem is found by Lee and Liu. This paper uses their technique of defining these stress-free scattered waves, which Brandow and Lee previously used to solve the problem of the scattering and diffraction of these in-plane waves on an almost-circular surface canyon that is arbitrary in shape, to the study of the scattering and diffraction of these in-plane waves on an almost circular arbitrary-shaped alluvial valley. 相似文献
3.
To identify the key features of the free-field response for inplane motion, a vast parametric study is performed, varying the location of the control point, the nature of the wave pattern and the site properties. Harmonic excitation for a site consisting of a layer on bedrock is investigated. The nature of the wave pattern producing the site response is classified with respect to the apparent velocity of the motion propagating horizontally across the site. When the control point is selected at the outcrop of the bedrock, the amplification of the motion to the free surface of the site depends on the angle of incidence of the incoming wave in the bedrock. The amplification of the vertical motion for incident P-waves hardly depends (with a tendency of being somewhat larger compared to vertical incidence) on the angle of incidence in the bedrock. The amplification of the horizontal motion for incident SV-waves is affected strongly by the angle of incidence, being larger or smaller than for vertical incidence. Interpreting the two components of the motion at the free surface as arising from a combination of incident P- and SV-waves leads to amplifications within the site (for the horizontal and vertical directions) which do not depend, from a practical point of view, on the angle of incidence and on the prescribed motion up to the fundamental frequency in the horizontal and vertical directions, respectively. The variation of the motion for the first Rayleigh-mode with depth in the two directions bears comparison, in general, with that of vertically incident waves up to the corresponding fundamental frequency. The higher Rayleigh-modes lead to a completely different variation with depth. In contrast to Rayleigh-waves the attenuation of the motion in the horizontal direction for inclined body waves depends on the damping of only the bedrock. Rayleigh-waves thus attenuate more strongly than body waves, especially in the higher-frequency range. Generally, higher Rayleigh-modes attenuate less than the first. 相似文献
4.
Alejandro Rodríguez-Castellanos Manuel Carbajal-Romero Norberto Flores-Guzmán J. Efraín Rodríguez-Sánchez Andriy Kryvko 《地震工程与工程振动(英文版)》2017,16(3):571-585
This study quantifies seismic amplifications in near-shore arising from seaquakes. Within the Boundary Element Method, boundary elements are used to irradiate waves and force densities obtained for each element. Huygens′ Principle is implemented since the diffracted waves are constructed at the boundary from which they are radiated, which is equivalent to Somigliana′s theorem. Application of boundary conditions leads to a system of integral equations of the Fredholm type of second kind and zero order. Several numerical configurations are analyzed: The first is used to verify the present formulation with ideal sea floor configurations to estimate seismic amplifications. With the formulation verified, simple slope configurations are studied to estimate spectra of seismic motions. It is found that P-waves can produce seismic amplifications from 1.2 to 3.9 times the amplitude of the incident wave. SV-waves can generate seismic amplifications up to 4.5 times the incident wave. Another relevant finding is that the highest amplifications are at the shore compared to the ones at the sea floor. 相似文献
5.
以Biot饱和多孔介质动力学理论为基础,利用Fourier Bessel级展开法,给出了饱和多孔介质半空间中半球形凹陷地形对入射平面SV波散射问题的解析解.利用这一解析解数值计算地表位移幅值,分析入射角、入射波频率对地表位移幅值的影响,并与现存的单相介质情况下三维半球形凹陷问题解析解进行对比得出如下结论：(1)本文两相介质模型与单相介质模型有很大区别;(2)入射角、入射频率对场地表面位移分量有重要影响;(3)随着入射角、入射频率的增大,地表位移分布变得更复杂,且放大效应比单相介质模拟结果更加显著. 相似文献
6.
The spatial and temporal characteristics exhibited by earthquake ground motions at points below the soil surface have important implications for both deeply embedded structures and for spatially extended constructed facilities. In most cases, the characteristics of the seismic motion are known only at the surface, since it is there where most (but not all) of the historical earthquake records have been obtained. While downhole arrays can provide valuable additional information on motion statistics below the surface, it is both possible and desirable to supplement the available database with predictive computational models. With this goal in mind, this paper presents an analytical model to estimate the statistical properties of seismic motions at any point in the ground on the basis of the statistical properties obtained from records on the surface. The emphasis is on the particular cases of stationary SH-waves propagating in a multi-layered soil, and of stationary P-waves propagating in a half-space. The stochastic deconvolution model considered here is based on a formulation with matrices of spectral density functions. Together with the existing formulation based on cross-correlation matrices proposed earlier by Kausel and Pais (J. Engng Mech. Div., ASCE 113 (2) (1998) 266–277), this stochastic deconvolution technique will be referred to as the Complete Stochastic Deamplification Approach (CSDA). The results obtained show that the reduction in the intensity of shaking with embedment is more pronounced when SH-waves propagate in a stratified soil than when they propagate in a homogeneous half-space. Also, it is found that incident P-waves exhibit greater coherency than incident SH-waves, an indication that it is important to distinguish between such wave types when developing coherence models from array data. 相似文献
7.
Influence of seismic wave type and incident direction on the dynamic response of tall concrete-faced rockfill dams 下载免费PDF全文
下载免费PDF全文 Owing to the stochastic behavior of earthquakes and complex crustal structure, wave type and incident direction are uncertain when seismic waves arrive at a structure. In addition, because of the different types of the structures and terrains, the traveling wave effects have different influences on the dynamic response of the structures. For the tall concrete-faced rockfill dam (CFRD), it is not only built in the complex terrain such as river valley, but also its height has reached 300 m level, which puts forward higher requirements for the seismic safety of the anti-seepage system mainly comprising concrete face slabs, especially the accurate location of the weak area in seism. Considering the limitations of the traditional uniform vibration analysis method, we implemented an efficient dynamic interaction analysis between a tall CFRD and its foundation using a non-uniform wave input method with a viscous-spring artificial boundary and equivalent nodal loads. This method was then applied to investigate the dynamic stress distribution on the concrete face slabs for different seismic wave types and incident directions. The results indicate that dam-foundation interactions behave differently at different wave incident angles, and that the traveling wave effect becomes more evident in valley topography. Seismic wave type and incident direction dramatically influenced stress in the face slab, and the extreme stress values and distribution law will vary under oblique wave incidence. The influence of the incident direction on slab stress was particularly apparent when SH-waves arrived from the left bank. Specifically, the extreme stress values in the face slab increased with an increasing incident angle. Interestingly, the locations of the extreme stress values changed mainly along the axis of the dam, and did not exhibit large changes in height. The seismic safety of CFRDs is therefore lower at higher incident angles from an anti-seepage perspective. Therefore, it is necessary to consider both the seismic wave type and incident direction during seismic capacity evaluations of tall CFRDs. 相似文献
8.
A two-dimensional (2-D) model of a building supported by a rectangular, flexible foundation embedded in the soil is analyzed for excitation by an incident plane SV-wave. The incidence is below the critical angle. The building is assumed to be anisotropic and linear while the soil and the foundation are assumed to be isotropic and can experience nonlinear deformations. In general the work spent for the development of nonlinear strains in the soil can consume a significant part of the input wave energy and thus less energy is available for the excitation of the building. We show that the energy distribution in the building depends on the nature of the incident wave and differs substantially between the cases of incident P- and SV-waves. However, for both excitation by a plane SV-wave pulse and excitation by a P-wave, we show that the nonlinear response in the soil and the foundation does not significantly change the nature of excitation of the base of the building. It is noted that the building response can be approximated by translation and rocking of the base only for excitation by long, strong motion waves. 相似文献
9.
A procedure to calculate the three-dimensional harmonic response of a infinitely long cylindrical shell of circular cross-section embedded in a layered viscoelastic half-space and subjected to harmonic plane waves impinging at an oblique angle with respect to the axis of the shell is validated by extensive comparisons with previous two- and three-dimensional results for the particular case of a shell embedded in a uniform half-space. New numerical results describing the motion and stresses within a shell embedded in a multilayered half-space and subjected to obliquely incident P-, SV- and SH-waves with different horizontal angles of incidence are presented and discussed. 相似文献
10.
J. W. M. DANKBAAR 《Geophysical Prospecting》1983,31(6):873-887
A theoretical study is presented of the effect of source/receiver patterns with fixed phase difference on the radiation/receiving characteristics of the single elements of the pattern in linear elastic media. The radiation characteristic of two vertical vibrators in phase and in counterphase is investigated in detail. By introducing source/receiver patterns the characteristics become dependent on dimension of the pattern, frequency and angle of observation in the horizontal plane. The types of waves generated by source patterns are, independent of phase differences, equal to those generated by single sources. With two vertical vibrators in phase radiation of P-waves can be improved relative to that of SV-waves. With two vibrators in counterphase radiation of SV-waves in vertical directions is enhanced relative to that of P-waves; this may be a valuable method of SV-shear wave generation in exploration seismics. SV-wave amplitudes larger than P-wave amplitudes can be expected at angles larger than 5°–10° with the vertical. 相似文献
11.
Chi Hsin Lin Vincent W. Lee Maria I. Todorovska Mihailo D. Trifunac 《Soil Dynamics and Earthquake Engineering》2010
The zero-stress boundary conditions at the surface of the half-space in the presence of surface and sub-surface cavities for in-plane, incident cylindrical P- and SV-waves have always posed challenging problems. The outgoing cylindrical P- and SV-waves can be represented by Hankel functions of radial distance coupled with the sine and cosine functions of angle. Together, at the half-space surface the P- and SV-wave functions are not orthogonal over the semi-infinite radial distance from 0 to infinity. Thus, to simultaneously satisfy the zero in-plane, normal, and shear stresses, an approximation of the geometry is often made. This paper presents an analytical formulation of the boundary-valued problem, where the Hankel wave functions are expressed in integral form, changing the representation from cylindrical to rectangular coordinates, so that the zero-stress boundary conditions at the half-space surface can be applied in a more straightforward way. 相似文献
12.
在层状半空间精确动力刚度矩阵和斜线荷载动力格林函数的基础上建立间接边界元方法,在频域内求解无破碎带断层场地对入射平面SH波的散射。为方便求解,将总波场分解为自由波场和散射波场,自由波场由直接刚度法求得,断层两侧的散射波场通过在断层面上分别对两侧施加均布斜线荷载产生的动力响应来模拟,虚拟荷载的密度可通过引入断层表面的边界条件确定,最后叠加自由波场和散射波场求得总波场。以有落差断层和无落差断层模型为例进行数值计算,分析断层落差、断层倾角以及断层两侧介质的刚度比对散射效应的影响。研究表明,断层落差与波长相当时,断层对SH波的放大作用最大;地表位移幅值随着断层倾角的增大逐渐增大;若断层无落差且其两侧刚度不同时,一般刚度较小一侧地表位移幅值较大且振荡更为剧烈,波从刚度较小一侧入射时位移幅值放大尤为显著。 相似文献
13.
基于间接边界元法计算沉积河谷对平面P波和SV波的二维散射,着重考察沉积介质波速和材料阻尼的随机性对河谷地震动放大效应。利用蒙特卡罗方法随机模拟产生了波速样本和阻尼样本各30组,给出了不同入射角度和频率P波和SV波入射下河谷随机响应的单频和频谱结果。算例分析结果表明:(1)地表位移响应幅值的变异系数极值均显著大于波速比变异系数,且波速比的随机性对地表位移的影响在体系共振频率处最为明显,地表位移的最大标准差可达7.168;低频情况下,沉积中部地震反应变异性更显著,高频情况下则在沉积河谷边缘变异性最大;(2)入射波角度对地表位移响应变异系数极值的影响不大,但对变异系数空间变化的影响显著;(3)阻尼的随机性对地表位移的影响在低频情况下较小,在高频情况下则较明显,尤其是在沉积河谷的体系自振频率处,其影响最为显著。 相似文献
14.
Weighted residual method for diffraction of plane P-waves in a 2-D elastic half-space Ⅲ: on an almost circular arbitrary-shaped alluvial valley 下载免费PDF全文
下载免费PDF全文 Scattering and diffraction of elastic in-plane P-and SV-waves by a surface topography such as an elastic canyon at the surface of a half-space is a classical problem which has been studied by earthquake engineers and strong motion seismologists for over forty years. The case of out-ofplane SH-waves on the same elastic canyon that is semicircular in shape on the half-space surface is the first such problem that was solved by analytic closed-form solutions over forty years ago by Trifunac. The corresponding case of in-plane P-and SV-waves on the same circular canyon is a much more complicated problem because the in-plane P-and SV-scattered waves have different wave speeds and together they must have zero normal and shear stresses at the half-space surface. It is not until recently in 2014 that analytic solution for such problem is found by Lee and Liu. This paper uses their technique of defining these stress-free scattered waves, which Brandow and Lee previously used to solve the problem of the scattering and diffraction of these in-plane waves on an almost-circular surface canyon that is arbitrary in shape, to the study of the scattering and diffraction of these in-plane waves on an almost circular arbitrary-shaped alluvial valley. 相似文献
15.
James Gaiser 《Geophysical Prospecting》2019,67(9):2414-2431
Utilizing shear-wave (S-wave) data acquired with compressional waves (P-waves) is becoming more common as joint imaging and inversion techniques improve. Interest in S-waves radiated from vertical sources and buried explosives exploits conversion to P-waves as primary reflections (SP-waves) for reducing acquisition costs and for application to legacy data. However, recent investigations overstate the extent of SP-wave illumination and show isotropic processing results with narrow bandwidth frequency and wavenumber data. I demonstrate that illumination with SP-waves is limited in general to near vertical polar angles up to around 30° or 35° for VP/VS of 2 or 3, respectively. At greater angles, S-waves are typically in the P-wave evanescent range and cannot excite SP-wave reflections. Contrary to recent claims, these sources for P-wave do not radiate SH-waves polarized in horizontal planes in all azimuths. I show these properties for isotropic media with radiation expressions for amplitude derived in vector slowness coordinates. Also, I extend these expressions to transversely isotropic media with a vertical symmetry axis to show agreement with synthetic seismic data that only quasi SV-waves are radiated and become more narrowly focused towards 45°. Furthermore, in orthorhombic media, synthetic data show that fast S1- and slow S2-waves polarized parallel and perpendicular to fractures may appear as SV- and SH-waves. For the partially saturated fracture model studied here, S1-wave radiation has broader azimuthal illumination than slow S2-waves, which are more narrowly focused in azimuth. These produce SP-wave splitting signatures on vertical component reflection data that are nearly identical to PS-wave signatures on radial horizontal component data. Separating these fast and slow SP-waves is an additional processing challenge. 相似文献
16.
《地震科学（英文版）》2019,(Z1)
A two and a half dimensional(2.5 D) multidomain indirect boundary element method(IBEM) is developed to study the wave scattering of obliquely incident P-, SVand SH-waves by a hill-valley staggered topography in a multi-layered half-space. The IBEM algorithm includes using2.5 D full-space and half-space Green's functions to construct scattered fields in decomposed closed and opened half-space regions, respectively, and using the dynamic stiffness method to solve the free fields. All regions are finally integrated by introducing the compatibility conditions to obtain the total wave fields. The proposed 2.5 D IBEM has the flexibility in dealing with complex boundaries by directly applying the fictitious loads on the regions' boundaries, with a less storage requirement compared to the full 3 D models. Besides, by combining the specific advantages of the two kinds of Green's functions, the method is well suitable for handling coupled topographies with high accuracy. The method is validated by comparison with published results for a single valley as well as a single hill topography. The effects of height-to-width ratio of hill and layering on dynamic responses are further parametrically investigated by numerical implementations in frequency domain. Results show that the interaction between valley and hills can lead to a more significant amplification within the valley region, and dynamic responses are deeply influenced by the height-towidth of hill, simultaneously depending on incident angle and frequency. Besides, the site effects become more complex when the stratification feature is taken into account. 相似文献
17.
A well-defined boundary-valued problem of wave scattering and diffraction in elastic half-space should have closed-form analytic solutions. This two-dimensional (2-D) scattering around a semi-circular canyon in elastic half-space subjected to seismic plane and cylindrical waves has long been a challenging boundary-value problem. In all cases, the diffracted waves will consist of both longitudinal (P-) and shear (S-) rotational waves. Together at the half-space surface, these in-plane longitudinal P- and shear SV-waves are not orthogonal over the infinite half-space flat-plane boundary. Thus, to simultaneously satisfy both the zero normal and shear stresses at the flat-plane boundary, some approximation of the geometry and/or wave functions often has to be made, or in some cases, relaxed (disregarded). This paper re-examines this two-dimensional (2-D) boundary-value problem from an applied mathematics points of view and redefines the proper form of the orthogonal cylindrical-wave functions for both the longitudinal P- and shear SV-waves so that they can together simultaneously satisfy the zero-stress boundary conditions at the half-space surface. With the zero-stress boundary conditions satisfied at the half-space surface, the most difficult part of the problem will be solved, and the remaining boundary conditions at the finite-canyon surface are then comparatively less complicated to solve. This is now a closed-form analytic solution of the 2-D boundary-valued problem satisfying the half-space zero-stress boundary conditions exactly. 相似文献
18.
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
19.
Hasan Faik Kara 《地震工程与工程振动(英文版)》2020,19(2):289-305
Dynamic response of an alluvial valley consisting of three different types of soil was studied. In the two-dimensional model, the alluvial valley was assumed to have half-cylindrical shape. The alluvial valley contained three different types of soil with different shapes. The valley was surrounded by a half-space. All of the soil types and the half-space were assumed to be isotropic, homogeneous and linear elastic. The half-space was excited by simple harmonic SH-waves radiated from a strike-slip fault. The fault was assumed to have circular-arc shape in the mathematical model. The governing equations were solved by using wave function expansion method where boundary conditions were relatively simple. In the regions where boundary conditions were more complex, finite difference method was employed. Consequently, the wave propagation problem was solved semi-analytically. The obtained numerical results showed that surface displacement amplitudes are significantly affected by the material properties of the different soil types of the alluvial valley. It was also observed that the shapes of the soil types in the alluvial valley played a considerable role in surface displacements. 相似文献