共查询到19条相似文献，搜索用时 156 毫秒
1.
《地震工程与工程振动》2016,(2)
采用波函数展开法给出了具有圆柱型正交各向异性半圆形沉积谷地形对SH波散射的解答,研究了入射波特性和沉积谷的各向异性对地面运动的影响。稳态SH波入射时,在圆柱型正交各向异性沉积谷中波函数的径向函数满足非整数阶的Bessel方程。数值结果表明:沉积谷地表位移的幅值大小与入射波的频率、入射方向、沉积谷介质的径向与环向剪切模量比及半空间与沉积谷剪切波速比和密度比密切相关,当沉积谷介质比半空间介质软时,沉积谷地表位移幅值明显增大,与各向同性介质的沉积谷地相比,沉积谷介质的各向异性对地面运动的影响非常显著。 相似文献
2.
采用波函数展开法及边界离散的方法给出了任意断面形状的地下夹塞对平面SH波散射的半解析解; 利用蒙特卡罗方法随机模拟产生了30组夹塞断面样本, 通过对该样本在平面SH波入射下地表位移幅值的统计分析, 研究了夹塞断面形状随机性对平面SH波散射的影响. 结果表明, 夹塞断面形状随机性对平面SH波的散射具有重要影响. 以圆形夹塞为例, 当断面半径的变异系数为0.1时, 地表位移响应幅值变异系数可达0.71. 随着入射频率的升高, 变异系数逐渐增大; 随着夹塞刚度的降低, 变异系数逐渐增大; 随着夹塞埋深的增加, 变异系数逐渐减小. 相似文献
3.
采用复函数、多极坐标法研究了含有可移动圆柱形刚性夹杂的弹性半空间对SH波的散射问题。构造一个能自动满足含可移动刚性圆柱的弹性半空间自由表面上应力为零的边界条件的散射波,应用可移动圆柱形刚性夹杂的运动条件来确定该散射波。最终则可将求解问题归结为求解一个无穷代数方程组,采用截断有限项的方法对其进行求解。给出了地表位移幅值的数值结果,并讨论了各种参数对它的影响。 相似文献
4.
SH波在浅埋多个圆孔处的散射与地震动 总被引：1，自引：0，他引：1
研究了以任意方向入射的平面SH波在浅埋多个圆孔处的散射与地震动问题。利用SH散射的对称性和多极坐标方法构造了问题的位移解。当入射波的波长与圆孔的半径相比较小时,地震动将受到较大的影响。影响地震动有三个主要参数:(1)SH波的入射角α0;(2)入射波波数η,即圆形孔洞的半径与入射波半波长之比;(3)诸圆孔的埋置情况,诸孔的埋深hi/ai、孔心距Di/ai,即圆形孔洞至表面距离与圆半径之比和圆形孔洞中心的距离与半径之比。当η较大时,地震动幅值变化激烈,位移幅值可出现跳动和放大的现象。当诸圆孔的最小埋深量hi/ai和孔心距Di/ai超过10-12时,位移幅值恢复至半空间单一圆孔散射的情况,表明圆形孔洞的影响可被忽略。 相似文献
5.
弹性层状半空间中无限长洞室对斜入射 平面SH波的三维散射(Ⅱ) 数值结果与分析 总被引：1，自引：1，他引：0
以基岩上单一土层场地为例, 计算分析了在斜入射平面SH波作用下弹性层状半空间中无限长洞室附近的地表位移. 研究表明, 层状半空间中地下洞室对波的散射与均匀半空间情况存在显著差别. 层状场地由于考虑了场地自身的动力特性, 使得洞室附近地表位移幅值的空间变化更为复杂, 基岩与土层刚度比、 土层厚度对散射效应均有着重要影响. 随着基岩与土层刚度比的增大, 地表位移幅值整体上逐渐增大; 随着土层厚度的增大, 土层对地表位移幅值的影响逐渐减小. 在频域解答的基础上, 给出了层状半空间中洞室对斜入射SH波散射的时域解答, 并以Ricker波为例进行了数值计算. 相似文献
6.
以基岩上单-土层场地为例,计算分析了在斜入射平面SH波作用下弹性层状半空间中无限长洞室附近的地表位移.研究表明,层状半空间中地下洞室对波的散射与均匀半空间情况存在显著差别.层状场地由于考虑了场地自身的动力特性,使得洞室附近地表位移幅值的空间变化更为复杂,基岩与土层刚度比、土层厚度对散射效应均有着重要影响.随着基岩与土层刚度比的增大,地表位移幅值整体上逐渐增大;随着土层厚度的增大,土层对地表位移幅值的影响逐渐减小.在频域解答的基础上,给出了层状半空间中洞室对斜入射SH波散射的时域解答,并以Ricker波为例进行了数值计算. 相似文献
7.
采用波函数展开法及边界离散的方法给出任意断面形状的地下透镜体对平面SH波散射的半解析解,利用蒙特卡罗方法随机模拟产生30组透镜体断面样本,通过对30组具有同一统计特征的任意断面地下透镜体在平面SH波入射下地表动力响应极值的统计分析并与相应椭圆透镜体解答比较,研究透镜体断面形状随机性对平面SH波散射的影响。研究表明,透镜体断面形状随机性对地表动力响应极值具有重要影响。以长短轴比为4的椭圆形透镜体为例,当断面矢径的变异系数为0.1时,样本地表位移响应极值的最大值远大于对应椭圆透镜体解的极值,平均可达47.46%。且增加幅度随着透镜体介质与半空间介质波速差距增大而增大。透镜体埋深越小,增加幅度越大。 相似文献
8.
SH波冲击下浅埋任意形孔洞的动力分析 总被引：5，自引：0，他引：5
求解了稳态SH波垂直弹性半空间水平表面入射时,浅埋任意形孔洞的动力响应。采用复变函数和多极坐标方法构造了一个能够自动满足水平表面上应力自由边界条件的散射波函数。应用这一波函数,将半空间中的问题转化为求解一个全空间中任意形孔洞的散射问题,最终将问题归结为对一组无穷代数方程组的求解。作为对抗爆问题的研究,给出了浅埋椭圆孔和方孔附近的动应力集中系数的数值结果,并对算例进行了讨论。 相似文献
9.
半无限空间中圆形孔洞周围SH波的散射 总被引：14，自引：5，他引：14
建立了求解在含有圆形孔洞的弹性半空间中SH波散射与圆形孔洞附近动应力集中问题的解析方法。利用SH波散射的对称性和多极坐标的方法，构造了一个可以预先满足半空间自由表面上应力自由边界条件的圆形孔洞对SH波散射的波函数。利用这一波函数，则可将该问题转化成对一个圆形孔洞散射的求解问题。该问题的解答最终又可归结为对一组无究代数方程组的求解问题，并可利用截断有限项的方法对其进行计算，最后给出了有关圆形也洞附近动应力集中问题的算例和数值结果，并讨论了波数与圆孔至自由边界距离变化对动应力集中的影响。 相似文献
10.
半无限空间界面附近SH波对圆形衬砌的散射 总被引：6，自引：2，他引：6
建立了求解半无限空间中SH波对浅埋圆形衬砌结构的散射与动应力集中问题的解析方法。利用SH波散射的对称性和多极坐标的方法，在复平面上构造出了一个可以预先满足半空间自由表面上应力自由的边界条件的浅埋圆形衬砌对稳态SH波散射的波函数，并构造出衬砌内的散射波函数。然后根据衬砌周围的边界条件，将该问题转化为对一组无穷代数方程组的求解。最后给出了具体算例，并讨论了其数值结果。 相似文献
11.
平面P波在饱和半空间中洞室周围的散射(II):数值结果 总被引：1，自引：0，他引：1
本文通过数值计算研究了入射平面P波在饱和半空间中洞室周围散射问题,分析了入射波频率和角度、边界渗透条件、孔隙率、泊松比等参数对散射的影响。研究表明,平面P波入射情况下,饱和半空间和单相(干土)半空间中洞室附近地表位移幅值的差别很大,干土情况的水平位移幅值相对较大,饱和情况的竖向地表位移幅值相对较大;由于波在洞室附近的干涉,饱和情况与干土情况的地表位移出现相位漂移。随着孔隙率的增大,洞室附近水平地表位移幅值逐渐减小,竖向地表位移幅值则逐渐增大;当孔隙率较低时,边界渗透条件对地表位移幅值的影响很小,而当孔隙率较大时,边界渗透条件的影响则不可忽视,不透水情况下,水平和竖向地表位移幅值的峰值均相对较大;随着入射频率的增加,孔隙率的影响逐渐增大,而且不透水情况下孔隙率的影响相对较大。随着泊松比的增大,洞室附近水平地表位移幅值逐渐降低,竖向地表位移幅值则逐渐增大;泊松比较小时,边界渗透条件对位移幅值的影响较大,泊松比较大时,边界渗透条件对位移幅值的影响则较小;随着入射频率的增加,泊松比的影响逐渐增大。当孔隙率较小时,半空间地表和洞室表面孔隙水压幅值较小,但空间变化比较剧烈,随着孔隙率的增大,孔隙水压逐渐增大但空间变化逐渐平缓;随着入射频率的增加,孔隙水压幅值逐渐增大,且孔隙水压的空间变化逐渐变得复杂。 相似文献
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Diffraction of obliquely incident waves by a cylindrical cavity embedded in a layered viscoelastic half-space 总被引：1，自引：0，他引：1
The three-dimensional harmonic response in the vicinity of an infinitely long, cylindrical cavity of circular cross-section buried in a layered, viscoelastic half-space is obtained when the half-space is subjected to homogeneous plane waves and surface waves impinging at an oblique angle with respect to the axis of the cavity. The solution is obtained by an indirect boundary integral method based on the use of moving Green's functions for the viscoelastic half-space. Numerical results describing the motion on the ground surface and the motion and stresses on the wall of the cavity are presented for obliquely incident P-, SV-, SH- and Rayleigh waves with different horizontal angles of incidence. 相似文献
13.
Scattering of elastic waves by three-dimensional canyons embedded within an elastic half-space is investigated by using a wave function expansion technique. The geometry of the canyon is assumed to be non-axisymmetric. The canyon is subjected to incident plane Rayleigh waves and oblique incident SH, SV and P waves. The unknown scattered wavefield is expressed in terms of spherical wave functions which satisfy the equations of motion and radiation conditions at infinity, but they do not satisfy stress-free boundary conditions at the half-space surface. The boundary conditions are imposed locally in the least-squares sense at several points on the surface of the canyon and the half-space. Through a comparative study the validity and limitations of two-dimensional approximations (antiplane strain and plane strain models) have been examined. It is shown that scattering of waves by three-dimensional canyons may cause substantial change in the surface displacement patterns in comparison to the two-dimensional models. These results emphasize the need for three-dimensional modelling of realistic problems of interest in strong ground motion seismology and earthquake engineering. 相似文献
14.
针对三维沉积盆地对球面波的散射问题,发展一种快速宽频间接边界元方法(IBEM)。利用ANSYS建立求解模型,基于Intel-Fortran编译器编译相应的计算程序,对基岩半空间三维半椭球形盆地对球面波的散射进行了数值分析,着重探讨入射波频率、波源埋深、波源与不规则地形(沉积盆地)距离等参数对地震动特性的影响规律,计算方法适用于求解任意复杂形状的局部场地,实现对沉积盆地三维地震响应的频域精细求解。研究结果表明:随着入射波频率增大,沉积盆地相对半空间的放大效应越显著,且干涉效应越强烈;高频波入射时,由于盆地底部透射的体波和盆地内部由体波转换为的面波以及从盆地边缘处透射的体波相互叠加,次方向位移出现一定的边缘效应。位移频谱分析表明,沉积盆地在较低频率时,地表不同点位的主方向位移幅值基本相同;在较高频率域内,地表不同点位的位移频谱特性差别很大;球面波入射与平面波入射相比之下,位移幅值均有所降低。整体来看,随着膨胀波源与盆地水平距离增大,地表主方向最大位移幅值降低,地表次方向位移聚焦区域增加且分布更分散。 相似文献
15.
Scattering of incident plane harmonic pseudo P‐, SH‐, and SV‐waves by a two‐dimensional basin of arbitrary shape is investigated by using an indirect boundary integral equation approach. The basin and surrounding half‐space are assumed to be generally anisotropic, homogeneous, linearly elastic solids. No material symmetries are assumed. The unknown scattered waves are expressed as linear combinations of full‐space time‐harmonic two‐dimensional Green functions. Using the Radon transform, the Green functions are obtained in the form of finite integrals over a unit circle. An algorithm for the accurate and efficient numerical evaluation of the Green functions is discussed. A detailed convergence and parametric analysis of the problem is presented. Excellent agreement is obtained with isotropic results available in the literature. Steady‐state surface ground motion is presented for semi‐circular basins with generally anisotropic material properties. The results show that surface motion strongly depends upon the material properties of the basin as well as the angle of incidence and frequency of the incident wave. Significant mode conversion can be observed for general triclinic materials which are not present in isotropic models. Comparison with an isotropic basin response demonstrates that anisotropy is very important for assessing the nature of surface motion atop basins. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
16.
17.
Scattering of SH-wave by multiple circular cavities in half space 总被引：17，自引：1，他引：17
In this paper, an analytic method is developed to address steady SH-wave scattering and perform dynamic analysis of multiple
circular cavities in half space. The scattered wave function used for scattering of SH-waves by multiple circular cavities,
which automatically satisfies the stress-free condition at the horizontal surface, is constructed by applying the symmetry
of the SH-wave scattering and the method of multi-polar coordinates system. Applying this scattered wave function and method
of moving coordinates, the original problem can be transformed to the problem of SH-wave scattering by multiple circular cavities
in the full space. Finally, the solution of the problem can be reduced to a series of algebraic equations and solved numerically
by truncating the infinite algebraic equations to the finite ones. Numerical examples are provided for case with two cavities
to show the effect of wave number, and the distances between the centers of the cavities and from the centers to the ground
surface on the dynamic stress concentration around the cavity impacted by incident steady SH-wave. 相似文献
18.
Marijan Dravinski 《地震工程与结构动力学》2003,32(5):653-670
Scattering of plane harmonic waves by a three‐dimensional basin of arbitrary shape embedded within elastic half‐space is investigated by using an indirect boundary integral equation approach. The materials of the basin and the half‐space are assumed to be the most general anisotropic, homogeneous, linearly elastic solids without any material symmetry (i.e. triclinic). The unknown scattered waves are expressed in terms of three‐dimensional triclinic time harmonic full‐space Green's functions. The results have been tested by comparing the surface response of semi spherical isotropic and transversely isotropic basins for which the numerical solutions are available. Surface displacements are presented for a semicircular basin subjected to a vertical incident plane harmonic pseudo‐P‐, SV‐, or SH‐wave. These results are compared with the motion obtained for the corresponding equivalent isotropic models. The results show that presence of the basin may cause significant amplification of ground motion when compared to the free‐field displacements. The peak amplitude of the predominant component of surface motion is smaller for the anisotropic basin than for the corresponding isotropic one. Anisotropic response may be asymmetric even for symmetric geometry and incidence. Anisotropic surface displacement generally includes all three components of motion which may not be the case for the isotropic results. Furthermore, anisotropic response strongly depends upon the nature of the incident wave, degree of material anisotropy and the azimuthal orientation of the observation station. These results clearly demonstrate the importance of anisotropy in amplification of surface ground motion. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
19.
Marijan Dravinski 《地震工程与结构动力学》1983,11(3):313-335
Scattering of plane harmonic SH, P, SV and Rayleigh waves by several inclusions of arbitrary shape, completely embedded into an elastic half-space, is considered. Perfect bonding between the half-space and the inclusions is assumed. The problem is investigated for linear, isotropic and homogeneous elastic materials. The displacement field is evaluated throughout the elastic medium so that the continuity conditions between the half-space and the inclusions are satisfied in mean-square sense. Numerical results of the surface displacement field are evaluated for single and two elliptic inclusions. The results show the following: (a) presence of a subsurface inhomogeneity may lead to large amplifications of the surface ground motion; (2) different surface displacement patterns emerge for different incident waves; (3) the presence of an additional inclusion may change significantly the surface displacement response of a single inclusion; (4) the surface motion extremes strongly depend upon (i) angle of incidence; (ii) frequency of incident field; (iii) embedment depth of the inclusions; (iv) separation distance between the inclusions; (v) material properties of the half-space and the inclusions; and (vi) location of observation point on the surface of the half-space. 相似文献