共查询到20条相似文献，搜索用时 31 毫秒
1.
地形对地震动的影响比较复杂, 考虑地形放大效应的地震滑坡稳定性分析需要选择合适的地震动参数. 本文使用自贡地形影响台阵记录到的2008年汶川MS8.0地震主震加速度记录, 分析了地震动峰值加速度、 阿里亚斯烈度以及90%能量持时随地形高度的变化, 探讨了地形效应作用下峰值加速度和阿里亚斯烈度与地震动作用下斜坡稳定性的相关性. 结果表明: ① 地形场地对峰值加速度和阿里亚斯烈度均有显著的放大效应. 地形放大效应较为复杂, 其整体上随台站高度的增加而增大, 水平向的放大效应大于竖直向. 水平向峰值加速度的放大系数为1.1—1.8, 阿里亚斯烈度的放大系数为1.2—3.3; 竖直向相应放大系数分别为1.1—1.3和1.2—1.7. ② 地形对地震动持时也有一定的放大效应, 但不同高度、 不同分量的放大效应没有显著差异, 其放大系数均约为1.3. ③ 阿里亚斯烈度和峰值加速度均能很好地表征地形对地震动的影响, 与地震动对斜坡稳定性的影响具有很强的相关性. 与峰值加速度相比, 阿里亚斯烈度综合了地震动的多方面特征, 可以更好地表征地形对地震动的影响, 与地震动作用下斜坡稳定性的相关性更强. 相似文献
2.
Dominic Assimaki Eduardo Kausel George Gazetas 《Soil Dynamics and Earthquake Engineering》2005,25(7-10):513-527
During the 1999 Athens Earthquake the town of Adàmes, located on the eastern cliff of the Kifissos river canyon, experienced unexpectedly heavy damage. Despite the significant amplification potential of the slope geometry, topography effects cannot alone explain the uneven damage distribution within a 300 m zone behind the crest, characterized by a rather uniform structural quality. This paper illustrates the important role of soil stratigraphy, material heterogeneity, and soil–structure interaction on the characteristics of ground surface motion. For this purpose, we first perform elastic two-dimensional wave propagation analyses utilizing available geotechnical and seismological data, and validate our results by comparison with aftershock recordings. We then conduct non-linear time-domain simulations that include spatial variability of soil properties and soil–structure interaction effects, to reveal their additive contribution in the topographic motion aggravation. 相似文献
3.
基于曲线网格有限差分方法研究了地震波在不同坡度的山体地形及水平地表模型中的传播,得到了各模型速度波形及地表峰值速度特征,从地形自身特征及震源特征两方面出发讨论了地形效应:一是相同的震源模型下地形坡度、形状对地震动的影响;二是同一山体模型下地震动对不同震源机制的点源以及相对复杂的有限断层的响应.主要结论如下:(1)一般情况下,地形放大效应在坡度较大的地方比较明显,并随着坡度的增加而增大,但在某些特定情况下,放大效应与坡度并不满足正相关,且这种情况的发生与震源性质无关,可能仅受地形形态自身的影响;(2)对于不同的震源机制,地面运动各分量受地形影响程度不同,总体上水平分量受地形影响程度更大;(3)震源机制和震源激发的波的频率会影响放大效应最大值出现的位置,放大效应最大值不一定出现在山顶处,有可能会出现在起伏地形的震源对侧,出现位置可能与波的相互作用有关;(4)有限断层模型下,地面运动特征相对更为复杂,地形效应不仅受断层模型几何特征的影响,同时断层破裂过程对其也有着重要的影响. 相似文献
4.
George D. Bouckovalas Achilleas G. Papadimitriou 《Soil Dynamics and Earthquake Engineering》2005,25(7-10):547-558
This paper presents results of numerical analyses for the seismic response of step-like ground slopes in uniform visco-elastic soil, under vertically propagating SV seismic waves. The aim of the analyses is to explore the effects of slope geometry, predominant excitation frequency and duration, as well as of the dynamic soil properties on seismic ground motion in a parametric manner, and provide qualitative as well as quantitative insight to the phenomenon. Among the main conclusions of this study is that this kind of topography may lead to intense amplification or de-amplification variability at neighboring (within a few tens of meters) points behind the crest of the slope, especially for high frequency excitations. Nevertheless, a general trend of amplification near the crest and de-amplification near the toe of the slope seems to hold for the horizontal motion. As a result of these two findings, it becomes evident that reliable field evidence of slope topography aggravation is extremely difficult to establish. Furthermore, this study highlights the generation of a parasitic vertical component of motion in the vicinity of the slope, due to wave reflections at the slope surface, that under certain preconditions may become as large as the horizontal. Criteria are established for deciding on the importance of topography effects, while approximate relations are provided for the preliminary evaluation of the topographic aggravation of seismic ground motion and the width of the affected zone behind the crest. 相似文献
5.
土-结构相互作用效应对结构基底地震动影响的试验研究 总被引：3，自引：0，他引：3
利用土与结构动力相互作用振动台模型试验数据,通过各种试验工况下土层表面与基础表面加速度反应的比较,深入探讨了土与结构动力相互作用效应对高层建筑结构基底地震动的影响。从输入地震动频谱特性、输入地震动强度水平和上部结构动力特性3个方面详细分析了与SSI效应对高层建筑基底震动影响程度有关的一些因素。结果表明：SSI效应对高层建筑基底地震动的影响与输入地震波的动力特性有很大关系。在地震动的频谱成分方面,SSI效应对高层建筑基底地震动的影响主要体现为土层表面和基础表面在与输入地震动卓越频率相近处的频谱成分有较大差异;SSI效应对高层建筑基底地震动的影响程度随着输入加速度峰值水平的增加而减小;在某一特定地震波作用下,当上部结构的振动频率与地震地面运动的卓越频率相近时,SSI效应对高层建筑基底地震动的影响较为强烈。 相似文献
6.
斜坡动力响应特征与斜坡形态密切相关,若入射地震波主频接近斜坡卓越频率就会放大斜坡动力响应,甚至造成斜坡失稳。汶川地震对远离震中的黄土地区造成了较为严重的破坏,局部场地震害和地震动放大效应显著。选取汶川地震典型黄土斜坡场地,利用地形台阵流动观测和数值模拟计算相结合的方法,系统开展强震动作用下黄土斜坡场地动力响应特征研究。结果表明:坡顶卓越频率最小,其PGA放大系数甚至达到坡底的1.98,这种现象可能与斜坡高差和入射波波长之比密切相关,比值0.2时坡顶放大效应达到最大。随斜坡坡度增加,放大效应增强,坡顶反应谱卓越周期放大系数可达5,说明斜坡地形对强震地面运动有显著影响。数值计算结果与实际强震观测基本吻合,其结果对黄土地区建设工程抗震设防具有重要的科学与实际意义。 相似文献
7.
不规则地形和土层对地震动的影响较大,建(构)筑物选址及其抗震设防必须考虑地形和土层场地的放大效应,以避免或减轻其震害.利用自贡地形台阵记录的汶川地震(Ms8.0)的主震加速度时程,基于传统谱比法分别研究了地形和土层场地对地震动的放大效应.结果表明:(1)地形场地在低频的放大效应不明显,最大仅为1.24;在高频的放大效应较显著,在1~10 Hz频带,山顶的放大效应最大,EW、NS和UD地震动的最大放大效应分别为4.15、3.61和2.41,对应频率分别为5.72 Hz、6.46 Hz和7.44 Hz;在10~20 Hz频带,靠近山顶的山脊上某个地震动分量的放大效应最大,7#台站EW、5#台站NS和7#台站UD地震动的最大放大效应分别为9.10、5.56和2.52,对应频率分别为16.97 Hz、16.91 Hz和17.91 Hz.(2)地形场地的最大放大效应随高度有增加的趋势,且在0.1~10 Hz频带随高度增加的趋势更加明显.(3)土层场地水平向地震动在2 Hz以上开始明显放大,竖向地震动在4 Hz以上开始明显放大;EW、NS和UD地震动的最大放大效应分别为13.4、12.168和6.0,对应频率分别为6.94 Hz、7.55 Hz和10.8 Hz.(4)土层场地与地形场地的最大放大效应相比较,前者显著大于后者,对于水平向地震动,前者至少是后者的3倍以上;对于竖向地震动,前者至少是后者的2.5倍以上.(5)无论是地形场地还是土层场地,地震动的最大放大效应均有水平向大于竖向的特征. 相似文献
8.
The response of an elastic circular wedge on a flexible foundation embedded into a half-space is investigated in the frequency domain for incident pane SH-waves. The problem is solved by expansion of the motion in all three media (wedge, foundation and half-space) in cylindrical wave functions (Fourier-Bessel series). The structural model is simple, but accounts for both differential motions of the base and for the effects of soil-structure interaction. Usually, structural models in earthquake engineering consider either differential ground motion, but ignore soil-structure interaction, or consider soil-structure interaction, but for a rigid foundation, thus ignoring differential ground motion. The purpose of the study is to find how stiff the foundation should be relative to the soil so that the rigid foundation assumption in soil-structure interaction models is valid. The shortest wavelength of the incident waves considered in this study is one equal to the width of the base of the wedge. It is concluded that, for this model, a foundation with same mass density as the soil but 50 times larger shear modulus behaves as ‘rigid’. For ratio of shear moduli less than 16, the rigid foundation assumption is not valid. Considering differential motions is important because of additional stresses in structures that are not predicted by fixed-base and rigid foundation models. 相似文献
9.
山地丘陵地形对地震动的分布有重要的影响,研究地形效应,有利于充分认识地震灾害风险,为减轻灾害损失做好防御措施。基于实际地形建立自贡西山公园观测台阵所在山体的三维有限元模型,研究开发黏弹性人工边界和SH波垂直入射前处理程序,开展动力学数值模拟;数值模拟结果与实际记录进行对比,并验证模型的合理性;研究分析低山丘陵山体对地震动强度及空间分布影响,以及峰值加速度与入射波频率、高程、坡度的关系。结果表明：低山丘陵山顶位置地震动峰值放大明显,而山脚凹陷位置地震动峰值存在削弱现象;地形效应与输入地震动频率密切相关,不同主频的输入地震动所造成的地表峰值加速度分布不同;较高主频的地震动可以凸显地形细节的影响;地表峰值加速度与高程具有较好的正相关关系,与坡度的相关关系较弱。综合高程和坡度拟合峰值加速度的效果优于仅使用高程或坡度的拟合,二元三次多项式拟合效果较好,可用于定量描述地形放大系数随高程和坡度的变化。 相似文献
10.
Three studies of site amplification factors, based on the recorded aftershocks, and one study based on strong motion data, are compared one with another and with the observed distribution of damage from the Northridge, CA, earthquake of 17 January 1994 (ML=6.4). In the epicentral area, when the peak ground velocities are larger than vm≈15 cm/s, nonlinear response of soil begins to distort the amplification factors determined from small amplitude (linear) wave motion. Moving into the area of near-field and strong ground motion (vm>30 cm/s), the site response becomes progressively more affected by the nonlinear soil response. Based on the published results, it is concluded that site amplification factors determined from small amplitude waves (aftershocks, small earthquakes, coda waves) and their transfer-function representation may be useful for small and distant earthquake motions, where soils and structures respond to earthquake waves in a linear manner. However in San Fernando Valley, during the Northridge earthquake, the observed distribution of damage did not correlate with site amplification determined from spectra of recorded weak motions. Mapping geographical distribution of site amplification using other than very strong motion data, therefore appears to be of little use for seismic hazard analyses. 相似文献
11.
W. D. Liam Finn E. Zhai T. Thavaraj X. -S. Hao C. E. Ventura 《Soil Dynamics and Earthquake Engineering》2003,23(4):323-329
The 1996 Duvall earthquake in Washington State triggered ground motion stations in the Fraser Delta, British Columbia, located on varying depths of Holocene and Pleistocene soils to a maximum depth of 800 m and one station on bedrock. Recorded ground motions were used to examine the applicability of 1-D and 2-D site response analyses for amplification studies in the Delta. 1-D response analysis gave a good indication of the period of peak response. Response spectra computed by 1-D analysis did not compare well with recorded spectra except at very deep sites. The use of 2-D analyses to include buried topography generally improved the predictions of site response spectra at the shallow sites. However, for the shallow earth sites, the recorded motions showed a strong spectral response at short periods in the range of 0.1–0.25 s. Neither 1-D nor 2-D analysis predicted this response. 相似文献
12.
地震动作为引起地震灾害的原动力,常常通过造成建筑物倒塌、山体滑坡等形式引起大量人员伤亡和财产损失。1920年海原8½级地震,在震中距80 km远的西吉—静宁交界的黄土丘陵区引发了大量的山体滑坡,并造成重大人员伤亡和财产损失。在分析海原地震高烈度区滑坡分布特征的基础上,通过场地调查和数值计算等方法,研究典型滑坡密集场地的地质条件及地震反应特征。研究表明起伏地形和黄土厚度不均等因素造成丘陵山体两侧地震反应的差异,从而导致地震滑坡在斜坡土体较厚的一侧成群连片发育。海原地震造成的滑坡密集区的地形地貌、岩土性质、土层结构等条件决定了该地区地震动随局部场地条件变化非常迅速,地层场地效应和地形场地效应联合作用加剧了斜坡地表的地震动放大作用,增加了触发地震滑坡的动力。 相似文献
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14.
Antiplane response of a dike with flexible soil-structure interface to incident SH waves 总被引：2，自引：0，他引：2
Abdul Hayir Maria I. Todorovska Mihailo D. Trifunac 《Soil Dynamics and Earthquake Engineering》2001,21(7)
Studies of the effects of differential ground motions on structural response generally do not consider the effects of the soil-structure interaction. On the other end, studies of soil-structure interaction commonly assume that the foundation of the structure (surface or embedded) is rigid. The former ignore the scattering of waves from the foundation and radiation of energy from the structure back to the soil, while the latter ignore quasi-static forces in the foundations and lower part of the structure deforming due to the wave passage. This paper studies a simple model of a dike but considers both the soil-structure interaction and the flexibility of the foundation. The structure is represented by a wedge resting on a half-space and excited by incident plane SH-waves. The structural ‘foundation’ is a flexible surface that can deform during the passage of seismic waves. The wave function expansion method is used to solve for the motions in the half-pace and in the structure. The displacements and stresses in the structure are compared with those for a fixed-base model shaken by the free-field motion. The results show large displacements near the base of the structure due to the differential motion of the base caused by the wave passage. 相似文献
15.
现有大量观测记录表明:斜坡地形对地震波的传播有着非常强烈的影响。为服务于工程抗震设计,基于显式有限元方法,定量分析SH波垂直入射下二维斜坡地形的地震动响应与斜坡角度、土层厚度以及介质阻抗比的关系,总结了位于一维土层基本频率附近斜坡上台面各区域放大因子的变化规律。研究表明:（1）斜坡面对SH波的反射使二维斜坡地形的放大倍数较一维土层存在显著放大,且该现象在缓坡中更加明显。（2）当土层厚度为斜坡高度的1/4,介质阻抗比为0.368,坡度为30°时,放大因子在距坡顶1.67倍斜坡高度处取到最大值1.930。（3）斜坡覆盖土层薄时,放大因子受斜坡角度的影响大,斜坡覆盖土层厚时,阻抗比成为影响放大因子的主要因素。（4）分别考虑土层厚度、斜坡角度、介质阻抗比以及观测点位置对二维斜坡地形地表地震动响应的影响,取1倍斜坡高度作为区域间隔,统计每个区域内各参数对应的放大因子最大值,对比现有规范给出工程抗震设计参考值及放大因子大于1的基频比范围。 相似文献
16.
Topographic site effects of Xishan Park ridge in Zigong city,Sichuan considering epicentral distance
Ma Qiang Wang Fuchen Tao Dongwang Xie Quancai Liu Heyi Jiang Peng 《Journal of Seismology》2021,25(6):1537-1555
Ground motion amplification induced by topography plays a vital role in engineering seismology. A topographic array of 8 accelerographs has been operating along the ridge in Xishan Park since 2007. The topographic site effects in Zigong city are studied based on the strong motion data of 2008 Ms 8.0 Wenchuan earthquake (the epicentral distance?=?225 km) and 2019 Ms 5.2 Zizhong earthquake (the epicentral distance?=?29 km). We compare the peak ground acceleration (PGA) of the two earthquakes and find that the PGA of Station 7#, which locates on a relatively steep slope, is amplified by 4.41 times comparing with the reference station in Zizhong earthquake, while this value is only 1.62 in Wenchuan earthquake. Fourier amplitude spectrum shows that the high frequency content of Zizhong earthquake is more abundant because of its smaller epicentral distance. By using the standard spectral ratio (SSR) method, we conclude that the amplification occurs because high-frequency ground motion is likely to resonate at small-scale features. Finally, the 3D numerical simulations are used to verify these conclusions. Our work indicates that more sophisticated numerical models need to be established for more accurate topographic site effects quantification. In addition, the influence of nearby topographic features should be considered when selecting reference stations.
相似文献17.
The distortions of earthquake ground motions recorded in small instrument shelters as a result of soil-structure interaction effects are investigated by means of a theoretical parametric study. A total of 12 foundation geometries varying in basal radius, embedment depth and extension above the ground surface and a number of soil profiles including uniform and layered soil models were considered. The results obtained show significant amplification and deamplification of the free-field ground motion for sufficiently soft soils (β<200 m/sec) and sufficiently high frequencies (f>20 Hz). 相似文献
18.
近断层地震动中长周期、短持时和高能量的加速度脉冲将对高层摩擦摆基础隔震结构的减震性能产生不利影响,考虑土-结构相互作用（SSI效应）后的隔震结构将产生动力耦合效应,可能进一步放大隔震结构地震响应。为此,通过一幢框架-核心筒高层摩擦摆基础隔震结构的非线性地震响应分析,考察近断层脉冲型地震动作用下框架-核心筒摩擦摆基础隔震结构的层间位移角、楼层加速度和隔震层变形等响应规律,揭示隔震体系的损伤机理。基于集总参数SR （sway-rocking）模型,分析不同场地类别与不同地震动类型对隔震体系动力响应影响规律。结果表明:高层摩擦摆基础隔震结构在近断层脉冲型地震动作用下的减震效果相比普通地震动减震效果变差,楼层剪力、层间位移角和隔震层变形等超越普通地震动作用下的1.5倍;对于Ⅲ和Ⅳ类场地类别,考虑SSI效应使隔震结构的地震响应进一步放大,弹塑性层间位移角随着土质变软增大尤为明显。 相似文献
19.
采用基于ABAQUS平台的显式有限元动力学分析方法,结合人工黏弹性边界理论,研究了局部凸起地形对地震动特性(包括反应谱、峰值加速度、峰值速度和峰值位移等)的影响,分析了台地宽度对地形放大效应的影响.结果表明:凸起地形平台段空间点地震动受地形效应影响较大,在零阻尼条件下,其谱比曲线呈双峰特点,.8—0.9s的中长周期段谱比达到一个较大值1.6,在0.08—0.09s的高频段谱比超过2.0,且最大值出现在平台中点;对于凸起地形斜坡段,在大部分周期点处,顶点的谱比高于其它斜坡点,而且在周期超过0.4s的频段,斜坡段观测点的谱比表现出较明显的规律性,即越靠近顶点的观测点,其谱比值越大;坡底段地表不同观测点的谱比基本在脚点与计算边界点(人工边界点)对应的谱比值之间变化,在不同的频段均表现出较明显的规律性.凸起地形平台段宽度对地震动高频成分的放大效应具有较大影响,但只局限在一定的宽度范围内,随着宽度的增大,其对地形放大效应的影响逐渐减弱. 此外,台地宽度的变化对地震动峰值加速度的放大效应有一定的影响,而对峰值速度、峰值位移的放大效应的影响则不明显. 相似文献
20.
The free-field accelerograms along Feitsui Canyon are analyzed and modeled by a numerical scheme to study the effect of canyon topography. Since six strong-motion accelerometers (SC1–SC6) were deployed along the Feitsui Canyon in 1991; there are 14 earthquakes (4.9≤ML≤6.6) recorded by these stations until June 1996, but only five triggered all six stations. The maximum PGA value is 68.6 cm s−2 recorded at station SC1. According to the present data, the effect of the dam on the ground motions at canyon stations can be negligible. The amplitude of ground motion on the slopes of the canyon is bigger than that at its trough. The integral equation method is applied to a two dimensional model of Feitsui Canyon to study the effects of the canyon topography. We choose the ground motion of SC3 or SC4 station at the trough of the canyon as the input motion for the model, which is then used to predict the ground motion at the other five stations. Apart from the earthquake close to the damsite, the simple model can reproduce the observed accelerations at all frequencies below 4 Hz. Overall, the numerical method can well predict the ground motion along the canyon, although the high-frequency simulation is underestimated. 相似文献