共查询到20条相似文献，搜索用时 31 毫秒
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C.A. Stamatopoulos M. Bassanou A.J. Brennan G. Madabhushi 《Soil Dynamics and Earthquake Engineering》2007,27(12):1082-1100
Concentration of damage of buildings near the edge of hard or dense cliff-type topographies has been observed during a number of recent earthquakes. These observations have been interpreted by numerical dynamic analyses that illustrate the amplification of accelerations near the edge of slopes. The paper studies the effect of mitigating these accelerations using anchors both experimentally and numerically. The main issue is that if the part of the slope in which topographic amplification occurs is connected to that in which the acceleration is less, then the accelerations have to become more uniform. The experimental study involves dynamic centrifuge tests at the Cambridge University facility both with and without anchors. The numerical procedure was verified by the seismic response of the centrifuge tests. It was then applied to the study of the effect of anchors of a typical field case, the Aegion slope, under two different input motions. In all cases anchors were found effective in mitigating the seismic motion near the edge. 相似文献
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抗滑桩广泛应用于边坡支护工程,但路桥不稳定边坡抗滑桩对其进行加固时,其在地震作用下的动力响应问题仍未定论。以道真至瓮安高速公路河槽大桥不稳定边坡治理工程为依托,以SIMQKE_GR软件拟合地震设计反应谱,利用FLAC3D有限差分软件建立数值模型,对比地震作用下抗滑桩等支挡结构设立与否对路桥不稳定边坡的动力响应变化规律的影响。结果表明:（1）加速度放大系数无论是沿坡内还是抗滑桩,其值沿竖向均存在一定的震荡变化,但在抗滑桩支护情况下,其震荡幅度明显变小,加速度放大系数变化更平稳。（2）速度放大系数随着高度的增加逐渐减小,未加抗滑桩时速度放大系数在顶层附近出现大幅度波动,添加了抗滑桩的情况下其震荡幅度明显趋缓,变化更稳定。（3）坡体在施加抗滑桩后,治理效果明显,残余位移最大值由无抗滑桩的16.9 cm变为有抗滑桩的1 cm,但最大值均位于边坡表层碎石土和粉质黏土附近。 相似文献
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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
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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
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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7.
Based on the requirement of seismic reinforcement of bridge foundation on slope in the Chengdu-Lanzhou railway project, a shaking table model test of anti-slide pile protecting bridge foundation in landslide section is designed and completed. By applying Wenchuan seismic waves with different acceleration peaks, the stress and deformation characteristics of bridge pile foundation and anti-slide pile are analyzed, and the failure mode is discussed. Results show that the dynamic response of bridge pile and anti-slide pile are affected by the peak value of seismic acceleration of earthquake, with which the stress and deformation of the structure increase. The maximum dynamic earth pressure and the moment of anti-slide piles are located near the sliding surface, while that of bridge piles are located at the top of the pile. Based on the dynamic response of structure, local reinforcement needs to be carried out to meet the requirement of the seismic design. The PGA amplification factor of the surface is greater than the inside, and it decreases with the increase of the input seismic acceleration peak. When the slope failure occurs, the tension cracks are mainly produced in the shallow sliding zone and the coarse particles at the foot of the slope are accumulated. 相似文献
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为了更科学地评价地震荷载作用下土钉支护季节冻土边坡的抗震性能，基于热-动力理论控制方程，应用大型非线性有限元软件ABAQUS，建立带有黏弹性人工边界的地震荷载作用下土钉支护季节冻土边坡的数值模型，对比分析夏季和冬季这两个典型季节时的加速度响应、位移响应以及土钉轴力响应。结果表明：无论是夏季还是冬季，加速度峰值随着季节冻土边坡高程以及激振加速度峰值增加而增加，在夏季时刻的季节冻土边坡坡顶位置处达到最大。此外，在不同地震波峰值加速度作用下，相同位置处的位移响应峰值却有明显的不同，同一地震烈度地震波激震时，夏季的季节冻土边坡坡顶位移最大，表明地震荷载对夏季的季节冻土边坡坡顶破坏效应最为明显，土钉轴力具有高程放大效应和坡面放大效应，季节冻土边坡坡底至坡顶的土钉端部轴力峰值逐渐增大。文中数值模拟模型及结论可为制定地震荷载作用下土钉支护季节冻土边坡抗震设计提供一定的参考。 相似文献
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斜入射地震作用下坡面形态对碎石土边坡稳定性影响研究 总被引：1，自引：0，他引：1
本文研究了在震源近场时,地震波斜入射条件下,不同坡面形态对碎石土边坡稳定性的影响。利用FLAC3D有限差分软件,建立了多种坡面形态的边坡模型。采用对比方法,分析了边坡在地震波作用下的稳定性。结果表明:临空坡面对输入地震波有放大效应;坡面的水平位移与加速度峰值随高度增加而增大,随坡度增加而增大;随着坡面凹度的增大,剪应力增量向坡肩处集中,坡肩愈加不稳定;随着坡面凸度的增大,剪应力增量向坡腰处集中,坡腰愈加不稳定;台阶对坡面的加速度放大效应有削弱作用,台阶数越多越稳定。同时给出了边坡防治的几点建议:减小坡面的坡度;对凹型坡加强坡肩位置处的防治,对凸型坡加强坡腰位置处的防治;对高边坡可设置多级台阶增加稳定性。 相似文献
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在综述国内核电厂高边坡案例研究进展的基础上,以某核电厂含泥化夹层顺层软岩高边坡为例,探讨应用多种方法综合分析其在地震作用下的动态放大效应、抗震性能和加固效果的分析思路。首先,基于典型二维计算剖面,采用拟静力法对边坡进行初步加固设计;然后,基于振动台试验和数值计算,研究边坡动态放大效应、支挡结构的动力响应和抗震性能,探讨边坡抗震参数优化取值。研究结果表明:(1)原位边坡坡面的加速度放大系数随高度增加而增大,且泥化夹层饱水后的放大系数要大于饱水前,水平向最大值为1.90;(2)加固后边坡动态放大系数显著降低,水平最大放大系数为1.31,垂直向基本为1.0,锚索抗滑桩以下边坡基本不存在放大效应,说明软岩高边坡采用锚索抗滑桩和锚索框架抗震性能较好;(3)PGA=0.21g时,边坡整体抗震性能较好,仅最顶部锚杆和中部锚索受力超过设计锚固力,分别超过设计值的20%和5%,适当加强即可;(4)数值计算得到的加速度放大系数分布规律与振动台试验结果较为一致,且两者得到的坡顶加速度放大系数也十分接近。研究成果可为核电厂软岩高陡边坡抗震安全评价和工程设计提供技术支持。 相似文献
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地形效应是地震工程和地震学的重要研究内容.数值方法是研究地形效应的重要工具.然而以往关于地形特征对地形效应的影响的研究大多是基于二维简单模型.对三维真实地形特征和地震动放大的关系缺乏详细的研究.为了更好地描述三维地形特征,本文将地形用不同的地形特征因子来描述,并用算法将它们从地形数据中提取出来.从而使地形和放大系数的相关性的研究转换为不同地形特征因子和放大系数的相关性的研究上.本文中,我们选择芦山地区作为研究对象,用算法提取出特征因子山脊线和坡度.它们分别表征了山脊形态和山体的陡峭程度.我们又用谱元法分别模拟三种不同主频Ricker子波的地震波在起伏地表和水平地表模型中的传播,并得到了它们各自的峰值速度(PGV)放大系数.通过分析三个主频的PGV放大系数在山脊线上分布,我们发现放大系数幅值在山脊线上分布不均匀.放大系数较高的地方位于山脊线弯曲或宽度发生变化的附近.我们又统计了三个放大系数在滑动平均坡度上分布,并得到了放大系数均值和坡度的正相关曲线.结果表明坡度和放大系数两者在幅值分布上具有正相关性. 相似文献
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基于室内试验获取黄土滑坡的静力和动力力学强度参数,建立低角度黄土滑坡破坏大型物理模拟试验模型,结合FLAC3D有限差分软件,分析黄土滑坡的动力响应规律和宏观破坏特性,阐明在地震作用下黄土滑坡的失稳演化规律,揭示黄土滑坡滑体运动迁移路径。结果表明：低角度黄土-泥岩滑坡在地震荷载作用下地震波水平方向和垂直方向均出现明显的放大效应;在黄土层内部,随着斜坡高度增加,坡肩和斜坡后缘加速度放大效应较为明显,对比坡脚、坡腰和坡肩处剖面上加速度放大系数,下伏泥岩对地震波产生一定的放大效应。松弛拉张裂隙,土体强度降低,接触面和坡肩、斜坡后缘处的拉张裂缝形成弧形滑移面,上覆黄土层由内向外依次连带下滑,坡肩处土体的下滑力和地震力促使坡腰土体大面积长距离滑动,最大滑动涉及范围长达200 m左右,土体下滑至坡脚发生堆积并产生隆起。数值模拟结果和振动台试验结果在动力响应和宏观变形破坏特征均呈现较高的吻合度。 相似文献
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An extensive investigation has been made into the interaction between topographic amplification and soil layer amplification of seismic ground motion. This interaction is suggested in the literature as a possible cause for the differences between topographic amplification magnitudes observed in field studies and those obtained from numerical analysis. To investigate this issue a numerical finite element (FE) parametric study was performed for a slope in a homogeneous linear elastic soil layer over rigid bedrock subjected to vertically propagating in-plane shear waves (Sv waves). Analyses were carried out using two types of artificial time history as input excitation, one mimicking the build-up and decay of shaking in the time histories of real earthquake events, and the other to investigate the steady-state response. The study identified topographic effects as seen in previous numerical studies such as modification of the free-field horizontal motion, generation of parasitic vertical motion, zones of alternating amplification and de-amplification on the ground surface, and dependence of topographic amplification on the frequency of the input motion. For the considered cases, topographic amplification and soil layer amplification effects were found to interact, suggesting that in order to accurately predict topographic effects, the two effects should not be always handled separately. 相似文献
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设计并完成比例尺1∶100的边坡振动台模型试验,讨论模型的相似关系、传感器的布置及模型的建造,并编制相应的动荷载加载方案。通过输入不同类型、不同幅值、频率的动荷载,分析模型边坡在地震作用下的动力响应规律以及地震动参数对边坡动力特性和动力响应的影响。试验结果表明,在坡体的表面和坡内的竖直方向上,加速度放大系数均随着高程增加而明显增大。当输入不同压缩比的地震波时,压缩比越大坡体的动力响应越明显,即随着输入动荷载的频率增加,越接近土体的自振频率加速度放大效应越明显;在坡体的同一高程处,坡面的加速度放大系数略大于坡体内的加速度放大系数,表现出一定的趋表效应,同时随着输入地震波振幅的增加,加速度放大系数整体出现递减的趋势。实验结果分析有助于揭示土质边坡在地震作用下的失稳破坏机制,为今后边坡工程的抗震设计提供积极的参考。 相似文献
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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
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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
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设计并完成一个1∶30的大比例尺高陡反倾层状岩质边坡的振动台模型试验,坡体内部有6个软弱泥化夹层,研究在组合支护体系作用下EL Centro地震波和汶川-清屏地震波激振下泥化夹层含水量发生变化时边坡的加速度动力响应规律。试验结果表明:(1)坡面X、Z向加速度放大系数均具有非线性高程放大效应,但前者大于后者;(2)泥化夹层含水量的变化对坡面加速度放大效应影响显著,注水后X向减小而Z向增大;(3)支护体系作用下边坡临空面放大效应的现象受限制,预应力锚索抗滑桩以下边坡基本不存在加速度放大效应;边坡分级支护可有效降低X向加速度放大系数的高程增大效应,但对Z向会产生不利作用;(4)边坡的破坏模式为上部受软弱夹层滑动牵引而发生倾倒-拉裂变形,导致顶部框架梁有可能最先发生破坏,且破坏类型可能以绕坡顶为支点向坡体内侧转动,引起上部的锚索产生拔出破坏。 相似文献
18.
Olga-Joan Ktenidou Francisco-J. Chávez-García Dimitrios Raptakis Kyriazis D. Pitilakis 《Bulletin of Earthquake Engineering》2016,14(3):623-645
We study site effects using 520 weak motion earthquake records from a vertical array in Aegion, Greece. The array is inside a basin, has four stations in soil, and one in bedrock (178 m depth). The site is marked by high seismicity and complex surface geology. We first use the records to establish the downhole accelerometer orientations and their evolution with time. Then we estimate site effects using empirical spectral ratios with and without a reference site (standard and horizontal-to-vertical spectral ratio). We find significant site amplification which cannot be accounted for by 1D model predictions, along with a significant difference in the amplification level between the two horizontal components. These are indications of 2D effects, namely surface waves generated at the basin edge. The difference in amplification between the horizontal components is maximised when these are rotated with respect to the orientation of the basin edge. The strongest amplification takes place in the direction parallel to the basin edge (SH, or out-of-plane motion), and is up to 2 times higher than in the perpendicular direction (SV, or in-plane motion). This directional effect on the amplification is corroborated by numerical 2D modelling using incident SH and SV waves, with the former possibly generating strong Love waves. In the records, the directionality is clear for windows containing the largest amplitudes of the records (S waves and strong surface waves), while it tends to vanish for coda-wave windows. This directionality is also observed when using response spectral ratios rather than Fourier ratios. We compute soil-to-rock amplification factors for peak ground acceleration (PGA) and find it is significantly higher than what is predicted by current design codes. We attribute this difference to the basin edge amplification, linear soil behaviour, and to the inability of simple scalar values like PGA to describe complex amplification effects. Finally, we analyse the earthquake records at a surface station near the slope crest and do not observe significant topographic amplification. 相似文献
19.
Roberto Paolucci 《地震工程与结构动力学》2002,31(10):1831-1853
The problem of amplification of seismic waves by surface topographic irregularities is addressed through analytical and numerical investigations. First, a closed‐form expression for estimating the fundamental vibration frequency of homogeneous triangular mountains is obtained, using Rayleigh's method. Subsequently, numerical modelling based on the spectral element approximation is used to study the 3D seismic response of several real steep topographic irregularities excited by vertically propagating plane S‐waves. A topographic amplification factor is obtained for each case, by a suitable average of the ratio of acceleration response spectra of output vs input motion. The 3D amplification factors are then compared with those derived by 2D analyses as well as with the topographic factors recommended in Eurocode 8 for seismic design. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
20.
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