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削山造地后形成的黄土高填方场地对地震动参数特性影响较大。以实际工程项目为研究对象,构造不同填土高度的计算剖面,采用一维等效线性化方法计算土层地震动参数,分析基岩地震动输入参数和填土高度对场地地表放大效应的影响。研究表明:场地地震放大系数随填土层的高度增加呈递减趋势。在多遇地震动和基本地震动作用下,场地地震放大系数递减速度比罕遇地震动和极罕遇地震动作用下要大。当填土高度达到一定程度后放大效应趋于平稳;填土高度的变化,会改变地表加速度反应谱的形状。填土高度越大,地表反应谱长周期的频谱成分越显著,反应谱曲线向后移,反应谱峰值点均明显向长周期移动,并出现多个峰值点,反应谱特征周期值变大;下伏基岩的刚度越大,地表峰值加速度的放大效应越大。地表加速度反应谱特征值相比变小。当填土高度增大到一定程度时,下伏基岩的种类对地表地震动特性影响则不明显。该研究成果对高填方场地的地震安全评价和结构抗震设计提供参考。 相似文献
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首先建立了青藏高原东北地区的地震烈度衰减关系，然后以美国西部地区作为参考地区，在霍俊荣数据的基础上，增加了近年来得到的部分强震记录，采用反映高频地震动震级饱和与近场饱和特征的衰减关系模型，统计得到了美国西部地区水平向基岩加速度峰值与短周期反应谱衰减关系. 与用美国南加州数字宽频带记录建立的美国西部长周期加速度反应谱衰减关系结合，得到了美国西部周期0.04~6 s的反应谱衰减关系. 采用转换方法，得到了青藏高原东北地区水平向基岩加速度峰值与反应谱衰减关系. 相似文献
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地铁隧道群对地震动的放大作用 总被引：1，自引：0，他引：1
本文采用有限元方法在时域内研究了基岩上均匀场地中隧道群对地震动的放大作用,分析了隧道间距、人射地震波频谱等因素对隧道群附近地表地震动反应谱的影响.研究表明,隧道群对地震动具有显著的放大作用,放大作用的大小与隧道间距和人射地震波频谱有着密切关系;隧道之间存在相互作用,加速度峰值的最大值多大于单隧道情况,且水平加速度峰值的... 相似文献
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工程场地岩土条件是影响地震动峰值加速度的主要因素之一.设基岩输入面的地震动峰值加速度为ar,经场地土层反应分析求得的地震动峰值加速度为aks,则场地土层地震动峰值加速度放大因子ks可由ks=aks/ar求得.
作为工程地震学的一个统计量,ks表征场地土层放大综合效应. 相似文献
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渤海海域软土层土对场地设计地震动参数取值具有显著影响。选取渤海中部钻孔剖面作为计算场地模型基础,分别构建软土和硬土场地模型,并通过改变软土层厚度,构造新的场地模型。采用等效线性化方法（EL法）和非线性计算方法（NL法）分别对场地模型进行地震反应分析,分析了海底软土层土对地震动参数的影响。研究结果表明:海底软土层土对地震动峰值加速度的影响显著,随着地震动输入增加,软土层放大效应减弱,减震作用逐渐增强;EL法中,软土层土对基岩反应谱的高频部分具有明显滤波作用,而NL法中,滤波作用较弱,海底面反应谱随地震动输入的增大先放大后减小;软土层土会降低设计地震动地震最大影响系数,增大特征周期。对于海域工程,特别是深基础工程抗震设计地震动参数的确定,从保守角度考虑,建立场地模型时建议删除软土层。 相似文献
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选用广东省980个满足中硬场地土条件的地震钻孔资料,对每一个工程场地合成9组相互独立的基岩加速度输入时程,进行土层地震反应分析,对各个工程场地地面与基岩地震动峰值加速度的对应关系进行研究,结果表明Ⅵ度区的工程场地地面与基岩地震动峰值加速度的比值为1.376,VII度区为1.368,VIII度区为1.341,平均均方根误差为0.067。 相似文献
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通过对甘肃省158个场地安全性评价结果的分析,讨论了不同的超越概率下水平地震动峰值加速度之间的关系以及不同的场地条件对基岩峰值加速度的放大效应。结果对甘肃地区地震安全性评价中水平地震动峰值加速度的取值提供必要的参考。 相似文献
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The strong ground motion produced by the 17 October, 1989 Loma Prieta earthquake in northern California was recorded at over 100 stations. Accelerograms were generated at sites with significantly different geology, including land fill and soft sedimentary soil sites. In this study, the attenuation characteristics of the peak vertical and horizontal ground accelerations are studied for freefield recording conditions within 100 km of the source by the application of a non-linear multi-regression procedure. Two sets of attenuation models for weighted and unweighted observations are compared with those reported by other investigators for this earthquake and for regional and worldwide data. The peak ground acceleration (PGA) observations for this earthquake exceed previous predictions of standard attenuation models, particularly beyond 30 km (approximately 60 percent at 50 km). Higher attenuation of the vertical component compared to the horizontal is confirmed. The regression considers site geology as an independent parameter. Soil sites display as much as 23 per cent amplification relative to rock sites for horizontal PGA and as much as 40 per cent for vertical PGA. Amplification of the ground motion at sites characterized by soft soil geology is examined by comparing the recorded PGA with the corresponding prediction at sites underlain by stiff soil. Eight of ten of the soft soil sites display significant amplification relative to stiff soil sites (as much as 300 per cent for horizontal and 200 per cent for vertical components). Particular attention is paid to the so-called anomalous observations at distances beyond 50 km. The anomalous observations between 50 and 80 km may be attributed to various factors such as geology, basic geometry, azimuthal dependence, source mechanism and normal scatter of observations. 相似文献
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最大峰值加速度与有效峰值加速度的大小比例关系及影响因素探讨 总被引：1，自引：0，他引：1
分别以最大峰值加速度(以下简称PGA)和有效峰值加速度(以下简称EPA)为参数,对金沙江流域上12个工程场点进行了地震危险性分析,得到了各个场点在不同的年超越概率下的基岩PGA和EPA值。通过对PGA、EPA值比较分析认为:PGA与EPA值的大小比例关系主要受年超越概率大小的影响,当年超越概率较大时,表现为PGA>EPA;当年超越概率较小时,PGA与EPA的比例关系还与场点周围的潜源分布形式及潜源的震级上限的大小有关,不同的年超越概率、不同的潜源分布形式和震级上限,可使PGA>EPA,也可使PGA相似文献
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In this paper, a statistical study based on thirty-two strong rock motions is presented for the dynamic base shear of buildings on three different sites representing stiff soil, deep cohesionless soil and soft clay conditions. A short and squatty building and a tall and slender building are selected. For each building height, frame, wall and shearwall–frame systems are considered. It is found that short and squatty frame systems have the largest base shear. As for buildings on rock, the response of buildings on stiff and deep cohesionless soil conditions depends on the peak horizontal acceleration and peak horizontal velocity of the rock motion. Furthermore, the soil–structure interaction which affects only the stiff structures is found to reduce the dynamic base shear. 相似文献
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STUDY ON DYNAMIC RESPONSE AND INSTABILITY OF SOIL-ROCK MIXTURE DEPOSIT WITH DIFFERENT STONE CONTENTS AND SLOPE GRADIENTS 
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下载免费PDF全文 Soil-rock mixture deposit is an extremely heterogeneous loose rock-soil deposit formed since Quaternary, which is composed of blocks, fine-grained soil and pore with a certain engineering scale and high strength and has a certain stone content. These soil-rock mixtures accumulated on slopes have been completely destroyed and their mechanical strength is very low. They are widely distributed in the mountainous areas of Southwest China, which poses a great threat to the engineering. Earthquakes occur frequently in Southwest China, and the instability of soil-rock mixture deposit under seismic load is one of the important factors causing the damage to this type of deposit. The dynamic response of soil-rock mixture deposit under seismic load is an important index to study its instability mechanism under seismic load.
Based on indoor shaking table model test, the influence of rock content and slope gradient on dynamic response characteristics of soil-rock mixture deposit was studied. In model tests, rock content is 30%, 40% and 50%respectively, and slope gradient varies from 20°, 30° and 40°. Two different seismic loading frequencies and three different excitation strengths were given. The peak acceleration(PGA)amplification coefficients in horizontal and vertical directions of soil-rock mixture deposit were analyzed under the change of rock content and slope gradient. The permanent displacement and deformation law of the top and foot of the slope of soil-rock mixture deposit were analyzed by model test. The experimental results show that the dynamic acceleration response characteristics of the soil-rock mixture deposits at the top and foot of the slope are different under different slope gradients and rock content conditions, and the horizontal PGA amplification coefficients of the soil-rock mixture deposits are also different. With the same seismic frequency and excitation intensity, the horizontal PGA amplification coefficient increases with increased slope gradient, and the rate gets faster. With the increase of stone content, the magnification coefficient of horizontal PGA decreases, and the higher the stone content, the slower the decrease rate of horizontal PGA magnification coefficient. When the slope gradient of soil-rock mixture deposit increases, the corresponding horizontal and vertical PGA amplification coefficients increase with the same seismic frequency and excitation intensity. The amplification coefficients of PGA in the vertical direction are different, but the overall magnification is weaker than that in the horizontal direction. The vertical PGA amplification coefficients of the foot, middle and lower parts of the slope are larger, while the vertical PGA amplification coefficients of the upper and middle parts of the slope tend to decrease. The higher the frequency of seismic wave is, the smaller the vertical PGA amplification coefficient corresponding to the same elevation will be, which indicates that the vertical PGA amplification coefficient is negatively correlated with the elevation. The variation trend of PGA magnification coefficient of soil-rock mixed deposit in vertical direction is different with the change of stone content. Under the same excitation intensity, the larger the slope gradient is, the larger the permanent displacement at the top of the slope will be, and the larger the rock content, the smaller the corresponding displacement at the top of the slope. The permanent displacement of the top of the slope is obviously larger than that of the foot of the slope, which indicates that the magnification effect of the top of the slope is obvious. After the vibration process and sliding of the landslide, the large-sized particles in the soil-rock mixture deposit move downward faster and slip on the surface of the deposit body. There was a very obvious phenomenon of particle sorting in the pile-up at the foot of the landslide body. The results of this study are of practical significance for the analysis of the dynamic response law of soil-rock mixture deposit under seismic load due to the change of rock content and slope gradient. 相似文献
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汶川地震远场地震动特征及其对长周期结构影响的分析 总被引：5，自引：0，他引：5
汶川8．0级大地震中,中国数字强震动台网获得了大量的数字强震动记录,这些记录特别是远场记录具有丰富的长周期地震动分量。本文根据东南强震动中心获取的区域数字强震动记录,分析汶川8．0级地震的远场地震动特征,研究了基岩场地及深厚软弱场地的长周期地震动及其差异;根据长周期结构的特点,选取建于深厚软弱场地上的江苏A050强震台的超长地震记录进行结构地震反应分析,研究汶川8．0级地震对远场长周期结构的影响,并结合实际震害特点,提出了长周期结构抗震及地震安全对策中一些值得注意和思考的问题。 相似文献
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地基条件和墙高是影响挡土墙地震响应特征的重要因素。建立不同地基条件的仰斜式挡土墙有限元时程分析模型，以墙身外倾最大危险状态为最不利时刻，研究地基条件和墙高对挡墙动力响应及墙-土相互作用的影响特征，并以满足力学检算和墙身位移限值为出发点，提出同时考虑地基条件和地震峰值加速度PGA的仰斜式挡墙墙高控制建议。结果表明：岩质地基挡墙墙背动土压力沿墙高呈中部大、上下小的凸形分布，大震下土压力较中震时有小幅减小；基底反力呈墙踵为0、墙趾集中的三角形图式，且随PGA和墙高的增加踵部脱空趋势更为明显；土质地基挡墙因墙底地基土变形对墙后填土的牵连作用，填土跟随墙身运动的趋势加剧，墙背动土压力与PGA呈正相关并沿墙高近似呈线性分布，于墙底处最大；墙身往复摆动使踵趾端地基土体塑性变形较基底中部明显，基底反力峰值向中部转移；根据最不利时刻稳定性、承载力检算，考虑对墙身位移合理限制，提出地震区仰斜式挡墙的允许墙高在设防PGA不超过0.2g时为8 m, 0.4g大震下硬质岩地基挡墙可达8 m,软质岩地基挡墙不宜超过6 m,碎石土、砂质黏土地基挡墙不宜超过4 m。 相似文献
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该研究在温州两个深软土层场地上完成了剪切波速测试误差专项实验，统计拟合了误差分布规律并研究了其对PGA的影响，得到结论:每米深度上的实测误差基本符合标准正态分布，温州地区深软场地的测试误差与我国其他几个地区覆盖土层较浅场地上的每米实测误差程度基本相同；两个场地上各深度的误差标准差大致相同，约为16%；实测误差对PGA影响明显，误差取1倍标准差时PGA的变化程度可能达到30%，取2倍标准差时可能高达45%；PGA的变化程度受输入地震动的频率特性制约，长周期频率成分对深软场地计算结果的影响明显。 相似文献
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In order to propose a seismic design spectrum that includes the effect of rupture directivity in the near-fault region, this study investigates the application of equivalent pulses to the parameter attenuation relationships developed for near-fault, forward-directivity motions. Near-fault ground motions are represented by equivalent pulses with different waveforms defined by a small number of parameters （peak acceleration, A, and velocity V; and pulse period, Tv）. Dimensionless ratios between these parameters （e.g., ATv/V, VTv/D） and response spectral shapes and amplitudes are examined for different pulses to gain insight on their dependence on basic pulse waveforms. Ratios of ATv/V, VTv/D, and the ratio of pulse period to the period for peak spectral velocity （Tv-p） are utilized to quantify the difference between rock and soil sites for near-fault forward-directivity ground motions. The ATv/Vratio of recorded near-fault motions is substantially larger for rock sites than that for soil sites, while Tvp/Tv ratios are smaller at rock sites than at soil sites. Furthermore, using simple pulses and available predictive relationships for the pulse parameters, a preliminary model for the design acceleration response spectra for the near-fault region that includes the dependence on magnitude, rupture distance, and local site conditions are developed. 相似文献
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M. Navarro T. Enomoto F. J. Sánchez I. Matsuda T. Iwatate A. M. Posadas F. Luzón F. Vidal K. Seo 《Pure and Applied Geophysics》2001,158(12):2481-2497
—?In Almería city large earthquakes occurred and many buildings were completely destroyed in these historical earthquakes. The actual population of Almería city is about 200,000 people. This population is rapidly increasing and new urbanizing areas are growing to the eastern part of the city where they are located in softer soil conditions. Consequently, the evaluation of surface soil conditions is very important from a standpoint of earthquake disaster mitigation. We have obtained a landform classification map developed by analysing aerial photos, large-scale topographic maps and 80 borehole data. Eleven unit areas, which have different soil conditions, were inferred from this research. Also, S-wave velocity prospecting tests were carried out at several sites within the city. The shear-velocity values of the ground vary from 1689?m/s in hard rock to 298?m/s in soft soil. These results are useful for understanding the uppermost soil characteristics and are used for soil classification. Finally, short-period microtremor observations were densely carried out in the research area and NAKAMURA's method (1989) was applied for determining predominant periods. Microtremors were observed at about 173 sites with mainly 400?m interval in rock sites and 200?m interval in relatively soft soil sites. From the result of these microtremor measurements, the predominant period determined at rock site, in the western part of the city and historic area, is very short, about 0.1?s, and very stable. However at soft soil sites, in the center of the city, near Zapillo Beach and in the newly developed urban area, the predominant period is about 1.0?s and even larger in concordance with the geological conditions. Finally, at medium soil sites, in the eastern part of the city, the predominant period is about 0.4?s and it appears very stable in the whole region. The difference of predominant periods between hard rock and soft soil sites is very clear and it has been observed that the distribution of predominant periods depends heavily on the surface soil conditions. 相似文献
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四川省芦山县于2013年4月20日发生了7.0级地震，基于国家强震动台网中心发布的此次地震的2 106组余震强震动记录，利用基于NGA衰减关系的简化模型，使用随机效应方法拟合得到其PGA以及0.01~8 s周期下的伪加速度反应谱（阻尼比5%）的地震动衰减关系。与其他学者研究得出的四川其他地区衰减关系进行对比，本文模型能够较好地预测芦山余震强震动衰减。不论基岩场地和软土场地，本文在衰减关系在短周期均与卢大伟模型结果一致。但是在长周期情况下，本文模型在软土场地大于卢大伟结果，而在基岩场地上低于俞言祥结果。因此，在使用本文衰减关系时，要特别注意场地和周期对其的影响。 相似文献