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在研究西安地区大量钻孔资料的基础上,构造了44个不同等效剪切波速和覆盖层厚度场地条件下的典型场地剖面,利用一维等效线性化地震反应分析方法,计算了不同场地在3种不同强度的地震动输入下的地面峰值加速度,分析了地震动峰值加速度放大系数ks随场地类别、等效剪切波速Vse、覆盖层厚度H和输入地震动强度ar的变化特征,指出了按场地类别对地震动峰值加速度调整存在的问题。分析结果表明,加速度放大系数随等效剪切波速、覆盖层厚度及基岩输入地震动强度的增大而减小;等效剪切波速对加速度放大系数的影响大于覆盖层厚度的影响,随着输入地震动强度的增大,覆盖层厚度对加速度放大系数的影响成份有逐渐加大的趋势;覆盖层厚度对加速度放大系数的影响程度随着等效剪切波速的增大而逐渐减弱;加速度放大系数与场地等效剪切波速和覆盖层厚度之间具有较高的拟合度的统计回归关系。由此提出了直接用场地等效剪切波速和覆盖层厚度对地震动峰值加速度进行调整的新途径。最后,就地震动峰值加速度随场地条件的调整方法,提出了有待进一步研究的问题。 相似文献
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本文选取山东地区2个Ⅲ类场地的工程地质勘探及土层剪切波速等资料,将土层厚度按5个深度段,每个分段给出了4个土层剪切波速的改变量,通过改变不同深度段土层剪切波速,建立了19种土层地震反应分析模型,分析了不同深度段,不同概率水平下土层剪切波速的变化对场地地震动参数的影响。研究表明,不同深度段土层剪切波速的变化对场地地震动参数的影响有差异。具体表现为,土层剪切波速的改变在1—10m、11—40m和地震输入界面处三个深度段对地震动加速度峰值影响较大;其中,41—70m和71—100m两个深度段剪切波速的改变对地震动加速度峰值影响小;在土层深度1—10m时,剪切波速降低,峰值变大,剪切波速的改变与峰值的改变呈负相关;在其它深度段,剪切波速降低,峰值变小,剪切波速的改变与峰值的改变呈正相关。剪切波速的改变在1—10m和11—40m两个深度段对地震加速度反应谱影响较大;在41—70m、71—100m和地震输入界面三个深度段对地震加速度反应谱影响很小。 相似文献
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土层结构对地表加速度峰值的影响 总被引：20，自引：1，他引：20
本文在研究我国数百个工程场地钻孔资料的基础上，选取和构造了若干有代表性的典型场地剖面，利用目前工程上广泛应用的场地地震反应分析的一维等效线性化波动方法，计算了不同场地在三种不同强度的地震动输入下的地表加速度峰值反应。分析研究了覆盖层厚度、软土层的埋深与厚度等对场地地表加速度峰值的影响，得到了一些有意义的结论。 相似文献
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《华南地震》2017,(2)
基于深圳市前海自贸区填海场地某一典型的含软弱淤泥夹层钻孔剖面,对填海场地中软弱夹层的厚度和埋深对地面运动特性的影响进行分析。将原软弱夹层按2 m、4 m、6 m、8 m、10 m厚度,0 m(地表)、5 m、10 m、15 m、20 m、30 m、45 m(层底)埋深,构造出35个土层模型。利用土层一维等效线性化分析方法对上述35个土层模型进行不同超越概率地震动输入下的地震反应分析,结果表明:当输入地震动一定时,随着软弱夹层埋深的增加,地表加速度峰值放大倍数k逐渐减小,埋深超过一定深度后,k值小于1;随着软弱夹层的厚度增大,加速度峰值放大倍数k先增显大后减小;随着输入地震动的增大,各工况下地震地表加速度峰值放大倍数k相应都减小,地表加速度峰值减小明显。 相似文献
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剪切波速对场地地表地震动参数的影响 总被引：3，自引：2，他引：1
本文以江淮地区典型场地资料为原型,将土层剪切波速实测值按照一定比例进行增减,构造多种场地土层地震反应分析模型,选择Taft、E1centro和Kobe三条强震记录作为地震输入,采用一维频域等效线性化波动方法进行了土层地震反应分析.研究结果表明,剪切波速的变异性与场地地表地震动的影响程度与输入基岩地震动的频谱特性、幅值、土层结构等因素有关.地表峰值加速度随着剪切波速的增大而逐渐增大,地表加速度反应谱的特征周期随着剪切波速的增大而逐渐减小. 相似文献
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烟台海岸软土场地特征及对地震动参数的影响 总被引：1，自引：0，他引：1
本文利用剪切波速和钻孔资料，根据中国GB50011-2001规范、美国FEMA-NEHRP规范、欧洲EUROCODE 8规范，对烟台滨海软土场地类别进行评定。并通过场地地震动效应分析，研究滨海场地土特征对地震动的影响。结果表明，简单的场地类别划分难以反映软土场地的实际情况；滨海软土场地对地震动加速度的幅值和频谱的影响非常明显，其对峰值加速度的放大倍数较高，但受土的非线性变形影响，随地震动输入的增大其放大倍数呈非线性降低；软土场地使得加速度反应谱谱形变宽，特征周期变大。 相似文献
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An earthquake of magnitude ML=5.9 occurred in Dinar, a town located at the edge of an alluvial basin in Southeast Anatolia, Turkey. Inflicted structural damage throughout the town was highly concentrated in a region located on the alluvium and adjacent to the rock outcrop bounding the eastern side of the town. As an attempt to explain this discrepancy, possible effects of the edge of basin on which the town is located were investigated through 1D and 2D response analyses. Response spectra, computed at distinct locations of the town were contrasted to the building damage statistics of the three zones identified in the town. It is found that the 1D analyses considerably underpredict the spectral response in the heavily damaged area. Differences between the spectral responses obtained from the two approaches diminish with increasing distance from the rock outcrop. These results, which indicate that the 2D amplification was significant over a distance from the edge of the basin, provide a meaningful explanation for the observed distribution of damage throughout the town. 相似文献
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J.A. Morakinyo R. Mackay 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(1-2):106-118
The pattern of ground contamination across a site depends on the historical pattern of contaminant releases at the surface
and the redistribution and the fate of contaminants below the surface. Using these concepts a new site assessment approach
(assessment modelling) is proposed based on the development of three stochastic models: a model of the physical structure
of the ground materials beneath the site; a model of the distribution of surface contaminant spills; and a model of the flow
and transport of spilled material into the heterogeneous underlying ground to construct alternative, equally likely, present
day contaminant distributions. Combining the models within a Monte Carlo framework can, in principle, improve the understanding
of the potential for excess contamination across the site and improve decisions on remediation options and locations. A trial
application has been undertaken in the UK using a particular site to assess the approach. The conditions at the site used
for the trial and the first of the stochastic model developments, the geostatistical modelling of the soil heterogeneity,
are presented in this paper. Non-parametric and parametric geostatistics have been employed to formulate the geostatistical
models of the site soils using lithological information from 146 trial pits and boreholes. The approach to the soil modelling
and the verification and validation of the results are described. The heterogeneity of the subsurface is complicated by the
presence of made-ground, comprised of various inert building wastes, and the non-stationarity of the heterogeneity of the
natural ground. This paper is the first of three describing the assessment modelling methodology and its trial application
to the site. 相似文献
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The spectral ratio method is used here for evaluating the frequency dependence of a site amplification factor in the Messina Strait area. All stations exhibit the same features of spectral ratios evidencing two peaks at about 10 Hz and 16 Hz. We relate this observation to the same geological structures. In fact, all the stations (except the referenced one) are situated over pleistocenic sediments with a similar grain size. This causes the disappearing of any site effect when the average spectrum is used as a reference. MES station, situated in the city of Messina, presents a clear site effect at a different frequency (6 Hz) which cannot be related to any geological structure because no substantial difference is observed between the sediments on which this station is situated and the sediments on which the other stations are situated. MT1 station exhibits a spectral peak at about 2 Hz which can be explained with oscillations of a little sedimentary basin. 相似文献
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场地条件对地震动具有较大影响, 研究不同场地条件下的地震动特征对地震动的校正具有重要意义。 本文以九寨沟地震为例, 收集了66个台站的198条三分量强震观测记录和SRTM(Shuttle Radar Topography Mission)公里格网的DEM(Digital Elevation Model)数据, 从多个角度对场地特征进行分析。 首先根据坡度法使用DEM数据对九寨沟特征进行了场地分类, 然后讨论了不同场地类型下的加速度时程、 加速度反应谱、 地震动衰减等地震动特征。 研究表明, 缺少实测资料的情况下, 地形坡度可以作为Vs30(地表以下30 m范围的平均剪切波速度)的一种替代指标, 利用坡度法可以较快速地对场地进行分类; 利用强震观测记录能够从多角度对台站的场地特征进行分析, 不同场地类型对地震动影响不同, 其中, 土层对地震动具有明显的放大效应。 该结论可以为地震动结果的校正提供依据。 相似文献
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Earthquake-induced hazards are profoundly affected by site effects related to the amplification of ground motions, which are strongly influenced by local geologic conditions such as soil thickness or bedrock depth and soil stiffness. In this study, an integrated geographic information system (GIS)-based system for geotechnical data, called the geotechnical information system (GTIS), was developed to establish a regional counterplan against earthquake ground motions in the Seoul metropolitan area. In particular, to reliably predict spatial geotechnical information, a procedural methodology for building the GTIS within a GIS framework was developed and applied to the Seoul area in Korea. To build the GTIS, pre-existing geotechnical data were collected in and around the study area, and then a walk-over site survey was conducted to acquire surface geo-knowledge data. In addition, the representative shear wave velocities for geotechnical layers were derived by statistically analyzing many seismic test data in Korea. The GTIS was used in a practical application to estimate site effects in the study area; seismic zoning maps of geotechnical earthquake parameters, such as the depth to bedrock and the site period, were created and presented as a regional synthetic strategy for earthquake risk assessment. Furthermore, seismic zonation of site classification was also performed to determine the site amplification coefficients for seismic design and seismic performance evaluation at any site and administrative sub-unit in the study area. The methodology and results of the case study of seismic zonations in the Seoul area verified that the GIS-based GTIS can be very useful for the regional estimation of seismic risk and also to support decisions regarding seismic hazard mitigation, particularly in the metropolitan area. 相似文献
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Our previous studies show that site effects (amplification of rock motions), source and path effects are coupled when response spectra are used to characterize the amplification ratios for a soil site modelled as nonlinear or elastic. The coupling is referred to as a “side effect” of using response spectral amplification ratios. In the present study we use a suite of rock site records, well distributed with respect to magnitude and source distance, from crustal, subduction interface and slab earthquakes to evaluate the response spectral amplification ratio for soft soil sites. We compare these side-effects for ground motions generated by three types of earthquakes, and we find that, at periods much shorter or much longer than the natural period of a soil site modelled as elastic, the average amplification ratios with respect to rock site ground motions from three types of earthquakes are moderately different and are very similar for other spectral periods. These differences are not statistically significant because of the moderately large scatter of the amplification ratios. However, the extent of magnitude- and source-distance-dependence of amplification ratios differs significantly. After the effects of magnitude and source distance on the amplification ratios are accounted for, the differences in amplification ratios between crustal and subduction earthquake records are very large in some particular combinations of source distance and magnitude range. These findings may have potential impact in establishing design spectra for soft soil sites using strong motion attenuation models or numerical modelling. 相似文献
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我国现行抗震设计规范中场地评定方法的比较和评述 总被引：1，自引：0，他引：1
目前，我国抗震设计规范中采用的场地评定方法主要有两种：一是建筑抗震设计规范（ＧＢＪ１１－８９）采用的场地分类的方法，一是构筑物抗震设计规范（ＧＢ５０１９１－９３）和电力设施抗震设计规范采用的场地指数法。前者是把场地影响按照场地分类指标划分成若干场地类别，因此，确定的地震荷载是不连续的，跳跃变化的。后者是一种以模糊推论的综合评判方法导出的场地指数为指标进行连续评定的新方法，在这种方法里，场地性质的差 相似文献
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盘锦、海城、营口地区是辽宁省内地震活动性最强、地震危险性最高的地区。该地区开展了大量重点工程地震安全性评价、区域性地震区划和地震小区划工作，但尚未开展基于场地条件的区域尺度地震危险性研究。独有的沉积特点使该地区场地条件较复杂，因此在地震危险性概率分析中考虑场地条件是必要的。本文基于新一代中国地震动参数区划图基本原理和技术原则，结合盘锦、海城、营口地区场地条件特征，采用基于地形坡度的方法对场地条件进行分类，确定场地地震动影响系数，给出该地区基于区域场地条件的地震危险性分布，相关研究结果可为地震风险评估和防震减灾规划提供参考。 相似文献
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Site characterizations for the Iranian strong motion network 总被引：2，自引：0，他引：2
Twenty-six sites of the Iranian strong motion network, having provided numerous records of good quality, were selected for a site effect study with the objective of obtaining a reliable site categorization for later statistical work on Iranian strong motion data. For each site, superficial Vp and Vs profiles were measured with refraction techniques, microtremor recordings were obtained and analysed with the H/V technique and the available three-component accelerograms by the receiver function technique. The aggregation of these results allows the proposition of a four-class categorization based on the H/V spectral ratio of strong ground motions, which demonstrate a satisfactory correlation with the S-wave velocity profile. Iran has a particular geological and meteorological situation compared to other seismic countries such as Japan or California, a mountainous country with dry weather conditions and a low water table in most areas. These conditions result in a relatively small number of sites with low frequency amplification, while many sites exhibit moderate amplifications in the intermediate and high frequency range. 相似文献
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This study proposes a recording-based approach to characterize and quantify earthquake-induced site nonlinearity, exemplified as soil nonlinearity and/or liquefaction. Alternative to Fourier spectral analysis (FSA), the paper introduces time–frequency analysis of earthquake ground motion recordings with the aid of so-called Hilbert-Huang transform (HHT), and offers justification for the HHT in addressing the nonlinear features shown in the recordings. With the use of the 2001 Nisqually earthquake recordings, this study shows that the proposed approach is effective in characterizing site nonlinearity and quantifying the influences in seismic ground responses. Major results from this study are listed below.
- 1. HHT-based site amplification is defined as the ratio of marginal Hilbert amplitude spectra, similar to the Fourier-based one that is the ratio of Fourier amplitude spectra. The HHT-based site amplification can be used in effectively quantifying site nonlinearity in terms of frequency downshift in the low-frequency range and amplification-reduction factor in intermediate-frequency range in comparison with the Fourier-based one.
- 2. Instantaneous damping, and Hilbert and marginal Hilbert damping spectra are defined in ways similar to instantaneous frequency, and Hilbert and marginal Hilbert amplitude spectra, respectively. Consequently, the HHT-based site damping is found as the difference of marginal Hilbert damping spectra, which can be used as an alternative, complementary index to measure the influences of site nonlinearity in seismic ground responses.
Keywords: Site nonlinearity; Site amplification; Site damping; Hilbert-Huang transform (HHT); Liquefaction; 2001 Nisqually earthquake 相似文献