共查询到19条相似文献，搜索用时 140 毫秒
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《地震工程与工程振动》2016,(5)
对以往曾经发生显著液化的唐山地区和巴楚地区的土动力学性能进行对比研究,包括两个地区砂土相对密度与剪切波速关系、剪切波速与标准贯入击数关系等,以此深入了解两个重要地区土层的动力性能,为研究区域化液化判别方法提供基础。结果表明:现行抗震规范液化判别方法数据来源主要为唐山地区,明显不适用于新疆巴楚地区的液化判别;唐山地区与巴楚地区液化场地砂土取相同相对密度时,两个地区液化场地砂土剪切波速差别很小;但唐山地区与巴楚地区液化层砂土平均标准贯入击数和V_s~N_(63.5)关系曲线差异显著,表明以V_s~N_(63.5)关系区分不同地区砂土抗液化能力是可能的。 相似文献
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以剪切波速为宗量的一种砂土地震液化的不确定性判别法 总被引：6，自引：0，他引：6
利用基于剪切波速的砂土液化判别法，本文提出了一种可考虑剪切波速的随机性和液化及液化危害等级的模糊性的液化和液化危害等级的判别法。作者首先讨论了当剪切波速具有随机性时液化的发生概率，进而给出了确定场地液化和危害程度的发生概率。在此基础上，结合液化和液化危害程度（等级）的模糊性，利用模糊事件的概率分析方法，提出了可同时考虑随机性和模糊性的场地液化和液化危害性的发生概率的计算方法。 相似文献
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《世界地震工程》2016,(1)
通过搜集国内外现有的地震液化实测数据,利用皮氏积距相关系数法分析了影响砂土液化的PGA、地下水位、饱和砂层埋深、标贯击数以及剪切波速等特征参数与液化的相关性,对比研究了在不同埋深、地下水位和烈度范围内各参数相关性的表现以及各参数相关性间的对比,得到了实际动荷情况、真实埋藏条件以及现场实测下土力学指标与液化关联性的真实结果。分析结果表明:地下水位、砂层埋深、标贯击数和剪切波速与液化呈负相关,PGA与液化呈正相关;砂层埋深、标贯击数与液化显著相关,而地下水位和剪切波速与液化相关性不显著;标贯击数与液化的相关性最大,其次为埋深、PGA和水位,最小为剪切波速。 相似文献
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含细粒土体相对于纯净砂在自然界中分布更为广泛,其地震液化灾害在上世纪70年代之后逐渐成为研究热点,然而关于其液化判别,一直以来都只是在砂土方法的基础上,稍作调整。本文对比了美国NCEER推荐的基于标贯试验的Seed方法和基于剪切波速试验的Andrus和Stokoe方法,以历史地震数据检验方法,结果显示剪切波速方法对含细粒土体过于保守,并且细粒含量越高,对非液化点越不可靠。通过建立两个方法 3组细粒含量下液化临界曲线上的剪切波速与标贯击数相关关系,得出临界剪切波速随细粒含量增加而减小的趋势没有临界标贯击数那么迅速。剪切波速试验为小应变无损测试,对含细粒土土颗粒间胶结力较为敏感,而液化状态为大应变破坏阶段,土体胶结力基本丧失,因此对胶结较强的含细粒土体,剪切波速指标与液化难以建立唯一联系。另外,中国规范剪切波速液化判别方法存在误导,由于判别式已经用黏粒含量修正,因此,V_(s0)经验系数应统一只取砂土数值。 相似文献
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剪切波速是评估无黏性土力学性质的重要参数。为探究现行剪切波速液化判别方法不适用于砾性土场地的原因,利用自主研发的无黏性土剪切波速与相对密度联合测试系统,以汶川地震液化场地实测资料为参考,通过对福建标准砂和花岗岩圆砾按比例混合配制不同含砾量的砾性土试样在控制相对密度下的K0状态剪切波速试验,研究其含砾量对含砾无黏性土的剪切波速影响规律。试验结果表明:相对密度相同的砾性土剪切波速大于砂土,二者剪切波速比值与砾性土的含砾量成指数函数关系,两者比值最大为1.4;对于砾性土试样,在含砾量40%-60%间存在阀值,当含砾量小于该值,剪切波速随含砾量的增加明显增大,当含砾量大于该值,剪切波速的增长趋势放缓。试验研究指出了现行剪切波速判别方法不适用于砾性土场地的原因,揭示了含砾量与砾性土剪切波速的相互关系,提出了相同相对密度砾性土相对砂土的剪切波速修正公式,为建立新的判别方法提供了理论基础,也为岛礁珊瑚吹填土等宽级配无黏性新工程材料的性能研究拓展了技术手段。 相似文献
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《国际地震动态》2017,(5)
黄土液化的判别是工程界长期存疑的问题,现场黄土含水量较低,剪切波速较高,而实验室对其饱和,饱和过程对其土体结构影响还不确定,又由于固结比对土体刚度的影响仍然没有定论,这就导致室内黄土动三轴液化试验结果与现场力学指标一直无法建立联系。另一方面,黄土从颗粒组成来说,属于细粒土范畴,细粒土液化判别方法应可为黄土液化判别提供参照,但由于实验室配制试样相对密度、土体骨架强度及细颗粒赋存形式很难控制,导致细颗粒对土体液化势影响研究饱含争议与矛盾。本文紧密结合工程和科研工作需求,设计了一系列原状黄土在均等固结与偏压固结下的动三轴弯曲元试验,以及原状黄土在动三轴内饱和过程及饱和后的剪切波速试验,并且对一个饱和黄土场地进行了现场原位测试,回顾了现有标贯液化判别方法,对含细粒土体液化判别指标进行了系统研究,改进了细粒土液化初判准则以及含细粒砂性土液化判别式,最后对CPT液化判别方法的可靠性进行了数据检验。具体工作和成果包括:(1)采用动三轴弯曲元试验系统,对兰州市多个场地原状黄土进行了均等固结与偏压固结下剪切波速测试,证实了相关固结比对土体刚度影响的试验研究结果,进一步对比均等固结与偏压固结下试样轴向变形,分析了固结比对土体刚度影响的机理。(2)采用动三轴弯曲元试验系统,首先对原状黄土饱和过程进行了剪切波速跟踪测试,并进一步对比饱和黄土与原状黄土在同一逐级加压的过程中剪切波速与轴向变形测试值,最后通过与现场饱和黄土场地水位上下黄土层实测标贯击数、剪切波速对比,分析了原状黄土遇水及饱和后的软化特征。(3)通过对比唐山、海城地震两个液化地区粉土与砂土的剪切波速与标贯击数统计关系,发现对于剪切波速相同的饱和粉土和砂土,由于粉土的触变性,粉土标贯击数显著小于砂土。结合NCEER推荐的基于SPT与VS的液化判别方法,建立了3个细粒含量下临界剪切波速与临界标贯击数的相关关系,证实了含细粒土体的触变性。(4)回顾了目前国内外有关含细粒土液化研究现状,结合1975年海城地震,1976年唐山地震,1999年土耳其Kocaeli地震和台湾集集地震液化与非液化土数据分析,详细对比了现有液化判别式和初判条件的优劣,改进了细粒土液化初判准则以及含细粒砂性土标贯液化判别式。(5)回顾了NCEER推荐的Robertson的CPT液化判别方法和Olsen的CPT液化判别方法,通过对1999年台湾集集地震液化与非液化土数据分析,并将判别结果与SPT方法判别结果进行比较,指出了CPT液化判别方法还没有达到SPT方法的准确性,但是CPT的土分类图却是其最大的优势所在。 相似文献
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Chih-Ping Lin Cheng-Chou Chang Tzong-Sheng Chang 《Soil Dynamics and Earthquake Engineering》2004,24(9-10):689
The multi-channel analysis of surface wave (MASW) method is a non-invasive method recently developed to estimate shear wave velocity profile from surface wave energy. Unlike conventional SASW method, multi-station recording permits a single survey of a broad depth range and high levels of redundancy with a single field configuration. An efficient and unified wavefield transform technique is introduced for dispersion analysis and on site data quality control. The technique was demonstrated in the assessment of soil liquefaction potential at a site in Yuan Lin, Taiwan. The shear wave velocity and liquefaction potential assessments based on MASW method compares favorable to that based on SCPT shear wave measurements. Two-dimensional shear wave velocity profiles were estimated by occupying successive geophone spreads at several sites in central western Taiwan, at some of which sand boils or ground cracks occurred during 1999 Chi Chi earthquake. Liquefaction potential analysis based on MASW imaging was shown to be effective for estimating the extent of potential liquefaction hazard. 相似文献
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A series of undrained cyclic direct simple shear tests, which used a soil container with a membrane reinforced with stack rings to maintain the K0 condition and integrated bender elements for shear wave velocity measurement, were performed to study the liquefaction characteristics of gap-graded gravelly soils with no fines content. The intergrain state concept was employed to categorize gap-graded sand–gravel mixtures as sand-like, gravel-like, and in-transition soils, which show different liquefaction characteristics. The testing results reveal that a linear relationship exists between the shear wave velocity and the minor fraction content for sand–gravel mixtures at a given skeleton void ratio of the major fraction particles. For gap-graded gravelly sand, the gravel content has a small effect on the liquefaction resistance, and the cyclic resistance ratio (CRR) of gap-graded gravelly sands can be evaluated using current techniques for sands with gravel content corrections. In addition, the results indicate that the current shear wave velocity (Vs) based correlation underestimates the liquefaction resistance for Vs values less than 160 m/s, and different correlations should be proposed for sand-like and gravel-like gravelly soils. Preliminary modifications to the correlations used in current evaluations of liquefaction resistance have thus been proposed. 相似文献
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地基抗液化能力评估方法讨论 总被引：1，自引：1，他引：0
为了评估地基抵抗液化的能力及其影响因素,本文介绍了标准贯入试验、静力触探试验以及剪切波速试验三种评估地基抗液化能力方法的研究成果,分析了震级比例系数、覆盖压力与倾斜地面的修正系数、地震震级与峰值加速度的影响,并对地基抗液化能力的概率分析方法进行了讨论,得到的结论可为地基的抗液化能力评估提供参考。 相似文献
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Evolution of the shear wave velocity during shaking modeled in centrifuge shaking table tests 总被引：2，自引：1，他引：1
Chung-Jung Lee Chung-Ru Wang Yui-Chen Wei Wen-Yi Hung 《Bulletin of Earthquake Engineering》2012,10(2):401-420
Two in-flight shear wave velocity measurement systems were developed to perform the subsurface exploration of shear wave velocity
in a centrifuge model. The bender elements test and the pre-shaking test used in the study provided reliable and consistent
shear wave velocity profiles along the model depth before and after shaking in the centrifuge shaking table tests. In addition,
the use of the bender elements measurement system particularly developed here allowed continuous examination of the evolution
of shear wave velocity not only during and after the shaking periods in the small shaking events but also during the dissipation
period of excess pore water pressure after liquefaction in the large shaking events. The test results showed that the shear
wave velocity at different values of excess pore water pressure ratio varied as the effective mean stress to the power of
0.27, to a first approximation. Consequently, a relationship between the shear wave velocity evolution ratio and the excess
pore water pressure ratio is proposed to evaluate the changes in shear wave velocity due to excess pore water generation and
dissipation during shaking events. This relation will assist engineers in determining the shear stiffness reduction ratio
at various ru levels when a sand deposit is subjected to different levels of earthquake shaking. 相似文献
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Shear wave velocity-based liquefaction evaluation in the great Wenchuan earthquake： a preliminary case study 总被引：2，自引：1，他引：1
The great Wenchuan earthquake (Ms = 8.0) in 2008 caused severe damage in the western part of the Chengdu Plain. Soil liquefaction was one of the major causes of damage in the plain areas, and proper evaluation of liquefaction potential is important in the definition of the seismic hazard facing a given region and post-earthquake reconstruction. In this paper, a simplified procedure is proposed for liquefaction assessment of sandy deposits using shear wave velocity (Vs), and soil liquefaction from the Banqiao School site was preliminarily investigated after the earthquake. Boreholes were made at the site and shear wave velocities were measured both by SASW and down-hole methods. Based on the in-situ soil information and Vs profiles, the liquefaction potential of this site was evaluated. The results are reasonably consistent with the actual field behavior observed after the earthquake, indicating that the proposed procedure is effective. The possible effects of gravel and fines contents on liquefaction of sandy soils were also briefly discussed. 相似文献
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This study analyzes liquefaction in the Kumluca/Antalya residential area and surroundings, using seismic velocities of soil deposits and the predominant period of the earthquake wave. The liquefaction analysis calculates shear–stress ratio, shear–resistance ratio and safety factor. Shear wave velocity used in liquefaction analysis was determined through surface waves. Moreover, the dynamic parameters of the ground were calculated through seismic velocities. Distributions of groundwater, shear wave velocity, adjusted shear wave velocity, predominant period of vibration, soil amplification and ground acceleration of the research area were mapped. In addition, the liquefied and non-liquefied areas as a result of liquefaction analysis in Kumluca were determined and presented as maps. Examining these maps, among all these maps, the limits of the lagoon sandbar and the old lake area were determined using only the liquefaction map. 相似文献
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Estimation of residual shear strength ratios of liquefied soil deposits from shear wave velocity 总被引：1，自引：1，他引：0
Pelinzener 《地震工程与工程振动(英文版)》2012,11(4):461-484
For sites susceptible to liquefaction induced lateral spreading during a probable earthquake, geotechnical engineers often need to know the undrained residual shear strength of the liquefied soil deposit to estimate lateral spreading displacements, and the forces acting on the piles from the liquefied soils in order to perform post liquefaction stability analyses. The most commonly used methods to estimate the undrained residual shear strength (Sur) of liquefied sand deposits are based on the correlations determined from liquefaction induced flow failures with SPT and CPT data. In this study, 44 lateral spread case histories are analyzed and a new relationship based on only lateral spread case histories is recommended, which estimates the residual shear strength ratio of the liquefiable soil layer from normalized shear wave velocity. The new proposed method is also utilized to estimate the residual lateral displacement of an example bridge problem in an area susceptible to lateral spreading in order to provide insight into how the proposed relationship can be used in geotechnical engineering practice. 相似文献