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1976年唐山地震期间,附近一些地区出现了砂土液化现象。本文根据工程勘探中的实例及实验数据,进行了砂土液化作用的统计和综合预测。文章中采用贝叶斯准则下的逐步判别分析方法,对唐山地区已知液化地点和非液化地点,作了五种检验计算,挑选出准确度及可靠性最高的变量模式。从而,对于当地震为Ⅷ度烈度时的砂土液化进行了预测。五种预测结果相同,互相印证,可靠性高,分组最大后验概率大多在0.99以上。在此条件下,外推预测结果可信。工程实践中,迫切需要对砂土液化进行综合性预测,而一般采用地质学或试验方法,仅能对砂土液化作单因素或少量因素下的预测,本文提出了综合性的通用预测方法,为砂土液化统计预测提供了新途径。砂土液化是平原地区的一种重要地震灾害。国内外多次大地震中,都曾因饱水砂土受到地震作用,引起孔隙水压增高及砂粒间的结合力和摩擦力降低,而使砂层发生液化状态的流动,并伴随有地基承载能力降低或失效。1964年以来,新潟地震及阿拉斯加地震时,由砂土液化造成了罕见的灾害。激发了各国、尤其是美国和日本对砂土液化预测的研究。但还多是单因素或少量因素影响下的分析方法。未能进行综合分析及推断。采用数理统计方法,可以综合分 相似文献
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砂土液化是一种重要震害现象。近年来,关于影响砂土液化各因素的研究愈发引人注目。但常用的实验及地质学方法,仅限于研究单一或少量因素与液化间的关系。而缺乏对形成砂土液化的多种条件的综合性分析。笔者采用数理统计的方法,对唐山地震时,影响砂土液化发生的十五个因素进行了综合性分析。初步认识了它们的相对重要性 相似文献
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饱和砂土液化研究进展 总被引:7,自引:1,他引:6
根据国内外文献资料,从三方面总结了饱和砂土的最新进展:饱和砂土液化判别方法、砂土液化的试验研究以及液化后分析,特别是探讨了液化对上部结构的影响。最后指出了存在的问题和今后的研究方向。 相似文献
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基于地震模拟振动台试验,配制3组不同平均粒径和3组不同细粒含量的6个砂土模型,通过埋置于砂土内部的传感器监测模型内部不同位置的超孔隙水压力等指标,分析砂土模型内部的超孔隙水压力时程曲线及孔压比时程曲线,归纳出地震波加载峰值、砂土平均粒径、细粒含量及埋置深度等因素对饱和砂土液化特性的影响规律。试验结果表明:随着地震波加载峰值的增大,砂土模型液化程度逐渐增大,液化势逐渐增大,抗液化强度逐渐减小;随着砂土埋置深度的增加,砂土细粒含量的增加,砂土平均粒径的增加,砂土模型液化程度逐渐减小,液化势逐渐减小,其抗液化强度逐渐增大。同时,试验结果还表明,砂土液化各影响因素对砂土液化的影响程度依次为地震波强度>砂土埋置深度>砂土平均粒径、细粒含量。试验结果可为后续数值模拟的参数选取提供支持,为研究其他因素对砂土液化的影响提供参考。 相似文献
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本文总结了Rayleigh波场数值模拟的4种思路和各自特点,根据Lamb问题的理论分析成果提出了基于地表激振的Rayleigh波场数值模拟技术,论述了地表集中震源作用下引起地表波动场的特点及主要影响因素。在此基础上,利用Plaxis 2D有限元软件实现了Rayleigh波场的数值模拟,并结合算例验证了所提方法的可行性和结果的合理性。最后,针对多层建筑结构,研究了不同地震动输入模式下结构动力反应的特点。结果表明,Rayleigh波作用下结构的动力反应特性明显区别于在底部输入剪切波时的结果,不同地震动输入模式对结构的振动形态和破坏模式有着明显的影响。 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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The modeling methodologies and calculation of dynamic response of underground structure under Rayleigh waves is investigated in this paper. First the free field responses under Rayleigh waves are analyzed and the numerical results agree well with the theoretical results. Then, the approximate Rayleigh waves are put forward based on the preliminary re-search, and Rayleigh wave field is obtained through fast Fourier transform technique. Taking a utility tunnel as an example, its dynamic responses under Rayleigh waves is calculated by ABAQUS. The results demonstrate that bending deformation is the main component of structural deformation and the deformation at the top of the structure is about twice as much as that at bottom of the structure. The effect of soil-structure interface and the buried depth of underground structure are also investi-gated via parameter analysis. For the shallow buried underground structures, Rayleigh waves can be the key factor to control the responses and damage of the structure. 相似文献
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应用剪切波速判别砂土液化的研究综述 总被引:5,自引:0,他引:5
首先介绍了应用剪切波速判别饱和砂土振动液化的原理;然后从临界剪应变取值、砂土的抗液化能力与剪切波速相关关系的研究方法与设备、用剪切波速进行扰动评价、建立适用于不同土类的统一判别式四方面总结了国内外学者在该领域的一些研究成果及存在问题;最后针对以上问题提出作者的一些看法。 相似文献
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Jie Li Qingxia Yue Jun Chen State Key Laboratory for Disaster Reduction in Civil Engineering Tongji University Shanghai China School of Civil Engineering Sh ong Jianzhu University Ji’nan China 《地震学报(英文版)》2010,(1):13-24
The modeling methodologies and calculation of dynamic response of underground structure under Rayleigh waves is investigated in this paper. First the free field responses under Rayleigh waves are analyzed and the numerical results agree well with the theoretical results. Then, the approximate Rayleigh waves are put forward based on the preliminary re-search, and Rayleigh wave field is obtained through fast Fourier transform technique. Taking a utility tunnel as an example, its dynamic responses under Raylei... 相似文献
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High resolution seismic reflection exploration for minerals places severe demands on field practice so as to maximize the signal-to-noise bandwidth. In particular, all horizontally propagating coherent noise, especially ground roll, must be attenuated. The blocking effect of a trench between source and receiver has been investigated by means of two-dimensional physical seismic model experiments. Rectangular, circular and wedge-shaped saw-cuts of various dimensions were studied. The results show that thin rectangular cuts of depth equal to one-quarter of the Rayleigh wave noise wavelength produce a 12 dB or better improvement in the signal-to-noise ratio. Rayleigh wave attenuation is greater than 30 dB at a cut depth of one wavelength. In the field applications envisaged, this corresponds to trenches up to a few metres deep. The trenches should be filled with foam or loose sand to dampen out mode conversion and diffraction noise. There are obvious practical difficulties of implementing such a technique in routine CMP operations. The technical effectiveness of the saw-cut is illustrated by imaging a deeply-buried small hole (diffractor) in an aluminium plate. Without the saw-cut between source and receiver, the seismic record is dominated by Rayleigh wave noise, masking P-wave arrivals from the target diffractor. However, with a saw-cut of depth three-quarters of a Rayleigh wave wavelength, the improvement is dramatic, making it easy to detect and identify the hole. When scaled to the field situation, this is equivalent to imaging a 6 m tunnel at a depth of 400 m, using a surface trench of depth 2 m to block ground roll. 相似文献
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A laboratory study on the undrained strength of a silty sand from Central Western Taiwan 总被引:2,自引:0,他引:2
Yao-Tao Huang An-Bin Huang Yu-Chen Kuo Ming-Dou Tsai 《Soil Dynamics and Earthquake Engineering》2004,24(9-10):733
The sand deposit in Central Western Taiwan typically contained significant amounts of fines. The assessment of liquefaction potential using the simplified procedure often involved adjustment in field test results to account for the effects of fines. The available fines content (FC) adjustment methods are highly empirical and may lead to very different conclusions. The need and/or level of FC adjustment should be justified based on cyclic behavior of sand and its relationship with fines. This study made an attempt to provide that reference information for a silty sand commonly found in Central Western Taiwan. A series of isotropic consolidation, undrained monotonic and cyclic triaxial tests were conducted on reconstituted Mai Liao Sand (MLS) with various FCs and densities. Concurrent shear wave velocities were measured using bender elements in some of the cyclic triaxial tests. This paper describes the geological background, the laboratory tests and their implications in the assessment of liquefaction potential for MLS. 相似文献
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本文在考虑碎石桩排水和应力集中作用的基础上分析了碎石桩处理液化地基后复合地基的抗液化能力,并与自由场液化地基的抗液化能力进行了对比,提出了一种适用于碎石桩复合地基修正“Seed简化法”,可应用标准贯入试验对液化地基的处理效果进行评价。 相似文献
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Liquefaction macrophenomena in the great Wenchuan earthquake 总被引:3,自引:2,他引:1
Longwei Chen Xiaoming Yuan Zhenzhong Cao Longqing Hou Rui Sun Lin Dong Weiming Wang Fanchao Meng Hongjuan Chen 《地震工程与工程振动(英文版)》2009,8(2):219-229
On May 12, 2008 at 14:28, a catastrophic magnitude M 8.0 earthquake struck the Sichuan Province of China.The epicenter was located at Wenchuan (31.00°N, 103.40°E). Liquefaction macrophenomena and corresponding destruction was observed throughout a vast area of 500 km long and 200 km wide following the earthquake. This paper illustrates the geographic distribution of the liquefaction and the relationship between liquefaction behavior and seismic intensity, and summarizes the liquefaction macrophenomena, including sandboils and waterspouts, ground subsidence, ground fissures etc., and relevant liquefaction features. A brief summary of the structural damage caused by liquefaction is presented and discussed. Based on comparisons with liquefaction phenomena observed in the 1976 Tangshan and 1975 Haicheng earthquakes, preliminary analyses were performed, which revealed some new features of liquefaction behavior and associated issues arising from this event. The site investigation indicated that the spatial non-uniformity of liquefaction distribution was obvious and most of the liquefied sites were located in regions of seismic intensity Ⅷ. However, liquefaction phenomena at ten different sites in regions of seismic intensity Ⅵ were also observed for the first time in China mainland. Sandboils and waterspouts ranged from centimeters to tens of meters, with most between 1 m to 3 m. Dramatically high water/sand ejections,e.g., more than 10 m, were observed at four different sites. The sand ejections included silty sand, fine sand, medium sand,course sand and gravel, but the ejected sand amount was less than that in the 1976 Tangshan earthquake. Possible liquefaction of natural gravel soils was observed for the first time in China mainland. 相似文献