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1.
视电阻率及其差分曲线在岩土分层中的应用 总被引：2，自引：1，他引：1
将视电阻率曲线与视电阻率一阶差分曲线应用于岩土工程施工中．对两种曲线比较后发现,两种曲线均为有效的视电阻率信息．视电阻率一阶差分曲线具有较视电阻率曲线更高的分辨率．两种方法结合使用能较好地对岩土进行分层．当视电阻率存在明显差异且岩层厚度较大时,可用视电阻率曲线对岩土进行分层;当视电阻率差异较小时,则用视电阻率一阶差分曲线对岩土进行分层． 相似文献
2.
微动探测方法是在背景噪声成像理论的基础上发展起来的一种新型地球物理探测手段,其根据获取野外数据的观测台站方式分为微动阵列方法和微动单台方法.本文综述了前人对微动探测方法的研究进展,并对目前该方法存在的问题及研究的发展趋势进行了展望.微动阵列方法采用频率波数法或空间自相关法从微动信号中提取频散曲线,进而反演获得地下横波速度结构.微动单台方法即H/V谱比法以三分量台站为观测基础,对水平分量信号与垂直分量信号进行傅里叶谱比,以此估算沉积层厚度、获得共振频率以及场地放大因子等.目前微动探测发展还有诸多问题需要进行深入研究,例如瑞雷波与勒夫波浅层探测理论方法、同时考虑基阶和高阶面波的影响进行多阶面波反演方法研究以及H/V谱比曲线与频散曲线联合反演方法研究等,从而提高微动探测方法浅层探测精度以满足城市地下空间精细探测的需求,加深探测深度为透明地壳、地下第三空间的精细探测提供一种新型地球物理手段. 相似文献
3.
"孤石"是花岗岩不均匀风化所残留的风化核,在我国南方沿海地区普遍发育."孤石"埋藏分布随机,形状大小各异,给地铁盾构施工带来重大安全隐患,探测"孤石"一直是地铁工程勘察面临的难题.我们首次尝试利用二维微动剖面技术探测"孤石",在深圳地铁7号线车公庙-上沙段区间实测二条剖面,结合少量钻孔资料进行岩性层划分和"孤石"解释.实测结果显示,在二维微动视S波速度剖面上,素填土、粉质粘土、砾质粘性土等岩土层、全风化、强-中风化、微风化和未风化的花岗岩层,视S波速度值各不相同,剖面特征也存在较大差异,利用少量钻孔结果标定,易于划分;在强-中风化花岗岩层中,视S波速度(岩性)横向变化剧烈,局部发育"团块状"高速体,本文将其解释为未风化的花岗岩"孤石".本文结果表明,二维微动剖面技术探测"孤石"是有效的微动视S波速度剖面除能直观显示岩性的纵、横向变化,提供工程基岩面的埋深及起伏形态信息外,还可给出岩土层风化程度的判断信息,为高层建筑的桩基设计提供地球物理依据.作为一种全新的"孤石"探测手段,二维微动剖面技术尤其适用于交通繁忙、建筑物密集的、各种场源干扰严重的闹市区. 相似文献
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为充分利用微动信号中基阶和高阶模式瑞雷波,本文研究了基于多阶瑞雷波SPAC系数直接反演的方法.该方法首先基于地层介质响应计算多阶瑞雷波的能量占比,考虑实际观测台阵有限台站个数对SPAC系数影响,正演计算多阶瑞雷波SPAC系数,再采用快速模拟退火算法对其反演以获得地下介质横波速度结构.在此基础上,本文通过数值模拟验证该方法的可靠性,分别选取三种典型地质模型,基于模式叠加算法合成理论微动信号,采用本文方法计算其理论多阶瑞雷波SPAC系数并反演,给出反演结果与真实模型对比.我们将该方法应用于上海中心城区的地质调查中,通过与钻探结果对比,进一步验证该方法的有效性.本文理论与实际应用研究表明,基于多阶瑞雷波SPAC系数直接反演的微动探测方法有助于提高反演结果的可靠性,尤其对含软硬夹层的复杂地层介质,可提高探测精度. 相似文献
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微动探测是利用地球表面的天然震动信号进行探测的被动源探测方法.相对于传统的物探方法,微动探测野外施工灵活,阵列形状多样,受施工场地限制小,对施工环境影响小.目前进行微动探测所用的地震检波器大多成本较高、重量和体积大,不便于运输与大规模布设.本文由微动探测方法的特点出发,优化改造了自行研发的低成本自存储式数字地震检波器,使其性能满足微动探测的需要.通过对地震计系统噪声的详细分析、微动探测原理的讨论,结合现场试验数据,探讨了该检波器应用于大规模微动探测的可行性. 相似文献
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微动台阵探测技术及其应用研究 总被引：10，自引：0，他引：10
介绍了利用微动台阵技术探测地壳浅层横波速度结构的仪器设备、观测系统、野外采集和数据处理方法，给出了用空间自相关方法测定相速度和浅层速度结构反演的实例。由于该方法不需要专门的震源，对于探测从地表到3km深度范围的地层结构具有经济、快捷、应用范围广泛等优点，因此将成为一种新的具有很好应用前景的地球物理勘探方法。 相似文献
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瓦斯突出是当前影响我国煤矿安全生产的主要因素之一.由于不同性质的煤层其瓦斯突出的可能性不同,原生煤具有低瓦斯炙出可能性,构造煤瓦斯突出可能性较大,而具有软分层特征的构造煤其瓦斯突出的可能性极高.由于不同性质煤层间的岩性差异较大,构造煤的泊松比要比原生煤的泊松比大0.1～0.2.因此,不同煤层与其顶、底板岩性差异不同,从而其顶、底板反射波的AVO曲线存在较大差异.从而可以通过AVO分析技术探测瓦斯突出可能性较高的构造煤的分布,特别是具有软分层特征构的造煤的分布.通过这种方式可以为煤矿安全生产提供第一手的地质资料.但目前AVO技术是以石油工业为基础发展而来的,并不完全适用于煤系地层.通过对煤层顶、底板AVO曲线的对比分析,发现目前常用的AVO近似方程对煤系地层来说精度较低,严重影响AVO分析精度.本文通过对Zoeppritz方程及其主要近似方程的分析对比,提出了一种改进的Hilterman近似方程,从而极大地提高了煤系地层AVO曲线的近似精度,使高精度的煤系地层AVO分析成为可能.另外,通过对构造煤顶、底板AV0曲线的分析,发现构造煤底板反射波较复杂并不适合AVO分析,而其顶板反射波规律性较强有利于AVO分析. 相似文献
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复杂山区的公路建设运营对地球物理探测提出了巨大挑战.非侵入式微动探测方法无需主动震源,作为地震类方法的一种,其独特的优势已经体现在地热资源探测、城市地下空间精细探测等领域.针对目前山区公路建设运营中对地球物理探测的重大需求,本文研究微动探测方法的应用效果.首先,根据研究区地形设计了十字形与直线型进行野外微动数据的采集,进而利用空间自相关法从微动信号中提取瑞雷波频散曲线,最后获得视S波速度剖面.通过与高密度电法探测结果对比发现微动探测方法在山区可以有效的识别隐伏构造和不同的岩性层、刻画高速异常地质体等.在灵活改变观测系统的情况下,针对山区公路建设对地质信息的要求,该方法可以提供关键的精细地质结构信息.通过本研究,初步证实了微动探测方法在山区探测的有效性,为后续复杂条件下的地球物理探测提供了新的有效探测手段. 相似文献
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活动断层高密度电法响应特征与应用研究 总被引：1，自引：0，他引：1
活动断层探测作为减轻地震灾害而开展的一项重要工作,一直被人们所关注.高密度电法已广泛应用于地质调查中,为了进一步认识高密度电法不同装置的探测效果及活动断层探测的高密度电法装置的有效选择,本文进行了温纳装置、二极装置、偶极—偶极装置、三极装置和温施装置的理论模型正反演研究,以及常用的温纳装置、温施装置和偶极—偶极装置的实例应用研究与分析.(1)基于断层是否穿过第四系判断断层活动的前提,理论模型模拟表明高密度各装置均可进行活动断层的定性探测和进行地质分层,而表层为相对高阻层的地层结构有利于进行地质分层,其精度高于表层为相对低阻层的地层结构;(2)模型模拟表明高密度偶极—偶极装置进行活动断层的定性探测和地质分层是最有效的装置,三极装置次之;(3)理论模拟和实例应用表明,高密度偶极—偶极装置对活动断层的响应最敏感,可有效确定其性质,这与理论模拟结果完全相符,因此实际应用时宜采用偶极—偶极装置进行活动断层的探测. 相似文献
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S波速度结构能够反映地球介质的物性差异,是地壳内低速区结构特征判别的重要依据.本文尝试利用空间自相关法(SPAC法)从地震台站微动信号的垂直分量中提取瑞利波相速度频散曲线,通过对频散曲线的反演获得地下介质的S波速度结构.以国家数字测震台网8个宽频带地震台站的实测微动数据为例,采用SPAC方法获得了首都圈地区北京附近约30 km 深度范围内的一维S波速度结构.结果表明,该区结晶基底埋深较浅约2 km;分别在5~8 km 和12~16 km 深处发育S波低速层;8 km 和 20 km 处是S波速度差异较大的速度分界面.这一结果与以往地震学及人工地震探测结果较为吻合,表明SPAC法估算地壳S波速度结构是可行、有效的. 相似文献
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介绍了运用微振动勘探方法探测隐伏断裂构造的方法和思路,并对郯庐断裂带两条分支断裂进行了试验性勘探．通过与人工地震勘探结果对比分析,发现微振动勘探方法对隐伏断裂构造具有较好的空间定位能力,其对岩性差异面形成的断裂定位误差与人工地震勘探结果相当; 又因其具有较大的勘探深度,因而可以有效揭示勘探区域下方地层及断裂的空间分布特征及其接触关系,这对于识别和确定断裂构造的主破裂面具有重要意义. 但微振动勘探方法对地层或断裂构造细节特征的揭示能力较差．因此,在实际地层或断裂勘探中,宜采用人工地震勘探方法与微振动勘探方法相结合的方式确定断裂的深浅构造关系,可以用微振动勘探方法进行普查,在确定断裂初步位置及空间展布特征后,再选用人工地震勘探方法进行断裂精确定位． 相似文献
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Microtremor Measurements for the Microzonation of Dinar 总被引：3，自引：0，他引：3
v--vThe geotechnical site conditions in Dinar town located in western Turkey were investigated after the 1995 Dinar earthquake based on borings, in situ penetration tests, seismic wave velocity measurements, and microtremor records. The variation of damage distribution within the town was evaluated with respect to 23 district damage ratios calculated, based on the detailed damage survey conducted by the General Directorate of Disaster Affairs. Site amplifications were estimated from microtremor spectral ratios and microzonation was performed using a GIS methodology. The results of in situ penetration tests and seismic wave velocity measurements as well as the damage distribution were compared with the amplification zonation obtained from microtremor records. The results indicate the applicability of microtremor spectral ratios for assessing the local site conditions and site amplifications. 相似文献
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J. Cid T. Susagna X. Goula L. Chavarria S. Figueras J. Fleta A. Casas A. Roca 《Pure and Applied Geophysics》2001,158(12):2559-2577
—?Seismic responses of different sites of Barcelona have been investigated through numerical modelling. Geological maps and geotechnical data available from drillings for buildings and infrastructures have been used to determine the dynamical properties of the soils through different correlations between standard geotechnical data and dynamical parameters obtained in other regions. An estimation of the depth of the Palaeozoic basement has been obtained through an inversion of a detailed gravity survey. A 1-D equivalent linear method has been used to compute complete transfer functions and other spectral responses, such as PSA and PSV for various damping values, with the purpose of classifying zones with similar behaviour. Given the uncertainties associated with the input data, a Montecarlo's simulation process has been carried out. Four zones, characterized by their corresponding transfer function and by PGA amplifications, are proposed. The numerical results are compared with those previously obtained through microtremor measurements, showing that predominant periods derived from Nakamura's technique should be taken carefully. 相似文献
14.
Earthquake has left much life and property damages. The occurrence of such events necessitates the execution of plans for combating the earthquakes. One of the most important methods for combating earthquakes includes assessing dynamic characteristics of soil and site effect. One of the methods by which one can state dynamic characteristics of the soil of an area is the measurement of microtremors. Microtremors are small-scale vibrations that occur in the ground and have an amplitude range of about0.1–1 microns. Microtremor measurement is fast, applicable, cost-effective. Microtremor measurements were taken at 15 stations in the Babol, north of Iran. Regarding H/V spectral ratio method, peak frequency and amplification factor were calculated for all microtremor stations.According to the analysis, the peak frequency varies from0.67 to 8.10 Hz within the study area. Also, the authors investigated the validity of the results by comparing them with SESAME guidelines and geotechnical conditions of study area. The microtremor analysis results are consistent with SESAME guidelines and geotechnical condition of study area. The results show that the microtremor observations are acceptable methods for assessing dynamic characteristics of soil and site effect in the Babol City. 相似文献
15.
Paolo Boncio Sara Amoroso Giovanna Vessia Marco Francescone Mauro Nardone Paola Monaco Daniela Famiani Deborah Di Naccio Alessia Mercuri Maria Rosaria Manuel Fabrizio Galadini Giuliano Milana 《Bulletin of Earthquake Engineering》2018,16(1):91-111
In this study, we analyse the susceptibility to liquefaction of the Pozzone site, which is located on the northern side of the Fucino lacustrine basin in central Italy. In 1915, this region was struck by a M 7.0 earthquake, which produced widespread coseismic surface effects that were interpreted to be liquefaction-related. However, the interpretation of these phenomena at the Pozzone site is not straightforward. Furthermore, the site is characterized by an abundance of fine-grained sediments, which are not typically found in liquefiable soils. Therefore, in this study, we perform a number of detailed stratigraphic and geotechnical investigations (including continuous-coring borehole, CPTu, SDMT, SPT, and geotechnical laboratory tests) to better interpret these 1915 phenomena and to evaluate the liquefaction potential of a lacustrine environment dominated by fine-grained sedimentation. The upper 18.5 m of the stratigraphic succession comprises fine-grained sediments, including four strata of coarser sediments formed by interbedded layers of sand, silty sand and sandy silt. These strata, which are interpreted to represent the frontal lobes of an alluvial fan system within a lacustrine succession, are highly susceptible to liquefaction. We also find evidence of paleo-liquefaction, dated between 12.1–10.8 and 9.43–9.13 kyrs ago, occurring at depths of 2.1–2.3 m. These data, along with the aforementioned geotechnical analyses, indicate that this site would indeed be liquefiable in a 1915-like earthquake. Although we found a broad agreement among CPTu, DMT and shear wave velocity “simplified procedures” in detecting the liquefaction potential of the Pozzone soil, our results suggest that the use and comparison of different in situ techniques are highly recommended for reliable estimates of the cyclic liquefaction resistance in lacustrine sites characterized by high content of fine-grained soils. In geologic environments similar to the one analysed in this work, where it is difficult to detect liquefiable layers, one can identify sites that are susceptible to liquefaction only by using detailed stratigraphic reconstructions, in situ characterization, and laboratory analyses. This has implications for basic (Level 1) seismic microzonation mapping, which typically relies on the use of empirical evaluations based on geologic maps and pre-existing sub-surface data (i.e., age and type of deposits, prevailing grain size, with particular attention paid to clean sands, and depth of the water table). 相似文献
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Every year, numerous casualties and a large deal of financial losses are incurred due to earthquake events. The losses incurred by an earthquake vary depending on local site effect. Therefore, in order to conquer drastic effects of an earthquake, one should evaluate urban districts in terms of the local site effect. One of the methods for evaluating the local site effect is microtremor measurement and analysis. Aiming at evaluation of local site effect across the city of Babol, the study area was gridded and microtremor measurements were performed with an appropriate distribution. The acquired data was analyzed through the horizontal-to-vertical noise ratio (HVNR) method, and fundamental frequency and associated amplitude of the H/V peak were obtained. The results indicate that fundamental frequency of the study area is generally lower than 1.25 Hz, which is acceptably in agreement with the findings of previous studies. Also, in order to constrain and validate the seismostratigraphic model obtained with this method, the results were compared with geotechnical, geological, and seismic data. Comparing the results of different methods, it was observed that the presented geophysical method can successfully determine the values of fundamental frequency across the study area as well as local site effect. Using the data obtained from the analysis of microtremor, a microzonation map of fundamental frequency across the city of Babol was prepared. This map has numerous applications in designing high-rise building and urban development plans. 相似文献