姚安6.5级地震场地与震害的关系

介绍了姚安6．5级地震震区地质概貌和场地特征。以100多个现场调查点资料为基础，将影响震害的四种主要因素，按其影响轻重分类，用震害指数分析了该次地震的震害分布和局部场地特征对震害的影响。结果表明，震区未形成震害异常区，但有震害异常点存在。在影响震害的诸多场地因素中，以地基土特性的影响最为严重。     

远震作用下软弱土层的震害影响

软弱土层在地震作用下,容易发生水平永久变形和不均匀沉陷,是发生震害的主要因素之一。特别是在远震作用下,软弱土层地区的破坏烈度高于其他较坚硬岩土地区,软弱土层上部的中高层建筑物和构筑物更易遭受破坏。通过回顾和分析1994年9月16日台湾海峡7.3级地震在汕头市的地震反应特征及震害影响,指出应加强软弱土层地区的工程抗震设计,提高防灾抗震能力。     

威海震害地质区划

为了做好城市建设规划,应及时提供震害预测资料。尽管影响震害的因素很多,但就其区域分布而言,明显地受着地质条件的制约,这已为许多历史地震资料所证实。这种因地质条件差异而形成的烈度区划谓之震害地质区划,它有着广泛的现实意义。一、震害地质区划的原则震例调查表明,影响震害地质区划的因素主要有:1、断层:主要指发震断层,或具有新构造活动特征的断层,这种断层形成的地质历史长、规模大,岩石破碎,充水,震害效应明显。1948年威海发生六级地震时地裂、     

彝良5.7、5.6级地震烈度分布及烈度异常区震害特征初步分析

根据彝良5.7、5.6级地震现场震害调查资料,介绍了地震烈度分布及各烈度区的震害特征;描述了两个烈度异常区17个点、4250户调查点的详细震害情况,对异常区震害特点进行了分析,并从地质构造、含煤地层、地形地貌及岩土性质、房屋建筑结构及质量等方面对震害异常原因进行了初步分析与探讨,提出了异常区恢复重建需考虑的不利因素.     

施甸5.9级地震场地与震害的关系

施甸5．9级地震震源浅导致了其震害偏重，而特殊的场地条件则导致许多烈度异常区（点）的产生。概述了施甸县历史地震的情况，介绍了旋甸5．9级地震震区自然根貌和场地特征，以近百年现场调查点资料为基础，将影响震害的四种主要因素，按其对震害影响程度的轻重分类，分析了该次地震的震害分布特征与异常区的场地特征，结果表明，在影响震害的诸多场地因素中，以地基土特性的影响最重。     

鲁甸5.6级地震震害分析

通过对云南鲁甸5．6级地震中47个居民点的震害调查，给出了本次地震的等烈度分布图，分析了场地条件与震害的关系、各类房屋的震害特征、典型房屋震害累积效应以及生命线工程震害。结果表明：这次地震比2003年11月鲁甸5．1、5．0级两次地震破坏严重，形成了Ⅷ度破坏区及较大范围的Ⅶ度和Ⅵ度破坏区，盆地区的震害比基岩区的要重．其主要原因是：①盆地区广泛分布有软弱地层；②震区建筑结构简易，抗震能力极差；③三次地震震区基本重叠，震害累积效应表现突出。     

山西忻定盆地震害地质条件及其与未来震害关系的研究

本文详细地论述了忻定盆地的地形、地貌、断层活动、土层岩性、土层的平均剪切模量、地下水埋深、历史地震和震害,特别是1952年原平崞阳地震时震害类型及其分布特征。并根据未来地震活动和强度、震害地质条件以及历史震害分布规律,将工作区划分为六个震害区;各震害区未来强震时将会出现不同的震害类型和类型组合,震害强度也将会有所不同。这些成果可为忻定盆地城乡规划及重点工程建设提供抗震防震依据。     

四川筠连M_S4.9地震震害特征及致灾因素分析

根据四川筠连M_S4.9地震现场震害调查资料,总结震区各类房屋震害特征及典型地震地质震害情况,结合区域地质构造环境、震源机制解和余震序列,初步探讨震害分布特征及破坏机理。研究结果表明,震区多数房屋为砖混结构,其整体破坏情况较砖木和土木结构房屋重;震区地震地质灾害受高差、坡度和岩性影响较强。震害破坏程度较重的主要因素包括:房屋结构不合理、抗震性能低;场地地基软弱或存在临空面,不均匀沉降现象突出;地质构造环境复杂,震害"上、下盘效应"明显;短时间段内地震频发,震害累积效应显著;人文地理环境限制,屋顶蓄水增强荷载不均匀现象。     

唐山市古冶区预测震害烈度的确定

通过分析唐山市古冶区地震地质资料、历史地震资料并结合唐山市7.8级大地震强余震的分布规律等,综合确定唐山古冶区预测震害烈度,为房屋震害预测分析提供依据。     

唐山市新区预测震害烈度的确定

通过分析唐山市新区地震地质资料、历史地震资料并结合唐山大地震与强余震的分布规律等，综合确定唐山新区预测震害烈度，为房屋震害预测分析提供依据。     

基于正交设计的红层软岩改良土压缩模量试验研究

西部地区大型基础性工程项目日益增多,为处理工程开挖出的大量土方,减少工程造价和实现绿色发展的目标,通过对红层软岩改良土进行试验研究,评价其作为路基回填料的可行性.以西北某地铁深基坑项目为依托,首先通过对不同黄土和水泥掺比下红层软岩改良土进行正交试验研究,其次对该改良土压缩模量的影响因素进行分析,并给出最佳配合比,最后对...     

用美国西部强震记录讨论厚覆盖土层峰值加速度的放大效应

以美国西部强震观测数据资料为基础,分别建立基岩和厚土层上的峰值加速度衰减规律,探讨厚土层对基岩峰值加速度的放大作用.结论为:平均而言,对美国西部这样的厚土层峰值加速度放大作用不大.但基岩峰值加速度越大,厚土层放大作用越小;震中距越远,厚土层放大作用越大.     

跨断层形变监测标石地岩土分类探讨

分析了跨断层形变监测标石地岩土分类、地表岩土分类、影响监测场地标石稳定因素以及不同监测标石地监测实例变化等。结果表明：现有监测标石地岩土分类需要完善;重新分类了监测标石地岩土并给出了监测标石命名方法,以期促进跨断层形变监测工作进一步发展。     

基于FLAC^3D的锚索抗滑桩滑坡推力分布规律研究

采用FLAC^3D建立了预应力锚索桩板墙结构的三维数值模型,结合有限元强度折减法分析了不同预应力作用下锚索桩滑坡推力的分布规律,并通过改变桩后岩土体的弹性模量及性质、锚索的设置位置以及边坡强度安全储备系数等参数,对锚索桩滑坡推力的分布规律进行了系统的研究。结果表明,在地质条件不变的情况下,随着锚索预应力的增大,桩后滑坡推力的分布图形逐渐由梯形向矩形变化;预应力对桩后滑坡推力分布的影响,取决于其与桩背总桩土相互作用力的相对大小,而不是其绝对大小。说明预应力的大小是影响桩后推力分布形式的一个非常重要的因素,照搬普通抗滑桩固定不变的推力分布形式对锚索桩进行设计,显然是不合理的。     

CONTROLLING FACTORS AND MECHANISMS OF INCOMPLETE OBSTRUCTION SEISMIC LANDSLIDE MOBILITY

The topography, occurrence mechanism and lithology are the important factors of landslide movement. The lithology, seismic intensity, geological structure and topography in the travel path of 215 incomplete obstruction landslides with volumes more than 10⁴m³ induced by Wenchuan earthquake were studied. Based on the classification of the factors established, we studied the factors influencing the movement distance of incomplete obstruction landslides. The following results are drawn. In the influence factors of topography in the travel path, the distance is largest in the straight valley topography, followed by the concave, ladder, turning valley, slope toe-type and slope-type landslides, in turn. The topography not only has remarkable influence on the distance of large-scale landslides, but also on the medium and small-scale landslides as well, which is the most important factor influencing the distance. The formation mechanism controlled by lithology, seismic intensity and geological structure has little influence on the mobility of medium-and small-scale landslides. For the large-scale landslides with volume more than 10⁶m³, the distance of landslide with medium hard rock is larger than landslides with hard and soft rock. In the seismic intensity Ⅸ to Ⅺ areas, the landslide distance decreases with intensity increasing, contrary to the distribution of landslide-point density and landslide-area density. The geological structure has influence on the slide aspect of landslides and occurrence mechanism, but the influence is not remarkable to the landslide movement distance.     

Surface Soil Effects Study Using Short-period Microtremor Observations in Almería City, Southern Spain

—?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.     

Side effect of using response spectral amplification ratios for soil sites—variability and earthquake-magnitude and source-distance dependent amplification ratios for soil sites

We investigate a special type of variability in response spectral amplification ratios computed from numerical “engineering” models for a soft soil site. The engineering models are defined by shallow soil layers over “engineering” bedrock with a shear-wave velocity over 600–700 m/s and the model is subjected to vertical propagating shear waves. The variability, perhaps unique in earthquake engineering, is a result of the “perfectly accurate” computational procedure. For example, an engineering soil site model, subjected to two rock site records or the two horizontal components of a rock site record, produces different response spectral amplification ratios. We use a large number of strong-motion records from “engineering” rock sites, with a reasonably balanced distribution with respect to magnitude and source distance, generated by subduction earthquakes in Japan, to investigate the nature of the variability. In order to avoid any approximation in removing the effect of soil nonlinear response, we use a simple model, a single horizontal soil layer over a bedrock, modelled as elastic. We then demonstrate that a similar type of variability observed in the one- or two-dimensional nonlinear soil models is caused by the nature of response spectral amplification ratios, not a direct result of soil nonlinear response. Examination of variability reveals that the average of response spectral amplification ratios systematically depends on both earthquake magnitude and source distance. We find that, at periods much longer than the site natural periods of the soil sites, the scatter of the amplification ratios decreases with increasing magnitude and source distance. These findings may have a potential impact in establishing design spectra for soft soil sites using strong-motion attenuation models or dynamic numerical modelling.     

输水隧道的减震措施研究

隔震技术是近几十年发展起来的新技术,对地面结构减震效果显著。本文运用Newmark隐式时间积分有限元法并采用粘-弹性人工边界,分析了在输水隧道施工中设置减震层和注浆加固一定范围内围岩这2种方法的减震效果、适用条件及其减震机理。计算结果表明：减震层或加固层的设置均使隧道衬砌应力减小,起到保护隧道衬砌的作用;在较大的范围内注浆加固围岩的办法,对软土中的输水隧道的减震更加有效,它能充分发挥围岩的承载能力;而在围岩与衬砌间设置减震层的办法,对稳定性极好的坚硬围岩中的输水隧道的减震效果更加有效。计算结果可为地震区的输水隧道抗震设计提供依据。     

珠江三角洲场地震害预测

场地震害是随空间和时间而变化的多因子影响的综合体。本文根据这一观点分析影响珠江三角洲场地震害的环境因子及岩土特征，探讨该区砂土液化、软土震陷、活动断裂、滑坡、崩塌、岩溶和孤立地形等场地震害，指出本区未来场地震害的主要形式是砂土液化和软土震陷，但也不可忽视活动断裂和水下场地震害，以及特殊地形地貌引致的共振、驻波破坏。