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1.
<正>研究表明,只有当某个地区发生震级足够大的地震,这一地区才有可能产生场地液化现象。震级小于或者等于5.5级的地震,即使极震区烈度为Ⅶ度,其场地液化则难以发生或者说场地液化震害的影响有限。但是,对于7.5级左右的(特)大地震,由于地震动持续时间长,震动次数多,需要考虑远场甚至是Ⅵ~Ⅴ度区内液化的发生及其引起的破坏。因此,要反映地震强度和地震持续时间对液化的确切影响,仅以烈度概括是不够的,应以震级定量化,这样可以为地震现场工作人员评估场地液化震害奠定基础。结合地震震  相似文献   

2.
青海玛多7.4级地震发生后,本文作者随科考队开展了典型工程的震害调查。本文报道了黄河乡江旁村和昌马河工区这2个典型调查点的建筑震害情况。调查表明:邻近微观震中的黄河乡建筑震害程度相对较轻,主要表现为部分房屋落瓦,砖混结构少数承重墙及框架结构部分隔墙开裂,土木结构房屋部分严重破坏,部分围墙倒塌;而距微观震中以东85 km的昌马河工区建筑震害则相对较重:无抗震措施的砖木结构房屋全部严重破坏或倒塌,具备合理抗震措施的砖混结构基本完好或轻微破坏,在建轻钢厂房均钢柱倾斜、维护墙明显开裂并且围墙多数倒塌。调查分析表明:造成两地震害差异的主要原因为抗震措施差异以及地表破裂和砂土液化影响:黄河乡多数房屋具备合理抗震措施,昌马河工区多数民居缺少抗震措施;昌马河工区附近发现疑似地表破裂痕迹,而紧邻黄河乡的河岸发现砂土液化迹象。这表明昌马河工区的地震作用中类似近场的高频能量可能较多,而黄河乡地区则因砂土液化使得高频地震动作用有所降低,由此造成两地震害程度与震中距呈现反差关系。  相似文献   

3.
地震液化区的桥台震害是桥梁结构的一种重要震害形式。以1976年唐山地震中发生震害的胜利桥为例,采用UWLC软件对胜利桥震害进行了数值模拟分析。研究液化场地重力式桥台的震害模式与地震响应,并将数值模拟结果与实际震害结果进行了对比验证;研究了桥台顶端侧向约束力和桥台底部液化层厚度对桥台震害模式的影响,并对桥台的两种不同地基处理措施的抗震效果进行了分析。研究结果表明:数值模拟结果与实际震害结果基本一致;梁的约束力对桥台的震害模式影响较大,进行桥台震害分析应考虑梁的约束力作用;桥台底部液化层厚度对桥台的震害模式影响不大。  相似文献   

4.
公路桥区域性震害预测   总被引:8,自引:1,他引:8  
地震区桥址地基失效或岸坡失稳,对于桥梁的震害程度有明显的影响。本文基于这一特点,将历史地震桥梁震害资料,依据无液化场地及可液化场地或岸坡失稳的影响,分别以几个主要灾害影响因素对应于不同震害程度进行数理统计,并应用模糊数学方法,综合评判在未来地震中大面积范围桥梁可能出现的震害状态,它对于地震区部署桥梁的抗震防灾工作有着重要的现实意义。  相似文献   

5.
西北农居震害构成及抗震性能综合影响因素分析   总被引:1,自引:1,他引:0       下载免费PDF全文
整理西北地区部分地震的震害资料,对西北五省的主要农居进行震害总结,分析不同结构农居震害和抗震性能,发现不同结构的抗震性能差别较大,并针对不同结构提出相应的防震减灾措施。从地震动特性、场地和地基基础、结构的自身特性等方面分析影响农居民房的抗震能力,并根据西北农居震害特点给出了防震减灾方面的一些建议。  相似文献   

6.
汶川大地震液化的特点及带来的新问题   总被引:1,自引:0,他引:1  
总结汶川8.0级大地震液化及其震害科学考察结果,分析此次地震液化带来的新问题.结果表明,汶川大地震中液化及其震害现象显著,是建国以来液化涉及区域最广、液化宏观现象最为丰富的一次;本次地震液化宏观现象特点为喷水高、持时短、喷砂量小但喷砂类型十分丰富;砂砾土液化、Ⅵ度区内场地液化、深层土液化、无液化减震以及液化普遍伴随地裂缝是此次地震液化5个突出特征;砂砾土液化判别技术、液化引起地表裂缝机理和预测方法、Ⅵ度区内场地液化与深层土的液化机理和预测方法、液化加减震发生条件、场地液化现场判定与识别技术等是新的课题.为解决上述问题,应优先发展岩土地震工程观测技术及建设岩土地震工程实验场.  相似文献   

7.
我国抗震规范砂土液化初判条件中,若砂层上覆土层深度超过特征深度即判为不液化或不考虑液化影响,利用近期地震液化调查数据对其适用性进行了检验。采用1995年日本阪神地震和1999年台湾集集地震的液化调查资料,发现我国规范液化判别特征深度取值会产生不可忽视的误判,而造成偏于危险的结果;采用2011年新西兰Ms6.3级地震液化调查资料,初步估计按我国规范液化判别特征深度取值会将65%的液化场地判为非液化场地,严重偏于危险。因此我国规范液化初判条件液化特征深度取值已不适用,需要研究改进。  相似文献   

8.
汶川8.0级地震甘肃陇南地区建筑震害调查   总被引:3,自引:3,他引:0       下载免费PDF全文
总结了2008年汶川8.0级地震在甘肃陇南地区造成的农村房屋和城镇房屋的典型震害及其原因。考察发现,由于农村房屋一般未经抗震设防设计,在本次地震中即使在低烈度地区仍然震害严重;而城镇房屋震害较轻,一般均表现出良好的抗震性能,严重破坏的大多是一些施工质量差,缺乏良好的抗震概念设计以及改建时未考虑抗震设计的建筑。建筑震害调查的几个地区设防烈度均为Ⅷ度,实际烈度为Ⅵ~Ⅸ度,因此这些地区的房屋震害情况刚好能反映这些地区房屋抵抗小震、中震及大震的能力。结果表明,严格按照抗震规范设计、并保证施工质量的建筑基本都能达到三水准设防目标。最后本文对灾后重建和抗震设防提出了建议。  相似文献   

9.
以2003年2月24日新疆巴楚-伽师地区液化调查为基础。检验国内外现有以标准贯入击数试验为指标的液化判别方法的适用性,包括我国规范液化判别方法和Seed-Idriss方法。检验结果表明,我国规范和Seed-Idriss方法在对巴楚地震液化场地判别成功率较低,总体成功率均为66%,非液化场地的判别成功率分别为85%和84%,但对液化场地判别成功率仅为43%和48%,明显偏于危险。原因可能是标贯形成数据主要来源其它地区而巴楚地区砂土与之差异较大所致,值得深入研究。  相似文献   

10.
珠江三角洲场地震害预测   总被引:3,自引:2,他引:3  
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。  相似文献   

11.
龚平 《地震地质》2002,24(2):278-287
在地震活动性参数估计中 ,对同一地区具有相同地震资料和相同统计方法的情况下 ,活动性参数会出现因人而异的估计结果。为了对这些参数的不同估计做出评价 ,文中从统计角度将似然比检验引入到地震活动性参数的不同估计的选优排序决策中 ,分析了似然比检验的基本特征 ,并以华北地区为例示范性地分析了似然比检验对地震活动性参数的决策性检验  相似文献   

12.
The Canterbury region experienced widespread damage due to liquefaction induced by seismic shaking during the 4 September 2010 earthquake and the large aftershocks that followed, notably those that occurred on 22 February, 13 June and 23 December 2011. Following the 2010 earthquake, the Earthquake Commission directed a thorough investigation of the ground profile in Christchurch, and to date, more than 7500 cone penetration tests (CPT) have been performed in the region. This paper presents the results of analyses which use a subset of the geotechnical database to evaluate the liquefaction process as well as the re-liquefaction that occurred following some of the major events in Christchurch. First, the applicability of existing CPT-based methods for evaluating liquefaction potential of Christchurch soils was investigated using three methods currently available. Next, the results of liquefaction potential evaluation were compared with the severity of observed damage, categorised in terms of the land damage grade developed from Tonkin & Taylor property inspections as well as from observed severity of liquefaction from aerial photography. For this purpose, the Liquefaction Potential Index (LPI) was used to represent the damage potential at each site. In addition, a comparison of the CPT-based strength profiles obtained before each of the major aftershocks was performed. The results suggest that the analysis of spatial and temporal variations of strength profiles gives a clear indication of the resulting liquefaction and re-liquefaction observed in Christchurch. The comparison of a limited number of CPT strength profiles before and after the earthquakes seems to indicate that no noticeable strengthening has occurred in Christchurch, making the area vulnerable to liquefaction induced land damage in future large-scale earthquakes.  相似文献   

13.
进行地震灾害快速评估时,地震发生时刻、震级、极震区烈度评估、宏观震中与微观震中偏离、烈度衰减关系模型、人员伤亡评估模型、房屋震害矩阵等是影响地震灾害损失计算的主要因素,各因素存在不确定性,所以评估结果与实际结果存在一定差距。本文探讨了2020年1月19日新疆伽师6.4级地震灾害评估中极震区烈度评估、地震影响场、宏观震中与微观震中偏离、烈度衰减关系模型、人员伤亡评估模型、房屋震害矩阵与真实结果的偏差。研究结果表明,造成本次地震损失快速评估结果存在偏差的主要因素包括地震影响场分布、人口与房屋建筑(对应抗震能力)数量评估的偏差;提高地震影响场评估、人口、房屋建筑等数据空间分布精准性,是提高地震灾害损失快速评估系统精准性的基础和前提。  相似文献   

14.
不同抗震设计规范的砂土液化判别方法或国内外其他有代表性的液化判别方法所采用的地震动参数和土性指标及其埋藏条件是不同的,因而采用这些方法对同一工程场地进行液化势预测时其评价结果通常有一些差异,甚至会得到相反的结论。为了给重大工程建设提供较为合理、可信的地基液化势预测结果,采用多种液化判别方法进行场地液化势的综合评价是比较客观的,也是必要的。本文结合某长江大桥桥基工程,采用建筑抗震设计规范的砂土液化判别方法、国内外有代表性的液化判别方法、有限元数值分析法等多种方法逐一对该工程场地砂性土层进行液化判别,并结合室内动三轴液化试验结果,对主桥墩不考虑冲刷条件和考虑一般冲刷深度5m条件时的砂性土层进行了液化势的综合评价,并将各土层的液化势分为液化、可能液化和不液化3个等级,得到了较为合理可靠的判别结果。  相似文献   

15.
何蔚 《华南地震》1997,17(4):73-77
通过对昆明经济技术开发区的地质构造,场地工程地质环境,砂土液化判别以震害预测的综合研究,进行了区内的场地地震易损性分析。根据计算出的地震易损性指数,结果表明,可将研究区划分为两个震害程度不同的区域。  相似文献   

16.
Estimating the possible region of liquefaction occurrence during a strong earthquake is highly valuable for economy loss estimation, reconnaissance efforts and site investigations after the event. This study identified and compiled a large amount of liquefaction case histories from the 2008 Wenchuan earthquake, China, to investigate the relationship between the attenuation of seismic wave energy and liquefaction distance limit during this earthquake. Firstly, we introduced the concept of energy absorption ratio, which is defined as the absorbed energy of soil divided by the imparted energy of seismic waves at a given site, and the relationship between the energy absorption ratio and the material damping ratio was established based on shear stress–strain loop of soil element and the seismic wave propagation process from the source to the site. Secondly, the threshold imparted seismic energy of liquefaction was obtained based on existing researches of absorbed energy required to trigger liquefaction of sandy soils and the ground motion attenuation characteristics of the 2008 Wenchuan earthquake, and the liquefaction distance limit of this earthquake was estimated according to the proposed magnitude–energy–distance relationship. Finally, the field liquefaction database of 209 sites of the 2008 Wenchuan earthquake was used to validate such an estimation, and the field observed threshold imparted seismic energy to cause liquefaction in recent major earthquakes worldwide was back-analyzed to check the predictability of the present method, and several possible mechanisms were discussed to explain the discrepancy between the field observations and the theoretical predictions. This study indicates that seismic energy attenuation and liquefaction distance limit are regional specific and earthquake dependent, and 382 J/m3 is the average level of threshold imparted seismic energy to cause liquefaction for loose saturated sandy soils, and the corresponding liquefaction distance limit is approximately 87.4 km in fault distance for a Mw?=?7.9 event in the Chengdu Plain. The proposed regional energy attenuation model and threshold imparted seismic energy may be considered as an approximate tool in evaluating the liquefaction hazard during potential earthquakes in this area.  相似文献   

17.
Many different types of buildings were severely damaged or collapsed during the May 12, 2008 Great Wenchuan Earthquake. Based on survey data collected in regions that were subjected to moderate to severe earthquake intensities, a comparison between the observed building damage, and the three earthquake performance objectives and seismic conceptual design principles specified by the national "Code for Seismic Design of Buildings GB50011-2001," was carried out. Actual damage and predicted damage for a given earthquake level for different types of structures is compared. Discussions on seismic conceptual design principles, with respect to multiple defense lines, strong column-weak beam, link beam of shear walls, ductility detailing of masonry structures, exits and staircases, and nonstructural elements, etc. are carried out. Suggestions for improving the seismic design of structures are also proposed. It is concluded that the seismic performance objectives for three earthquake levels, i.e., "no failure under minor earthquake level, ""repairable damage under moderate earthquake level" and "no collapse under major earthquake level" can be achieved if seismic design principles are carried out by strictly following the code requirements and ensuring construction quality.  相似文献   

18.
It has taken more than a hundred years for seismic observations in the Philippines to evolve to a modern observation system.The responsibility of seismic observations was likewise transfeered from one agency to another during this same period of time.At present,the mandate of conducting seismic observatins in the Philippines rests with the Philippine Institute of Volcanology and Seismology(PHIVOLCS),In 2000,through a grant aid from the Japan International Cooperation Agency(JICA),the Philippine Seismic netowrk was upgraded to a digital system.As a result,a new set of seismic monitoring equipments was installed in all of the 34 PHIVOLCS seismic stations all over the country,Digital waveforms are now available for high level seismic data processing.and data acquisition and processing are now automated.Included in the upgrade is the provision of strong motion accelerographs in all stations whose data can now be used for studying ground motion and intensity attenuation relations,The new setup is now producing high-resolution data that can now be used for conducting basic seismological researches,Earthquake locations have now improved allowing for the modeling and delineation of earthquake source regions necessary for earthquake hazard studies.Current seismic hazard studies in the Philippines involve the estimation of ground motion using both probabilitstic and deterministic approaches,seismic microzonation studies of key cities using microtremor observations,paleoseismology and active faults mapping ,and identification of liquefaction-prone,landslide-prone nd tsunami-affected areas.The earthquake database is now being reviewed and completed with the addition of historical events and from data from regional databases,While studies of seismic hazards were primarily concentrated on a regional level ,PHIVOLCS is now focusing on doing these seismic hazard studies on a micriolevel.For Metro Manila,first generation hazard maps showing ground rupture,ground shaking and liquefaction hazards have recently been completed.Other large cities that are also at risk from large earthquakes are the next targets.The elements at risk such as population,lifelines,and vertical and horizontal structures for each of these urban centers are also being incorporated in the hazard maps for immediate use of planners,civil defense officials,policy-makers and engineers.The maps can also now be used to describe possible scenarios during times of strong events and how appropriate socio-economic and engineering responses could be designed.In addition,a rapid earthquake damage assessment system has been started which will attempt to produce immediate or rapid assessments identification of elements at risk durin times of strong earthquakes  相似文献   

19.
汶川地震中梁式桥的震害和预防震害的新方法   总被引:6,自引:0,他引:6  
本文基于地震现场考察资料介绍了汶川地震中梁式桥的一些典型震害实例,分析震害原因及其发生规律,并探讨强烈地震作用下防震害的新方法。新方法是以适当的构造方式改变地震能量的传输,减少桥面系与墩台的相对位移,保证下部结构的安全,从而达到防止震害的目的。  相似文献   

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