Seismic vulnerability assessment to slight damage based on experimental modal parameters

The aim of this paper is to adjust behaviour models for each class of structure for vulnerability assessment by using ambient vibration. A simple model based on frequencies, mode shapes and damping, taken from ambient vibrations, allows computation of the response of the structures and comparison of inter‐storey drifts with the limits found in the literature for the slight damage grade, considered here as the limit of elastic behaviour. Two complete methodologies for building fragility curves are proposed: (1) using a multi‐degree of freedom system including higher modes and full seismic ground‐motion and (2) using a single‐degree of freedom model considering the fundamental mode f₀ of the structure and ground‐motion displacement response spectra S_D(f₀). These two methods were applied to the city of Grenoble, where 60 buildings were studied. Fragility curves for slight damage were derived for the various masonry and reinforced concrete classes of buildings. A site‐specific earthquake scenario, taking into account local site conditions, was considered, corresponding to an M_L = 5.5 earthquake at a distance of 15 km. The results show the benefits of using experimental models to reduce variability of the slight damage fragility curve. Moreover, by introducing the experimental modal model of the buildings, it is possible to improve seismic risk assessment at an overall scale (the city) or a local scale (the building) for the first damage grade (slight damage). This level of damage, of great interest for moderate seismic‐prone regions, may contribute to the seismic loss assessment. Copyright © 2011 John Wiley & Sons, Ltd.     

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张性断裂带内部结构特征及油气运移和保存研究

断裂带是一个宽度、长度和高度均与断距呈正比关系的三维地质体,具有典型的二分结构：即断层核和破碎带。断层核由多种类型的断层岩和后期胶结物组成,具有分选差,粘土含量高,颗粒粒径小等特征,表现为具有比围岩更低的孔渗性。破碎带同围岩相比发育大量的裂缝,裂缝的密度随着离断层核距离的增大而逐渐减小,孔渗性较高。断层岩类型取决于断移地层的岩性、成岩程度和断裂变形时期。对于同生断层而言,泥岩和不纯净的砂岩主要发生泥岩涂抹作用;纯净砂岩发生解聚作用,形成颗粒重排的变形带。中成岩阶段发生断裂变形,泥岩发生泥岩涂抹作用,不纯净的砂岩发生碎裂作用和层状硅酸盐涂抹作用,形成碎裂岩和层状硅酸盐 框架断层岩;纯净砂岩主要发生碎裂作用,形成碎裂岩。晚成岩阶段发生断裂变形,碎裂作用成为主要的变形机制,泥岩破碎形成大量断层泥,不纯净的砂岩和纯净的砂岩均形成碎裂岩,其中纯净砂岩形成的碎裂岩由于石英的压溶胶结变得更致密。因此不同成岩阶段、不同岩性形成的断层岩类型不同,泥岩涂抹的排替压力高于层状硅酸盐 框架断层岩和碎裂岩,即使都是碎裂岩,其渗透率相差7个数量级。从断裂带结构看油气运移和保存,断层垂向封闭主要靠剪切型泥岩涂抹的连续性,侧向封闭能力取决于断层岩物性,物性很高的碎裂岩自身封闭能力很差,依靠两盘岩性对接封闭油气,最小断距决定油水界面位置。物性很低的断层岩一般能封住一定高度的油气柱,其是断裂带中泥质含量的函数。断层在储盖层段变形机制差异,决定了断裂输导与封闭油气的耦合,即破碎带双向输导充注,盖层段剪切型泥岩涂抹顶部封闭,断层核遮挡成藏。     

跨越断层地下管线震害因素分析

地下管线抗震安全性问题是生命线地震工程的重要研究内容,大量震害表明地下管线,特别是跨越断层的地下管线具有极大的脆弱性。分析跨断层地下管线的震害影响因素,制定有效的工程措施对于提高实际地下管线的抗震性能具有重要意义。本文回顾了地下管线遭受震害的历史背景,主要从断层参数、地震及场地参数以及管道参数三个角度分析了影响跨越断层地下管线震害的因素。在这些震害因素分析以及前人工作总结的基础上,从宏观角度和具体措施两个方面,提出了一些跨断层地下管道抗震的措施。     

基于统计损伤的岩爆预测

基于岩石单轴抗压强度的分布特征,对脆性岩石采用统计损伤的平行杆模型模拟,经岩石全过程曲线拟合,表明了 模型的合理性。进而提出采用平行杆模型模拟地下深埋洞室脆性围岩,推出了不同应力条件下岩体损伤的表达式,从统计损 伤的概念上,利用损伤变量来表征岩爆发生概率。工程实例分析表明该预测方法是有效的。     

油水井套管损坏的地质因素综合研究

套管损坏一直是影响油田正常生产的严重干扰因素．其中地质因素是导致套管损坏的内在因素.塑性岩层发育段、断层破碎带等地质环境和地震、地层沉降等地质活动中易造成油水井的套管损坏。研究了套管损坏与盐类岩层及泥质岩的蠕变、滑移的关系;并从地应力变化的角度分析了构造因素如地层倾角和断层等对套管损坏的影响;还研究了地震和地层沉降等自然诱发因素,分析了高压注水和油层出砂等工程诱发因素对套管损坏的影响。     

Detecting temporal trends and environmentally-driven changes in the spatial distribution of bottom fishes and crabs on the eastern Bering Sea shelf

This study uses a 30-year time series of standardized bottom trawl survey data (1982–2011) from the eastern Bering Sea shelf to model patterns of summer spatial distribution for various bottom fishes and crabs in response to changes in the areal extent of the cold pool, time lag between surveys, and fluctuations in population abundance. This investigation is the first to include data for the 2006–2010 cold period and to use between-year comparisons of local and shelf-wide spatial indices to test specific responses to three different isothermal boundaries within the cold pool. Distributional shifts in population varied considerably among species and directional vectors for some species were greater in magnitude to the east or west than to the north or south; however, in general, eastern Bering Sea shelf populations shifted southward in response to the increasing cold pool size, and after accounting for differences in temperature and population abundance, there was still a temporal northward shift in populations over the last three decades despite the recent cooling trend. Model results for local and shelf-wide indices showed that survey time lag and cold pool extent had a greater effect on spatial distribution than population abundance, suggesting that density-independent mechanisms play a major role in shaping distribution patterns on the eastern Bering Sea shelf. The area enclosed by the 1 °C isotherm most commonly affects both local and shelf-wide spatial indices suggesting that 1 °C is a more important boundary for describing temperature preferences of eastern Bering Sea bottom fishes and crabs than is the 2 °C isotherm used for designating the physical boundary for the cold pool.     

Genotoxicity in two bivalve species from a coastal lagoon in the south of Portugal

DNA damage was evaluated by comet assay in the haemolymph of two bivalve species Ruditapes decussatus and Mytilus galloprovincialis from the Ria Formosa lagoon (south Coast of Portugal). Clams and mussels were sampled from sites close to each other to determine interspecific responses to similar environmental conditions, considering also seasonal and gender differences. Coupled with genotoxic effect, another damage biomarker (lipid peroxidation) was analysed to verify if the conditions that instigate DNA damage can be related with injury to cell membranes. For both species, DNA damage was low, reflecting the low levels of genotoxic contaminants in the lagoon, and no interspecific differences were found. However, seasonal differences were established for both bivalve species, reflecting higher environmental stress in summer. Regarding gender susceptibility, only clams showed differences in percentage of Tail DNA, with females more sensitive to DNA damage than males. Additionally, results for clams point out that factors responsible for LPO may not be the same as those causing genotoxicity. This study demonstrated that DNA damage is a sensitive biomarker to discriminate spatial, temporal and gender differences, being an appropriate biomarker for genotoxicity evaluation even in places of low contamination, such as the Ria Formosa lagoon.     

孔隙介质的渗透特性初探

孔隙的存在是岩土类介质材料结构的本质特征,它不但改变了岩土体的力学特性,而且严重影响着岩土体的渗透特性。大多数经典的渗流理论中,多孔介质模型都假定孔隙率和渗透系数是与时间无关的材料常数。实际上由于淘涮、侵蚀、冲刷等原因,它们是随时间和坐标变化的,同时又与孔隙中的压力、流速等因素有关。基于孔隙率和损伤变量之间的定量关系,从连续损伤力学的角度对多孔介质岩土材料的渗流力学特性进行了研究。首先,对传统的达西定律形式进行修正,提出了孔隙介质完备有效的达西定律（模型）;然后,对该模型中渗透参数的特性进行了讨论和分析,得出了一些有益的结论。     

2008年春季中国南方冰雪冻害林木物理折损典型样带分析

2008年春季我国南方发生了特大冰雪灾害,林木损害严重。选择江西省井冈山-吉泰盆地-于山山脉-武夷山支脉样带作为研究区,两次进行野外调查,结合收集的数据,进行综合分析,取得结论包括：（1）在研究样带内人工林的损毁程度为湿地松林〉马尾松林〉混交人工林〉杉木林,在受损样本中湿地松林的实际受损比例高达61．3％,其中不可自然恢复折损实际比例达43．2％,相对比例达70．4％,主要是因为湿地松是美国南部地区外来引进种,生长块、材质疏松,而且割脂活动较强;马尾松为乡土造林先锋树种,材质较为坚硬,但受割脂活动影响,在受损样本中实际受损受损比例也高达52．5％,其中不可自然恢复折损实际比例达31．8％,相对比例达60．9％;杉木是本地树种,实际受损比例46％,其中不可自然恢复受损实际仅14．9％,相对比例也仅32．5％,低于混交人工林。（2）调查样带自西向东,西部井冈山地区常绿阔叶林受损程度最轻,分布在700m左右的人工柳杉林受损严重,杉木林分布在700m以下的受损程度较轻,而分布在900m以上的则相对严重;中部吉泰盆地受损调查样点中,分布在低海拔的湿地松林和马尾松林,因割脂活动受损程度严重,杉木林受损最轻,长期封育的天然次生林落叶阔叶林,由于藤本植物的缠绕,导致大量冰挂积雪,受损十分严重;东部兴国和宁都县,分布在400m以下的人工飞播马尾松因个体小基本未受损,分布在400m以上的1960年代人工种植马尾松,因割脂活动,受损严重;而分布在500～900m的杉木林受损程度较轻。