Damage investigation of girder bridges under the Wenchuan earthquake and corresponding seismic design recommendations

An investigation of girder bridges on National Highway 213 and the Doujiangyan-Wenchuan expressway after the Wenchuan earthquake showed that typical types of damage included： span collapses due to unseating at expansion joints; shear key failure; and damage of the expansion joint due to the slide-induced large relative displacement between the bottom of the girder and the top of the laminated-rubber bearing. This slide, however, can actually act as a form of isolation for the substructure, and as a result, the piers and foundation of most of the bridges on state route 213 suffered minor damage. The exception was the Baihua Bridge, which suffered severe damage. Corresponding seismic design recommendations are presented based on this investigation.     

景洪市嘎栋地热井特征及成井工艺总结分析

景洪盆地内蕴藏有丰富的地热资源。通过对景洪市嘎栋地热资源勘查地热井地质、施工情况及成果进行介绍,结合勘查施工实践,针对地热资源勘查开发、地热钻井施工、成井工艺及钻井过程中地质问题等有关内容进行经验总结并分析,对地热地质条件与地热井施工之间结合进行一些经验探讨,并对现行地热井规范中关于井身结构设计、取水层位确定、单井资源量计算等问题提出一定疑问。旨在通过实践及疑问探讨,力图找出为地热资源勘查开发提供值得借鉴的经验和教训。     

柴达木盆地西部新生界陆相湖盆碳酸盐岩沉积环境与沉积模式*

利用野外露头、岩心、测井录井和分析化验资料,对柴达木盆地西部(简称“柴西地区”)新生界干柴沟组湖相碳酸盐岩进行了研究,划分了其沉积微相类型,研究了其分布规律,分析其形成环境和控制因素,并建立了相应沉积模式。该区湖相碳酸盐岩在垂向上与碎屑岩频繁互层,湖相碳酸盐岩包括颗粒灰岩、藻灰岩、泥晶灰岩和混积岩4大类11种,划分出了灰泥坪、颗粒滩、藻丘(礁)、浅湖湾以及(半)深湖泥灰岩相等5种沉积微相。通过分析不同碳酸盐岩及其微相时空展布特征,认为其发育主要受控于湖盆构造运动、湖平面变化、陆源碎屑注入、古气候与古水介质条件、古地貌与古水深环境,并在此基础上建立了柴西湖相碳酸盐岩的沉积模式。研究认为柴达木盆地西部干柴沟组沉积时期,湖盆为典型咸化湖盆,构造活动相对稳定,湖平面上升达到峰值。碳酸盐岩主要发育在湖侵期,高频湖平面变化形成了碳酸盐岩与碎屑岩频繁互层。在枯水期,盆地坡折处发育碎屑岩滩坝或三角洲前缘沉积;在湖侵期,盆地坡折处发育了鲕粒滩及藻灰岩,盆地洼陷区发育泥灰岩或灰质泥岩。     

表层土剪切波速的不确定性对地表设计谱平台值的影响

土层剪切波速对地表反应谱有重要的影响。选取构建了不同场地类别的235个场地地震反应模型,人工合成了12条强弱及频谱特性不同的加速度时程,运用一维土层地震反应的等效线性化波动方法,研究了不同地震动输入下表层土剪切波速的不确定性对设计谱平台值的影响,统计给出了表层土剪切波速的变异率与地表设计反应谱平台值间的经验公式。结果表明:地表设计反应谱平台值与表层土剪切波速的变异率呈负相关关系,即随表层土剪切波速变异率的增大而减小;不同地震波输入条件下各类场地类别地表设计谱平台高度与表层土剪切波速变异率的数学模型为一阶指数函数。     

近25年营口浮渡河口湿地景观格局演变过程及驱动因素分析

文章通过提取1992年、2007年、2017年三期春季大潮营口浮渡河口遥感影像景观图斑,总结了近25年营口浮渡河口湿地景观格局演变过程,分析了演变的驱动因素。25年间,受人类活动的影响,浮渡河口湿地景观格局出现破碎化现象,系统形成机制遭到破坏,造成河口沙坝-潟湖景观割裂和缩减,湿地生态系统已受到严重影响。对此,文章建议在深入理解浮渡河口湿地景观形成机制、规律及驱动因素的基础上,采取“源头管控”“河岸加固”“构筑物清理”的修复治理措施以恢复其形成机制,使河口湿地生态系统得到修复。     

杭州市区春节期间空气质量变化特点

分析近3年春节期间的空气质量资料，结果表明，杭州市区环境空气中PM10、SO2、NO2浓度较高，烟花爆竹燃放期间3种污染物出现高峰值，这与烟花爆竹燃放有关，PM25／PM10的比值高于年均值。     

基于形态学和DNA条形码探讨“南鲳”物种有效性

众所周知鲳科鱼类均为重要的经济种类,在中国沿海仅见鲳属(Pampus)鱼类分布,而低鳍鲳属(Peprilus)和真鲳属(Stromateus)则分布于大西洋和东太平洋。本研究采用形态学和DNA条形码技术对海南、广西和广东水产品市场上出现的“南鲳”进行物种鉴定,同时下载该物种的COⅠ基因同源序列进行比较分析,并纠正GenBank中的错误序列。研究结果显示“南鲳”学名实为中间低鳍鲳(Peprilus medius),为冰冻进口货品,在我国沿海无该物种的分布报道,其与国内已知的6种鲳属鱼类在鳃耙、背鳍、臀鳍等外部形态上存在明显的差异,在COⅠ基因水平上与鲳属鱼类遗传距离为0.138,分化于中新世晚期。本研究可为水产品市场种类鉴定提供借鉴,也为鲳科鱼类的研究和海洋鱼类分类学提供基础数据和参考。     

Optimal and sustainable extraction of groundwater in coastal aquifers

Four examples are investigated for the optimal and sustainable extraction of groundwater from a coastal aquifer under the threat of seawater intrusion. The objectives and constraints of these management scenarios include maximizing the total volume of water pumped, maximizing the profit of selling water, minimizing the operational and water treatment costs, minimizing the salt concentration of the pumped water, and controlling the drawdown limits. The physical model is based on the density-dependent advective-dispersive solute transport model. Genetic algorithm is used as the optimization tool. The models are tested on a hypothetical confined aquifer with four pumping wells located at various depths. These solutions establish the feasibility of simulating various management scenarios under complex three-dimensional flow and transport processes in coastal aquifers for the optimal and sustainable use of groundwater.     

原华北地台早前寒武纪演化的巨旋回

导言原华北地台分布于东经105°以东,北纬30°—40°之间。东南部中、晚元古范围比黄汲清中朝准地台向南延伸稍远,包括淮阳地区以南部分在内(图1)。五十年代开始区域地质调查,七十年代早期在野外认识基础上,作了区域性归纳(程等,1973,1982a,1982b),此外,对矿物相、变质相系、混合岩、花岗岩(程、张,1982;董申保,1982),矿物对的地温地压(张,1981:靳是琴等;1982),氧同位素研究(崔等,1980)。为进一步     

8.4 ka以来纳木错湖芯介形类组合的环境变化意义

A 332-cm long lacustrine core was drilled in the Nam Co in the central-southern part of the Tibetan Plateau. From the core, 15 species of ostracods (Crustacea: Ostracoda), which belong to 6 genera have been identified. According to the variations of the ostracod assem-blages and the ostracods ecological features, which are sensitive to the changing environ-ment, three main stages can be distinguished as follows: Stage I was from 8400 to 6800 a BP, during which the climate was cold-humid, and the lake depth changed from shallow to deep. Stage II was from 6400 to 2500 a BP, during which the climate changed from warm-humid to cold-humid, and then to cold-dry. The lake depth gradually became deep. The shifting of cli-mate, from wet-cold to dry-cold during this period, had constructed the basis of present en-vironment in the Nam Co. Stage III was from 2500 a BP to the present, which showed a trait of lake depth increasing. At the earlier period of this stage, the climate kept as cold-dry as that in the former stage, but the salinity of the lake increased. At the later period of this stage, the degree of cold-dry was enhanced, and the activities of land surface runoff tended to be weakened. Our research also found that the peak values of ostracods with black shell was coherent with the maximum production of the ostracods, and agreed with the increasing sedimentary water dynamics. This indicated that the ostracods with black shell was simulta-neous with the high prolificacy of ostracod, and transported from other places. The abun-dance of Candona juvenile shells reflected the high mortality of that kind of ostracods under an unfavorable condition. This was probably a result of the rapid change of water dynamics of sedimentary environment.