强潮作用下钱塘江河口潮余流特征研究

钱塘江河口是典型的强潮河口,研究其潮余流特征对于深入了解强潮特性及潮汐资源开发利用具有重要意义。采用钱塘江河口枯季大潮期沿程5个站点连续5 d高频次的流速、潮位、水深等观测数据,分析了强潮作用下潮流、水深及余流的时空变化特征,讨论了余流与水深、潮差的关系。结果表明:在强潮作用下,河口下游段水流向陆净输运,余流主要受斯托克斯余流控制;上游段水流向海净输运,余流主要受欧拉余流控制。大潮期前期阶段,向陆输运的余流促使河口段出现蓄潮现象,水深持续增加,后期阶段余流与潮差具有极强的相关性。     

钱塘江饮用水源地含氯度受潮汐与径流影响分析

钱塘江河口段受潮汐和上游径流的作用,水体含氯度变化较大,对沿江工农业、生活取水产生了较大影响。依据钱塘江河口段七堡站9个月实时监测的水体含氯度数据,分析了潮汐和径流对饮用水源地含氯度变化的影响。结果表明,随着潮汐作用的减弱,七堡站咸水入侵的强度、含氯度日超标时间等均逐渐减小;上游径流量的增大,可有效降低饮用水源地的含氯度,但随着径流量的增加,径流的抑咸作用越来越小,当径流量超过一定值后,继续增加流量对氯度的稀释作用已非常微弱。依据分析结果,参照国家规定的饮用水含氯度标准,确定了大、中、小潮期间,水体含氯度符合标准的时间,以及上游抑咸的最佳下泄流量。     

钱塘江河口七堡段氯度时空变化及与水文的关系

对10多年钱塘江河口七堡段大量的氯度、水文、地形等实测资料进行了统计、分析和比较,结果表明:在径流、潮流此消彼长的影响下,河口闸口—仓前河段咸淡水掺混最为强烈,径流大则氯度低,潮汐强则氯度高,但氯度垂向分布比较均匀,横向差异小,主槽氯度大于边滩;连续丰水年、连续枯水年,盐水入侵均较弱,径流从丰转枯的第一年,盐水入侵较强;大潮期受潮波变形和涌潮等影响,涨潮动力显著大于落潮,易发生盐水入侵;潮差是潮动力的重要指标,潮动力决定盐水入侵强度,潮差对河口的盐水入侵具有重要的指示作用。     

磨刀门日潮平均盐度变化及驱动力分析

基于日潮平均的盐量输运方程,利用变量分离的方法分析实测资料,对磨刀门河口大小潮变化过程中引起日潮平均盐通量变化的驱动力进行了研究。结果显示磨刀门日潮平均盐度变化主要由平流输运和重力环流输运驱动,说明磨刀门河口是一个非稳态河口。大小潮变化过程中,从大潮转小潮的中潮阶段到下一个周期小潮转大潮的中潮阶段,重力环流作用大于平流输运作用,盐量在河口持续增加,各站点盐度持续增大;在小潮转大潮的中潮阶段到大潮转小潮的中潮阶段,平流输运作用大于重力环流作用,盐量在河口持续减少。咸潮上溯过程中,下游站点的纵向盐度梯度先于上游增大,也先于上游减小,上游站点盐度从增大变为减小的时间比下游站点有所滞后。     

径流-潮汐相互作用与咸潮上溯距离试验研究

河口动力机制复杂,生态环境敏感脆弱,珠江三角洲咸潮上溯距离逐年上移,对生态环境造成了巨大的影响。咸潮上溯距离受径流和潮汐影响显著。该文采用物理模型试验方法,对径流和潮汐共同作用下的咸潮上溯距离进行分析,结果表明:1)增加上游径流量,引起河道水力坡度变陡使得咸界整体往下移动;2)存在临界潮差,使咸潮涨憩时上溯距离最小;3)上游同样增加相同径流量时,潮差小时咸界下移距离大于潮差大时的咸界下移。最后利用Fischer的分层-环流图阐述了产生其偏差的机理:一方面当潮差小时,引起的分层系数变化和/s fu u变化幅值更大;另一方面,增加径流量时改变了密度环流输运作用,而潮差较小时密度环流输运是主导因素,此时增大的径流量,改变了主导因素的输运比例,引起了较大的作用效果,反之,潮差大时作用效果则较小。     

非恒定水域盐水入侵特性试验研究

通过10组试验研究了非恒定水域盐水入侵特性与上游淡水来流、水深、潮差、下游盐度等参数之间的关系。结果表明:①表层和底层的盐度几乎不受涨落潮的影响,表层盐度一直较低,底层盐度一直较高;中间层的盐度具有周期性,且一般在涨憩时刻附近取得最大值,落憩时刻附近取得最小值。②下游盐度、水深以及潮差越大,上游来流越小,盐水入侵强度越大。垂向平均盐度值在纵向上从下游向上游递减。总体来讲,下游纵向盐度梯度比上游的大,且纵向盐度梯度在中游附近达到最大。③上、中、下游断面盐度垂向分布明显不同,下游表层盐度梯度较大,且下游盐度、潮差、上游来流、水深越大,下游表层垂向盐度梯度越大。总体来说,表层垂向盐度梯度从下游向上游递减,而底层垂向盐度梯度从下游向上游递增。④从下游至上游,表层盐度值基本没有变化,底层盐度减小但减小速率较慢,中间层盐度值减小速率较快。     

西江河口咸潮入侵的输运机理研究

近年来,西江河口地区咸潮入侵的问题越发严峻,严重威胁人民的日常生活,故对河口咸潮咸水物质输运转移变化机理研究尤为重要。采用水动力学方法进行河道盐度的扩散演算,构建河网水质的数学模拟模型。在建模的基础上,用其模拟西江河口水流、盐度输运变化规律,并与实测水文资料进行对比。结果说明,模拟计算曲线与实测曲线相对一致,该模型具有适用性。该模型可用来预报西江河口咸潮入侵的影响时间、影响范围,数值模拟咸潮上溯的环境影响,进而提出应对和控制咸潮上溯的对策措施,实现对未来咸潮入侵过程的模拟,为河口咸潮入侵的预报与防治工作提供丰富的资料和可靠的技术支持。     

珠江三角洲咸潮活动规律研究

通过对大量实测水文、地形和含氯度等基础资料的分析，了解珠江三角洲及其河口地形变化及含氯度变化规律，并通过数学模型分析不同来流、地形变化及三角洲分流变化对珠江三角洲咸潮入侵的影响。研究成果为澳门珠海供水保障规划提供参考数据。     

珠江三角洲咸潮活动规律研究

通过对大量实测水文、地形和含氯度等基础资料的分析,了解珠江三角洲及其河口地形变化及含氯度变化规律,并通过数学模型分析不同来流、地形变化及三角洲分流变化对珠江三角洲咸潮入侵的影响。研究成果为澳门珠海供水保障规划提供参考数据。     

杭州湾年最大潮差分析

潮差变化对水沙输移、潮滩演变、涌潮、盐水入侵、潮能开发、港口航运、水产养殖和生态环境均有较大影响.该文基于杭州湾实测潮汐资料,对杭州湾年最大潮差时空变化、成因及增大原因进行了系统分析.结果表明:钱塘江河口最大潮差位置位于澉浦上游;年最大潮差杭州湾北岸出现在8月的次数最多,杭州湾口南岸镇海出现在12月和1月的次数最多;所...     

地下厂房施工过程的三维非线性数值模拟分析

根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。     

Evaluation of freshwater mussel relocation as a conservation and management strategy

The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

基于BP神经网络-马尔科夫链模型的隧道围岩位移预测

在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。     

Short communication. Pipelines as a refuge for freshwater snails

In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment.     

浙江省水域调查录入系统的设计和应用

浙江省水域调查录入系统将调查数据与电子地图相整合,对分类水域数据进行统计计算,并对输入数据进行合理性和完整性检查,得到调查范围内现有水域的详细数据,实现了水域调查数据输入、计算、统计和查询的数字化管理,提高了工作效率和工作质量,为各地下阶段水域保护规划编制和水域管理工作提供了数据支持。对该系统的设计原则、功能和技术设计等作了介绍。     

基于CT-连续加荷水泥乳化沥青混凝土细观损伤规律研究

利用CT技术对水泥乳化沥青混凝土的细观损伤过程进行实时扫描观测,获得了混凝土试件在连续加荷下的CT图像。通过采用直观分析法、CT数分析法、CT数与损伤变量关系3种方法分析表明,水泥乳化沥青混凝土的破坏过程可分为压密、扩容、裂纹扩展、破坏4个阶段,同时混凝土在受压过程中具有韧性,在极限荷载之前各断面处于压密和微扩容的强化阶段,极限荷载之后混凝土从损伤到破坏发展比较平稳。     

浅谈天湖水电站水轮机运行故障及处理措施

简述天湖水电站投运以来各种故障的表现形式，分析其原因，提出了相应的处理方法及措施，并对合理利用国内外设备提出建议。     

Fish assemblage response to recent mitigation of a channelized warmwater stream

Various designs of low‐head dams are used to rehabilitate streams or forestall upstream channel incision after channelization. We report on the efficacy of using notched sills and grade control structures (GCS) to restore the fish assemblage in Luxapallila Creek, Mississippi. We tested the null hypotheses that habitat variables and species richness, evenness, and assemblage structure would not differ among: (1) a channelized segment with no modifications; (2) a channelized segment mitigated by the installation of sills and GCS; (3) a segment upstream of the installations and undergoing channel incision; and (4) an unaltered segment. Although habitat variables changed, neither species richness, evenness, nor fish assemblage structure differed between mitigated and channelized segments with both exhibiting less richness and different assemblage structures than the unaltered segment. Lack of differences in species richness between the incised and unaltered segments suggest that the GCS may have halted the negative effects of upstream channel incision before species were extirpated. Conspicuous habitat differences between the altered (channelized and mitigated) and unaltered segments were lack of backwaters and canopy coverage and finer substrates in the altered segments. Our results suggest a more comprehensive rehabilitation strategy is required in Luxapallila Creek. Published in 2003 by John Wiley & Sons, Ltd.     

NUMERICAL STUDY OF WAVE EFFECTS ON SURFACE WIND STRESS AND SURFACE MIXING LENGTH BY THREE-DIMENSIONAL CIRCULATION MODELING

1. INTRODUCTION Coastal and continental shelf regions are characterized by intensive interaction between wave and current. These regions are of great economic significance to mankind. Therefore, the modeling of wave and current as well as their mutual int…