堤防工程失事概率分析方法及溃决模式研究

根据从控制洪水向洪水管理转变的技术要求,简述了在洪水风险分析中开展堤防工程失事概率分析和溃决模式研究的必要性。讨论了堤防漫顶概率、溃堤概率和堤防溃口发展过程模型等方面的一些分析方法、经验关系和经验数据。建议尽快出台适合我国国情的堤防工程安全管理技术导则,提出实用的堤防工程可靠性计算方法,开发堤防溃决过程模型。     

截渗墙与放淤固堤技术在堤防加固中的比较

目前黄河下游堤防加固的主要工程措施是截渗墙与放淤固堤技术,通过对这两种技术在黄河下游堤防加固中的情况进行对比,指出放淤固堤技术仍是今后黄河下游加固堤防的首选措施。     

黄河下游堤防工程的安全性综合评价

紧密结合黄河下游堤防工程的实际情况,建立了黄河下游堤防工程安全性综合评价的指标体系,根据建立的判断矩阵,应用基于加速遗传的层次分析法确定各个评价指标的权重;其次,根据专家评分法得到各项基础指标的评价值;最后,利用所得指标评价值和指标权重对黄河下游堤防工程的安全性进行综合评价,结果表明:该方法计算简捷、计算精度高。     

从“96.8”洪水谈黄河下游堤防建设

本文从黄河下游堤防工程现状和黄河下游“９６．８”洪水出发，分析了黄河大堤存在的问题和目前的防洪形势，认为目前大堤的高度基本满足的防洪要求，堤防漫决的可能性较小，堤防建设的主要任务是进行堤身加固。在分析各种堤防加固措施的作用后，得出机淤固堤是一种综合性的加固措施，对提高堤防的抗洪强度具有显著效果。     

黄河河南段标准化堤防规划与建设

标准化堤防建设是把黄河下游防洪工程由分散建设改为集中建设的一种新的建设思路。黄河河南段目前仍面临着严峻的防洪形势，并存在堤身隐患多、河道整治工程不完善、生物防洪工程规模小、堤防管护设施严重不足等问题，迫切要求进行标准化堤防建设。黄河河南段标准化堤防建设的主要内容包括：堤防加固工程、险工改建工程、堤顶道路及防汛抢险道路工程、堤防管护设施、生物防护工程等。     

真空预压法用于黄河标准化堤防建设的可行性

分析了黄河下游堤防存在的主要问题,介绍了标准化堤防体系,阐述了真空预压法处理软土地基的原理、设计要求、施工方法及质量检验的主要内容,认为真空预压技术可在黄河下游标准化堤防建设中推广。     

70年来黄河下游历次大修堤回顾

堤防是最主要的防洪工程,黄河下游堤防在1946—1949年初期进行复堤建设的基础上,分别于1950—1957年、1962—1965年、1974—1985年、1996—2018年进行了4次大修堤。通过简述历次黄河下游大修堤的目标、标准、施工情况、工程量等,系统总结了70 a来黄河下游堤防建设的成就,并指出做好工程管理是堤防发挥作用的前提,同时还应加强其他防洪工程建设和防汛工作。     

超标洪水下堤防失事风险评价及工程应用

基于堤防工程可能的失效模式,修正了水文失事风险率和边坡滑动失稳风险率计算模型.分析了漫顶失事、渗透破坏失事以及边坡滑动失稳的条件概率计算方法,建立了堤防综合失事风险率计算模型;同时,提出了超标洪水下堤防失事风险率的计算方法,结合南京市外秦淮河堤防工程实例,得到超标洪水下外秦淮河堤防综合失事风险率为0.57%.     

溃堤洪水的二维水动力模型及其应用

为了减少堤防溃决造成重大的生命财产损失,加强防洪减灾非工程措施建设,建立了溃堤洪水的二维水动力模型,对溃堤洪水的精细化仿真模拟。该模型考虑了溃堤口门展宽变化,局部网格加密处理,并采用干湿水深理论与热启动技术对模型进行优化。将该模型应用于黄河内蒙段南岸灌区的溃堤洪水演进模拟,利用2008年杭锦旗奎素段实际溃堤数据对所建模型进行验证,结果表明:流场分布均匀且光滑,计算结果合理可靠,模型具有较高的计算精度及可靠性。采用该模型模拟了沙圪堵工程与奎素段堤防同时溃决的情形,并绘制了洪水风险图,为该地区防洪风险管理决策提供了重要的技术支持。     

防洪堤工程系统可靠度分析

运用串并联系统的可靠度理论,将堤防工程系统分为整体稳定子系统、渗透变形子系统、沉降变形子系统.采用界限估计法计算堤防的各主要失事模式的失事概率,在此基础上进行综合评估得到防洪体系的系统失事率.结合杭州市钱塘江南岸南沙支堤工程实例,得出工程段的界限组合失稳概率为0.15%,为堤防工程的优化设计提供了一种思路.     

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。     

Serial discontinuities in a Rocky mountain river. I. Distribution and abundance of plecoptera

Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m^?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m^?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m^?2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m^?2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m^?2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river.     

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。     

Automated system for removal and pneumatic transport of fly ash from electric precipitator hoppers

A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system, configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants of dry ash utilization and the advantages of producing of size-separated particles are considered. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).     

The flood pulse advantage and the restoration of river-floodplain systems

The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed.     

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。