三峡工程的大江截流与二期围堰

三峡工程大江截流采用“上游单戗立堵、双向进占、下游尾随、预平抛垫底”施工方案。截流设计流量为１４０００－１９４００ｍ＾３／ｓ，最大落差１．２４ｍ，最大流速３．７ｍ／ｓ。大江截流及二期围堰的特点是工程最大、工期短、施工强度大、流量大、水深大、库容大，以及围堰基础地质复杂等；关键技术问题是堤头坍塌和堰体稳定、堰基新淤沙稳定以及复杂地质条件和人工填料条件下的防渗墙施工问题。     

三峡工程的大江截流及二期围堰

三峡工程施工导流采用“三期导流,明渠通航”方案。大江截流采用“上游单戗立堵、双向进占、下游尾随、预平抛垫底”施工方案。截流设计流量为１４０００～１９４００ｍ３／ｓ,最大落差１２４ｍ,最大流速３７ｍ／ｓ,优选合龙时段在１９９７年１１月中旬。大江截流及二期围堰的特点是工程量大、工期短、强度大,流量大、水深大、库容大,以及围堰基础地质复杂等;关键技术问题是堤头坍塌和堰体稳定、堰基新淤砂稳定以及复杂地质条件和填料条件下的防渗墙施工问题     

三峡工程的大江截流及二期围堰

三峡工程施工导流采用“三期导流,明渠通航”方案。大江截流采用“上游单戗立堵、双向进占、下游尾随、预平抛垫底”施工方案。截流设计流量为14000～19 400 m~3/s,最大落差 1.24 m,最大流速3.7 m/s,优选合龙时段在 1997年11月中旬,实际已在 11月 8日胜利合龙。大江截流及二期围堰的特点是工程量大,工期短,强度大,流量大,水深大,库容大,以及围堰基础地质复杂等;关键技术问题是堤头坍塌和堰体稳定、堰基新淤砂稳定以及复杂地质条件和填料条件下的防渗墙施工问题。     

三峡工程大江截流水文测验设计

三峡工程大江截流，是实现拦断长江主河槽，形成二期围堰，为大江主体工程创造干地施工条件的关键工程。它具有水深大，流量大和抛投量大，截流过程中水流泥沙条件和地形变化复杂等特点。为指挥截流平抛垫底，围峡工程坝区河段开展水位，流速，流量，泥沙，水面动态，水下地形及河床冲淤等项目观测，提供高质量的水文原型观测资料和成果。     

三峡工程围堰施工技术问题的突破

介绍三峡工程施工导流的“三期导流 ,明渠通航”方案 ,对一期土石围堰施工技术 ,混凝土纵向围堰施工技术 ,大江截流与二期土石围堰施工技术 ,三期围堰施工技术以及所涉及的重大技术突破进行介绍 ,着重阐述大江截流方案 ,大江截流上下游土石围堰平抛垫底及二期围堰防渗等关键技术 .     

三峡工程主要科技成果及应用

介绍三峡工程的科研项目，综述三峡工程开工以来的主要科研成果及工程应用情况，包括”：一期土石围堰基础处理与施工技术；大江截流上下游土石围堰平抛垫底研究；二期参工程     

三峡工程二期围堰施工实践

三峡工程二期围堰是二期导流期间重要的挡水建筑物。二期围堰工程施工历经平抛垫底、大江截流、风化砂振冲加密、防渗施工、围堰加高渡汛等关键步骤,解决了许多施工技术难题。围堰建成后,经受了长江洪水的考验,其变形监测和渗漏观测成果均控制在设计范围内。二期围堰工程施工质量优良。     

三峡工程大江截流及二期围堰施工难点分析

三峡工程大江截流及二期围堰的施工难眯在于截流时抛填埋 稳定及连续高强度抛投历时长，堰基淤沙对本稳定的潜在威胁及围堰参体的施工。     

二期横向围堰工程的几个主要技术问题

二期围堰是三峡工程施工的屏障。围堰工程总量大、工期短、强度大、施工难度大，基础地质条件复杂。在长期研究和大量现场施工试验的基础上，妥善地解决了基础新淤砂和强透水岩体处理、深水抛填、风化砂堰体和深混凝土防渗墙设计和施工中的关键技术问题，确保了深水围堰的按期建成和安全运行。     

大江截流及二期围堰工程进度控制分析

大江截流及二期围堰工程项目是三峡工程总进度计划网络中的关键项目。工期紧，任务重，地质、地形条件极为复杂，技术难度极大。确保施工质量条件下的进度控制，是二期围堰工程建设的重要课题。实施中通过工序优化，提高工艺等，较好地达到进度控制的目的。     

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。     

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.     

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。