混凝土坝横缝接触问题的变分不等式解法

采用建立多子结构系统摩擦接触问题的变分不等式理论，导出了相应的数值解法，并应用于三峡大坝泄洪坝段横缝接触问题的研究，分析论证了横缝灌浆前后大坝孔口应力的变化特征及不同灌浆效果对深孔孔口应力的影响，得到了一些有益的结论。     

丹江口大坝加高深孔应力研究

为满足南水北调中线方案蓄水调水要求,作为水源的丹江口水库,其大坝坝顶由原高程162.0 m加高到高程176.6 m,大坝加高后将会对深孔的底板和顶板的坝轴向应力带来影响,通过对丹江口大坝深孔坝段进行三维有限元计算,分析加高部分自重、上游水位、横缝灌浆、部分底板凿空、施工期水位等因素作用对深孔底板及顶板坝轴向应力的影响程度.分析结果表明,大坝加高会增加深孔坝轴向的拉应力,这个应力随上游水位的下降而增大;横缝灌浆对减小因大坝加高而增加的深孔坝轴向拉应力有好处;底孔凿空0.5 m,其表面应力与凿空前底板表面应力基本一致.     

横缝开合状态对高坝深孔结构力学行为影响

横缝开合状态对高坝深孔结构力学行为有重要影响。建立了考虑不同横缝初始间隙及其开合行为影响的高坝深孔分析模型,分别从“结构变形、开裂状态、应力分布及实际配筋受力状态”4个角度,结合实际工程,获取了横缝开合状态影响下孔口结构的力学行为特征,弥补了传统高坝深孔结构分析中因简化横缝状态而造成的设计偏差。研究表明,横缝初始间隙越大,高坝深孔结构变形、开裂、应力及钢筋受力等力学行为特征越趋于不利状态,结构受力性能明显降低,正确描述横缝开合状态是分析深孔真实力学行为乃至合理配筋的重要保障。     

横缝开合状态对高坝深孔结构力学行为影响

横缝开合状态对高坝深孔结构力学行为有重要影响。通过建立考虑不同横缝初始间隙及其开合行为影响的高坝深孔分析模型,分别从“结构变形、开裂状态、应力分布及实际配筋受力状态”四个角度,结合实际工程,获取了横缝开合状态影响下的孔口结构真实力学行为特征,弥补了传统高坝深孔结构分析中因简化横缝状态而造成的设计偏差。研究表明,横缝初始间隙越大,高坝深孔结构变形、开裂、应力及钢筋受力等力学行为特征越趋于不利状态,结构受力性能明显降低,正确描述横缝开合状态是分析深孔真实力学行为乃至合理配筋的重要保障。     

三峡大坝泄洪坝段布置与结构设计

三峡大坝泄洪坝段总长４８３ｍ，最大坝高１８３ｍ，为混凝土重力坝，共布置有３层６７个泄洪孔，其中表孔２２个，深孔２３个，导流底孔２２个，表孔，深孔为永久泄洪设备，枢纽最大泄洪能力达１０２５００ｍ＾３／ｓ。泄洪坝段３层大孔口，坝体布置，结构复杂，坝基采用了封闭抽水排水措施，以减小扬压力，大坝横缝高程１１０ｍ以下的进行接缝灌浆，以增强大坝整体性和改善孔口应力；深孔有压段采用钢板衬护，以改善孔口的抗磨蚀性     

溪洛渡拱坝泄水深孔应力分析

溪洛渡双曲拱坝坝身共布置7个表孔,8个深孔,以及10个导流底孔。其中深孔孔口尺寸为6m×6．7m,泄水水头高105m,深孔出口处闸墩最大悬臂长达24．87m,闸墩最小厚度为3．5m,支撑大梁尺寸为8．0m×7．0m×5．0m（长×宽×高）,另外出口处弧门推力巨大,单孔弧门推力最高达82857kN,其应力应变状态极为复杂。采用三维有限元法对溪洛渡拱坝建立精细整体模型,对深孔部位进行应力分析研究。分析表明：溪洛渡拱坝闸墩预应力吨位和布置合理,表现在深孔孔口应力在进口段、孔身以及出口段可以满足设计应力要求;对于工况三（正常蓄水＋温降＋弧门挡水）大坝运行时,支铰大梁和闸墩下游端部出现拉应力最大极值,拉应力分别为3．0MPa和2．6MPa,但是分布范围有限,可以通过适当配筋满足设计要求。另外,文中还与二滩拱坝中孔孔口应力进行了类比分析,结果表明溪洛渡深孔孔口应力与二滩中孔类似,孔口角缘压应力存在偏压现象,但由于溪洛渡拱坝孔口周围温降荷载小,使得溪洛渡孔口内壁拉应力极值小于二滩。     

高强抗震钢筋在小湾拱坝中的应用

依据小湾拱坝布设抗震钢筋方案、大坝伸缩横缝结构的特点和设计中对横缝抗震钢筋位置的要求,围绕抗震钢筋对大坝伸缩横缝抗震的影响展开研究,包括抗震钢筋牌号的选择、温度、埋设抗震钢筋对大坝横缝两侧附近区域的影响以及抗震钢筋在横缝两侧的配置方式、部位、数量等布设方案的研究。对设计方案中抗震钢筋对横缝张开度的作用效果进行检验,对抗震钢筋位置及在上、下游的层数等关系到小湾工程抗震措施具体实施中的重要问题分别进行了多方案分析和论证。     

孔口闸墩对溪洛渡拱坝静动应力的影响研究

采用显式有限元结合黏弹性人工边界的地震波动反应分析方法,在计入坝体横缝动态接触非线性影响基础上,对溪洛渡拱坝采用模拟孔口及闸墩结构、仅模拟孔口不模拟闸墩和孔口闸墩结构均不考虑的3种模型进行地震响应分析,研究孔口、闸墩结构和大坝的静态和静动综合应力响应。对比分析结果表明,孔口、闸墩的存在对大坝主体的静动综合应力分布规律影响不大,而孔口闸墩区域位于动态反应较大的坝体中上部,由于闸墩的悬挑及截面变化的复杂性,以及孔口对坝身的削弱作用,这一区域将出现数值较大的拉应力集中区,主要分布于上游闸墩根部和下游面深表孔之间以及顶部大梁位置,在溪洛渡拱坝深孔、表孔抗震设计中应予以重视。     

深层灌浆法处理大坝劈头缝的实践

本文就江垭水库采用深孔灌浆法处理大坝劈头缝取得成功的事例,详细阐述了深孔灌浆方案的确定、施工中灌浆孔口设备、灌浆工艺以及灌浆工程质量等内容。为类似工程的设计、施工提供了先例。     

江垭大坝劈头缝的深层灌浆处理

本文就江垭水库采用深孔灌浆法处理大坝劈头缝卑得成功的事例,详细阐述了深孔灌浆方案的确定、施工中灌浆孔口设备、灌浆工艺以及灌浆工程质量等内容,为类似工程的设计、施工提供了先例。     

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。