基于ANSYS的坝后浅埋管管道外包混凝土厚度研究

本文以某水电站为例,通过ANSYS软件对管道结构进行非线性有限元计算分析,对坝后浅埋管在内水压力作用下的管道承载能力进行研究。研究了7种计算方案的坝后浅埋管管道在内水压力作用下的承载规律,分析了不同外包混凝土厚度和不同的钢筋布置方式对管道结构受力、开裂情况和管道外包混凝土位移情况的影响。研究分析表明,坝后浅埋管外包混凝土衬砌厚度选择1.5m是合适的,而钢衬采用Q345钢,钢筋采用III钢筋能够满足安全要求。另外,钢筋布置时,内侧布置1层钢筋,外侧布置2层钢筋对限制裂缝宽度有利。     

三峡电站下游坝面钢衬钢筋混凝土管道结构设计

三峡电站压力管道设计采取下游坝面布置的钢衬钢筋混凝土地联合受力结构，大量的计算分析和仿真模型试验成果表明，这种结构具有较好的工作状态和较高的安全度。招标设计成果表明，在现有材料供应条件下，钢衬采用１６ＭｎＲ厚度２８～３６ｍｍ；钢筋选用Ⅱ级钢筋，分４～５层布置，这一方案是完全可行的，但为了减小施工难度，设计上将进一步研究采用提高钢筋材质及钢衬承载比例等措施，减少外包钢筋混凝土钢层数，提高结构的潜在安     

考虑摩擦接触特性的钢衬钢筋混凝土管道承载机理研究

采用库伦摩擦接触模型模拟钢衬与外包钢筋混凝土间摩擦接触特征,建立了李家峡水电站坝下游面钢衬钢筋混凝土管道结构模型,系统研究了内水压力作用下外包混凝土起裂荷载、裂缝扩展、管道变形、钢衬与钢筋应力分布特征等承载性能规律。结果表明:考虑钢衬与外包混凝土间的摩擦接触机制时,混凝土裂缝扩展规律与模型试验吻合更好,钢衬应力更为均匀,混凝土裂缝宽度普遍在0.3~0.4 mm,明显大于不考虑摩擦接触特性结果;随着钢衬与外包混凝土间摩擦系数的增加,管顶附近的变形不均匀程度逐渐增加,钢衬应力不均匀程度增加,不利于发挥钢衬的承载性能,但同时上半周裂缝处的钢筋应力峰值明显减小,应变不均匀程度减小,说明摩擦系数的增加有利于裂缝控制。     

对敷设在下游坝面的高水头大直径压力管道力学性能的研究

敷设在下游坝面的高水头大直径钢衬钢筋混凝土压力管道是近年来发展起来的一种新型管道布置方式及结构型式。笔者通过对李家峡水电站下游坝面压力管道的原型仿真材料结构模型试验,研究了在内水压力作用下压力管道的钢衬、钢筋、混凝土的应力状态及混凝土的弹性变形,以及管道的开裂特征和破坏机理。研究成果表明,压力管道在开裂前,钢材处于低应力状态,混凝土承担大部分内水压力;压力管的钢材、钢筋、混凝土能够可靠协调地联合作用;作为下游坝面压力管道的设计,不一定强求初裂荷载大于设计工作荷载,否则会增加材料用量;混凝土微裂纹对开裂的影响及微观机理,尚须进一步研究。     

钢衬钢筋混凝土压力管道非线性理论研究

钢衬钢筋混凝土压力管道是水电站广泛采用的新型结构,其内水压力等荷载由钢衬和外包的钢筋混凝土共同承担.结合工程应用,系统地总结了下游坝面钢衬钢筋混凝土压力管道非线性有限元分析的特点,并从混凝土本构关系模拟(采用非线性弹性模型、弹塑性模型、内时模型、断裂力学模型、流变学模型、损伤力学模型)、混凝土裂缝模拟、钢筋模拟和钢筋与混凝土之间粘结模拟等方面介绍了研究进展情况,指出了进一步研究需要解决的问题.     

三峡电站引水压力管道设计研究

三峡电站引水压力管道直径大（12．4m），条数多（26条）。为避免管道安装与大坝混凝土施工的干扰，压力管道布置采取在下游坝面预留浅槽的背管形式，管道埋入坝面以下约1／3直径。这种布置形式有利于提高管道抗震能力，缩短管道长度，减少工程量。压力管道背管部分采用钢材钢筋混凝土联合受力型式，这种管道的安全度要比明钢管高；钢衬可采用16Mn钢板，板厚在36mm以内，有利于加工焊接；钢材可立足于国内；造价要比明钢管节省。为保证钢衬钢筋混凝土管道有较大的安全度，钢衬和钢筋混凝土按各自单独承受全部内水压力时的安全系数大于1，总安全系数为2．2设计。下游坝面浅预留槽采用方圆形加小贴角的形式。浅留槽两侧直干墙段与管道之间加设软垫层。管道钢筋混凝土的厚度为2m。     

坝后背管结构力学弹性中心法的应用

简要介绍了坝后背管结构力学弹性中心法，并利用结构力学弹性中心法对国内外已建坝后背管工程和地面外包混凝土钢管工程进行结构分析和配筋优化。分析发现，坝后背管外包混凝土的外圈钢筋应力大于内圈钢筋应力和钢管应力，外包混凝土厚度设计基本合理，但在钢筋布置上值得进一步优化。结构力学弹性中心法计算结果可靠，方法简便。     

有限单元法和弹性中心法在坝后背管结构设计中的应用比较

结合三峡水电站工程实际,采用有限元软件ABAQUS对坝后背管结构进行了平面非线性有限元计算,并将结果与模型试验、结构力学弹性中心法成果比较,研究了结构力学弹性中心法在坝后背管设计中的适用性。研究结果表明,有限元方法能更好地反映管道结构裂缝开展、钢衬和钢筋应力分布规律,而结构力学弹性中心法计算得到的外圈钢筋应力偏大,不仅难适用于全背式背管,对浅槽式背管的计算误差更大。浅槽式背管由于两侧坝体混凝土对管道的约束作用,不仅可提高初裂荷载,减小裂缝处钢衬和钢筋应力和裂缝宽度,而且与全背式背管相比对管道抗震更有利。     

坝后背管外包混凝土厚度研究

采用平面非线性有限元法对某水电站下游面钢衬钢筋混凝土压力管道进行了分析,计算中考虑混凝土开裂和地震作用的影响。研究了5种外包混凝土厚度0.5、0.8、1.2、1.5和2.0m的坝后背管在内水压力和地震作用下的承载规律,分析了外包混凝土厚度对管道的动、静力承载性能的影响。结果表明,设计内水压力作用下,外包混凝土厚度较小时,管坝接缝面附近的局部坝体开裂,并使管道钢材应力提高,但其材料强度和变形仍能满足规范要求。地震作用分析表明,外包混凝土越厚,坝后背管结构的基频值越高;但厚度越大,管道钢材动应力值也越大,说明采用较小的外包混凝土厚度有利于减小钢材的动应力。因此,在满足施工要求和安全的前提下,建议在坝后背管设计中采用厚度较薄的外包混凝土。     

里底水电站厂房肘管二期混凝土施工技术

里底电站厂房尾水肘管带有内钢衬,钢衬加劲环把肘管分成多个区,且肘管锚筋较密,又布置有独立支墩,施工空间狭小。厂房尾水肘管钢筋布置密集,钢筋绑扎量大。肘管底部面积大,且要保证肘管钢衬底部混凝土的密实,对混凝土级配、和易性,间隙通过性等要求较高。厂房尾水肘管钢衬的安装精度高,施工过程中必须严格控制混凝土的入仓速度。为保证浇筑密实,因此厂房肘管二期混凝土施工采用一级配高流态自密实混凝土浇筑[1]。     

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。