护岸式铅丝笼丁坝挑角的选择

通过室内模型试验,研究了不同挑角时丁坝附近的水流结构、坝后回流区及自由水面的变化情况,以及不同挑角丁坝附近局部冲淤变化的规律。结果表明:随着丁坝挑角的增大,坝上游流速减小区范围扩大,坝头流速变幅增大,坝后回流区长度和宽度均有所增大,坝头水面比降也增大;结合实际工程经验,建议护岸式铅丝笼丁坝的挑角宜设计为下挑45°。     

桩式抛右丁坝技术在滦河西庄险段的应用

桩式抛石丁坝是一种导流护岸工程措施,由预制混凝土桩,铅丝笼块石及柴排构成,它具有基础深,抗冲能力强,结构稳定,施工方便,节省投资等优点,弥补了传统铅丝笼抛石坝易折断毁的缺陷.在规划布置时,宜布置成下挑式,顺水导流;施工时采用射水沉桩的方式固定混凝土桩,人工在混凝土桩间填置铅丝笼块石.此技术经在滦河左岸昌黎县西庄险段初步试用,取得成功,值得进一步研究推广.     

桩式抛石丁坝技术在滦河西庄险段的应用

桩式抛石丁坝是一种导流护岸工程措施，由预制混凝土桩，铅丝笼块石及柴排构成，它具有基础深，抗冲能力强，结构稳定，施工方便，节省投资等优点，弥补了传统铅丝笼抛石坝易折断毁的缺陷。在规划布置时，宜布置成下挑式，顺水导流；施工时采用射水沉桩的方式固定混凝土桩，人工在混凝土桩问填置铅丝笼块石。此技术经在滦河左岸昌黎县西庄险段初步试用，取得成功，值得进一步研究推广。     

卵漂石铅丝笼在西藏水土流失治理工程中的应用

卵漂石铅丝石笼具有经济、简易、透水、柔性、美观等特点,现广泛应用于西藏水土流失治理项目中的拦挡、护岸、沟床固定等工程。应用结果表明:卵漂石铅丝笼用于西藏各行业开发建设项目的挡土墙、挡渣墙时,当拦挡高度h≤1.5 m时,可直接采用矩形、梯形、直角梯形断面;当拦挡高度1.5 mh5 m时,采用台阶矩形断面。卵漂石铅丝笼用于坝式护岸护滩工程时,断面多采用台阶梯形和梯形,基础埋深根据冲刷深度确定,若冲深1.0 m,将基础埋深控制在1.0 m以内,0.5 m左右为宜。在顺直段、地基好、不宜受淘刷的河段,顺坝长度可根据铅丝笼每卷长度分段;在河流弯道和易发生不均匀沉降、易淘刷部位以8~15 m为宜。实践证明:卵漂石铅丝笼顺坝、丁坝具有良好的抗变形适应性和抗冲刷性,即使在山洪作用下基础被淘空导致整体垮塌的情况下仍能发挥作用,在汛后利用垮塌石笼作为基脚在其上补做护岸工程效果更佳。     

黄河下游中牟九堡下延工程铅丝笼沉排坝应用效果分析

1九堡下延工程基本情况九堡下延工程为连续凹入型单一弯道河道整治工程，始建于1986年，现有丁坝23道，丁坝坝长、坝间距均为100m，工程的平面布置如图1。该工程在控导河势、护滩保堤方面起着重要作用。九堡下延工程的119～125号坝、135～141号坝为传统土石结构坝。126、127号坝的结构为散抛根坦、内衬有纺和无纺土工布各一层，在抢险中，土工布已断裂，作用不大。128～134号坝为铝丝笼沉排结构坝，其中的128～130、132～134号坝的沉排长11m．五月号坝的沉排长24m（沉排长垂直于坝轴线）。2铅丝宪沉排结构现的设计铅丝笼沉排结构坝的设计意…     

丁坝布置形式与河道整治目的的承辅关系

分析了不同整治目的的丁坝平面布置形式:①以稳定河势为目的的丁坝布置形式;②以保证航运为整治目的的丁坝布置形式;③以适应河口感潮河段的丁坝布置形式;④以护岸固滩和保护海塘工程安全为目的的丁坝布置形式。研究发现:根据河流整治目的不同,应采用不同的丁坝平面布置形式;除为适应河口感潮段双向水流动力作用采用正挑丁坝外,其余整治目的的丁坝布置形式以下挑丁坝为宜。     

黄河宁夏青石河段丁坝间距研究

通过对丁坝防护弯道的效果分析,认为丁坝间距不仅会影响坝头的局部冲刷深度,而且会影响丁坝防护弯道的效果。据此,借助模型试验及理论研究成果,分析不同工程边界条件下施工期流量、整治流量及20 a一遇设防流量下的水流流态、局部冲刷和河势演变,并从丁坝间距与丁坝所在河段的位置有关的角度出发,分析了凹岸丁坝群的丁坝间距与丁坝坝长的关系。研究表明:1.1倍坝长丁坝间距和1.5倍坝长丁坝间距对水流流态、局部冲刷和河势演变的影响差别均较小,结合理论研究认为来流方向与坝迎水面的夹角为60°～75°的坝段,丁坝间距应优先采用1.1倍坝长;来流方向与坝迎水面的夹角为20°～30°的坝段,丁坝间距宜采用2.0～2.6倍坝长。     

水力插板透水丁坝坝头冲刷坑深度模型试验

为探索水力插板透水丁坝减小坝头冲刷坑深度的最佳设计参数和布置方案,通过改变流量、丁坝挑角、丁坝透水率、丁坝长度进行单因素影响试验,得出坝头冲刷坑深度与各单因素的回归方程。从每组单因素试验结果中选择最佳试验水平,利用L9(34)正交试验设计表设计4因素3水平的正交试验。试验结果表明:4个单因素对水力插板透水丁坝坝头冲刷坑深度的影响从大到小依次为:丁坝透水率、流量、丁坝长度、丁坝挑角;在一定流量条件下,水力插板透水丁坝最佳布置方案的设计参数为丁坝透水率30%、丁坝长度30 cm、丁坝挑角60°。     

年楚河干流堤防整治工程设计方案优选

年楚河现状左岸堤防护坡多数为干砌石结构,岸坡稳定性较差,难以起到有效防护作用。文中通过护坡、护脚方案优选及弯道工程措施的选择,最终确定采用铅丝笼干砌石护坡、钢筋笼砌石护脚及丁坝弯道防护,作为年楚河干流左岸防洪堤整治工程的设计方案。     

黄河青石段河道整治工程典型坝垛模型试验

以实际地形、地貌及河道演变为基础,开展了黄河宁夏青石段河道整治工程典型坝垛模型试验,通过不同材料比例对根石备塌体、占体宽度等参数对比分析,结合以往设计成果进行分析,结果表明:青石段丁坝上跨角、坝前头、迎水面等部位,在考虑必要的安全冗余时,备塌体宽度宜取9 m,下跨角、背水面等部位备塌体宽度为5 m左右;在同一流量级下,铅丝笼与散石比例为7∶3时坝体抗冲稳定性更为理想;施工工艺中结合现场实际应采用"金包银"分区抛投与"汉堡包"层叠抛投相结合的根石抛投方式,施工时占体宽度宜为6 m。     

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。     

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.