砂砾石土灌浆浆液扩散半径试验研究

砂砾石层灌浆施工中,水泥浆液的扩散半径决定着灌浆孔的布置和浆液消耗量,也是选择工艺参数、评价灌浆效果的重要依据,因此,水泥浆液的扩散半径是灌浆施工中非常重要的参数。通过设计正交试验,对影响水泥浆液扩散半径的几个因素(水灰比、孔隙比、灌浆压力)进行了试验研究。试验结果表明:水灰比是影响水泥浆液扩散半径最显著的因素,水泥浆液的水灰比越大,浆液中的多余水分越多,对水泥浆液流动性能的改善越显著。     

砂砾石土渗透注浆浆液扩散规律及扩散半径影响因素试验研究

注浆技术在砂砾石土等水利工程的建设中发挥着越来越重要的作用,但是注浆技术存在理论研究滞后于工程实践需要的现象,需要对浆液扩散规律及浆液扩散半径等进行研究。通过设计试验,将拌合水泥浆用的自来水加热并插入温度传感器的方法,来探测水泥浆液在砂砾石层中的扩散过程;并通过正交试验,分析孔隙比e、水灰比m、灌浆压力p等各因素对扩散半径的影响。试验结果表明,浆液扩散过程中其时间t与扩散半径R呈较好的三次函数关系,这与Magg公式基本一致;而在水泥浆液的扩散半径方面,相对于孔隙比和灌浆压力,水灰比起着更显著的影响。本试验工作为砂砾石土灌浆技术提供了有益探索。     

某级配砂砾石灌浆试验研究

在工程兴建中对砂砾石层进行灌浆加固处理具有非常重要的意义。灌浆工程是隐蔽工程,砂砾石地层形态又复杂多变,在砂砾石层灌浆浆液的扩散半径及结石体强度等灌浆效果方面存在较大的不可预测性。对我国西北、西南地区广泛分布的砂砾石层进行了颗粒试配,并在实验室内开展了不同配比、不同组分的水泥灌浆试验研究。试验结果表明:水泥浆液的扩散半径基本上随水灰比的增加而增大,与浆液自身的物理力学性质密切相关;砂料结石体的抗压强度随水灰比的增加而减小,但是由于砂石料的内部结构极其复杂,使得试样的抗压强度离散性极大。试验所得结果可初步指导现场灌浆施工。更多还原     

坝基灌浆若干问题刍议

对坝基灌浆中砂砾石层可灌性，灌浆材料，浆液扩散半径，充填式灌浆寿命，串浆孔，固结灌浆压力，固结灌浆压水试验标准，稀浆和浓浆闭浆问题等，提出粗浅分析，以供参考。     

坝下砂砾石层劈裂注浆浆液扩散半径试验研究

冲洪积砂砾石层是水利和桥梁工程建设中常见的地质问题.文章以辽宁省小望海水库大坝加高加固工程为例,利用室内试验的方法研究了水灰比、注浆压力以及砂砾石层的渗透系数对砂砾石层劈裂注浆的浆液扩散的影响,结论可以为注浆施工设计提供必要的借鉴和支持.     

坝基灌浆若干问题刍议

坝基灌浆中对砂砾石层可灌性、灌浆材料、浆液扩散半径、充填式灌浆寿命、串浆孔、固结灌浆压水试验标准、稀浆与浓浆闭浆问题等，提出粗浅意见。以供商榷。     

砂砾石层帷幕灌浆施工技术研究与应用

砂砾石层具有渗透孔隙分布不均匀、渗透系数分布不均匀、胶结性差的特点,砂砾石层灌浆具有成孔困难、钻进中塌孔、"吃水不吃浆"、扩散半径差异大等问题,对防渗成幕影响较大。由于里底电站左岸灌浆排水洞砂砾石层中小于0.5mm的砂含量约为51.43%,且小于0.075mm黏粒约20.59%,细砂以下含量较大,防渗难点突出。以砂含量高为例,通过砂砾石层帷幕灌浆生产试验,推荐有针对性的帷幕灌浆技术参数、施工方法、灌浆材料等,确保砂砾石层帷幕防渗满足设计要求,同时消除古河槽进口高程低于正常蓄水位的渗漏及渗漏引起渗透破坏的可能性。     

砂砾石层可灌性分析与探讨

本文在前人研究的基础上,综合考虑各影响因素,从实用性的角度给出了可灌性的定义,分析了砂砾石层地质特性、浆液性能、灌浆压力以及防渗标准对可灌性的影响,在此基础上,结合笔者关于可灌性的认识,建立了砂砾石层可灌性准则,为今后砂砾石层灌浆提供技术指导。     

水位降落条件下非稳定渗流试验研究

水位降落时产生的非稳定渗流场对坝坡的渗流和稳定影响较大。通过砂槽模型室内试验模拟了粉砂、细砂、黏土等多种材质的边坡在水位降落过程中的非稳定渗流物理过程,分析了水位降落过程中上游边坡的渗流场特点,比较了不同边坡材料、渗透特性、坡比和水位降落速度的泄水过程中边坡渗流场自由面形式和等势线变化特点,重点研究了给水度μ、渗透系数k、库水位降落的速度v对自由面最高点、上游边坡中的孔隙水压力、坡降的影响,定量分析了水位降落时k/μv判断骤降、缓降、快降的标准,探讨了非稳定渗流浸润线的计算公式。结果表明：渗透系数小、给水度大的土坡在水位降落过程中产生的上游边坡孔隙水压力值和渗透坡降较大,非稳定流场自由面最高点位置也更高;水位降落时的上游边坡渗流方向指向坡面;浸润线最高点高度与坡前水深的比值h0/H与降落时间t/T间存在线性关系,k/μv作为判断骤缓降的指标与其线性系数呈指数关系。     

复合膏浆渗透扩散的二维离散元模拟分析

针对现有注浆理论难以对岩土体中的浆液在空隙及裂隙通道网络中的真实扩散规律进行准确描述的问题,本文从连续性方程的角度出发,运用二维颗粒流程序(PFC2D)建立数值模型,模拟研究注浆压力、注浆时间及砂卵石层渗透系数对复合膏浆在砂卵石层渗透扩散过程中的扩散半径的影响,总结规律并利用非线性拟合得出各因素与复合膏浆渗透扩散半径间的关系式。结合现场注水试验及开挖结果,得到与模拟基本一致的结果,所得成果可为工程施工提供一定的理论支撑和指导。     

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.