滹沱河倒虹吸工程夯扩挤密碎石桩的施工

夯扩挤密碎石桩是以强力夯击碎石、矿渣、干硬性混凝土等材料，挤密周边土体与原地基形成复合地基，以提高地基承载力为加固原理的新型桩体，广泛应用于各种建筑工程地基处理。其具有工期短、造价低、技术可靠、施工简单、单桩承载力高等优点。     

复合载体夯扩桩在滹沱河倒虹吸基础处理中的应用

介绍了复合载体夯扩桩在滹沱河倒虹吸基础处理中的应用.复合载体挤密夯扩桩是用相同夯击能量和相同的贯入度控制桩体质量,可使处理深度范围内的地基土上下均匀,使松散砂土颗粒重新排列,可有效提高地基承载力和压缩模量,是一项值得大量推广的施工工艺.     

复合载体夯扩桩施工工艺

在地基工程中选用复合载体夯扩桩 (俗称垃圾桩 ) ,可使单桩竖向承载力提高 2倍以上 ,工程造价可降低 2 0 %～ 35 % ,可用建筑垃圾的红砖和碎石等做填充料夯入地基 ,减少环境的污染 ,是一种多方有益的桩型。     

端夯扩碎石桩复合地基现场试验研究

结合南水北调工程SG14标的端夯扩碎石桩施工,根据现场静载、静力触探和动力触探试验以及室内土工试验对端夯扩碎石桩复合地基的桩土应力比、承载力以及桩间土的挤密效果进行了分析。试验表明:带有桩端扩大头的夯扩碎石桩的桩土应力比一般碎石桩大,试验所得桩土应力比一般在[4.2,7.4]之间;桩土应力比值随荷载的增加呈现先增后减,并逐渐趋于稳定,桩土应力比值随桩长的增大而增大;夯扩碎石桩复合地基的沉降曲线(P-S曲线)呈渐变型,没有明显的拐点或变化点出现;单桩复合地基承载力随着桩长的增大,承载力也逐渐增大;夯扩碎石桩施工能有效提高桩间土的强度,同时,对改善地基的不均匀沉降也有很好的效果。     

载体桩在皖南某工程中的应用

载体桩,又称复合载体夯扩桩,指由干硬性混凝土及碎石填充料等经细长锤夯扩而形成的复合载体和钢筋混凝土桩身构成的桩,具有挤密地基、扩大桩端面积的双重作用。复合载体由干硬性混凝土、填充料和挤密土体组成。填充料是为了增强混凝土桩端下土体的挤密效果而填充的材料。碎砖、碎混凝土块、水泥拌和物、碎石、卵石及矿渣等都可以作为填充料。挤密土体是填充料周围被夯实挤密的土体。复合载体构造示意由于载体桩承载力主要来源于载体,且载体桩桩长较短,混凝土质量易保证。因而具有较高的性价比,在工业与民用建筑中得到了广泛应用。本文以载体桩在皖南某工程中的应用为实例,介绍了载体桩在该地区的应用。     

复合载体夯扩桩施工技术探讨

复合载体夯扩桩扩展基础是一种新型的工艺,重点研究复合载体夯扩桩特点、影响因素,通过桩承载力检验施工效果。     

复合载体夯扩桩在南水北调中线磁县段工程中的应用

南水北调中线磁县段输水渠道岩土地基,具轻微—中等震动液化或轻微—中等液化潜势,经过适宜的复合载体夯扩桩地基处理施工工艺有效地消除了地基液化；具体阐述了夯扩桩试桩目的、试桩过程、施工工艺、标准贯入度检测分析、桩间土液化判定,明确了夯扩桩布置形式、夯填材料每次填筑量、桩径、间距、桩长等技术参数.     

夯实水泥土挤密桩在湿陷吐生黄土地基中的应用

随着工程建设的飞速发展，地基处理手段也日趋多样化，复合地基由于其充分利用桩间土和桩共同作用的特有优势和相对低廉的工程造价得到了越来越广泛的应用。本工程应用的孔内深层强夯水泥土桩复合地基，是一种新型地基处理技术，由于施工速度快，无环境污染，造价低廉，施工质量易于控制，充分发挥了夯实水泥土桩的高承载力性能和水泥土桩的抗变形性能，并通过夯扩挤密桩间土消除地基土的湿陷性，取得了可观的社会和经济效益。     

夯扩碎石挤密桩在地基处理中的应用与分析

随着科技进步和工程建设事业的不断发展，夯扩碎石挤密桩得到了越来越广泛的推广和应用，它不仅能有效地消除液化，提高复合地基的承载力，而且造价低，施工简便。本文结合掌政变２２０ｋＶ变电所现场实践，从成桩原理、施工工艺及应用、质量控制及检测等方面对夯护碎石挤密桩进行了重点论述。     

夯扩桩扩大头效应和竖向承载力的研究

夯扩桩在成桩过程中会产生挤土效应。本文介绍了Vesic球形孔理论在夯扩桩扩大头方面的应用,推导出夯扩桩形成扩大头时引起的挤土影响半径,并结合工程实例分析提出夯扩桩单桩承载力的计算公式,经实践证明用该方法求得夯扩桩单桩承载力可满足工程应用。     

Call for Papers

正As the eldest and most distributed professional journal of water industry,Water Wastewater Engineering(W WE)gained very wide acceptance from the colleagues working in this field in this country since start publication in 1964.Now it is administrated by the Ministry of Construction of the People’s Republic of China and sponsored by the China Civil Engineering Society etc.     

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。     

SPATIAL AND TEMPORAL WATER QUALITY VARIABILITY IN AQUATIC HABITATS OF A CULTIVATED FLOODPLAIN

The floodplains of lowland rivers contain diverse aquatic habitats that provide valuable ecosystem services but are perturbed when intensively cultivated. Hydrologic, water chemistry and biological (fish) conditions in five aquatic habitats along the Coldwater River, Mississippi, were measured for more than 4 years: the river, two severed meanders that functioned as backwaters, a managed wetland and an ephemeral channel draining cultivated fields. Off‐channel habitats were connected to downstream regions 0.10% to 32% of the dry season and 24% to 67% of the wet season. The median temperatures for the five monitored sites ranged from 18°C to 23°C, the median total solids concentration for all sites was 135 mg L^?1, the median total phosphorus was 0.29 mg L^?1 and the median total nitrogen was 1.56 mg L^?1. Chemical and physical water quality displayed strong seasonal differences between the wet winter/spring and the dry summer/fall periods so that temporal variation consisted of gradual seasonal trends superimposed on strong diurnal variations. All off‐channel habitats exhibited periods of hypoxia and temperatures >30°C during the dry season. Between‐site gradients of water and habitat quality were strongly coupled to water depth and runoff loading. The rehabilitation of one backwater by increasing water depth and diverting agricultural runoff was associated with improved water quality and fish species richness relative to an adjacent untreated backwater. The diversion of polluted runoff and the use of water control structures to maintain greater water depth were observed to be effective management tools, but the former reduces the water supply to habitats that tend to dry up and the latter reduces connectivity. Published in 2011 by John Wiley & Sons, Ltd.     

Spatio‐temporal variation of gross CO2 and CH4 diffusive emissions from Australian reservoirs and natural aquatic ecosystems,and estimation of net reservoir emissions

Carbon dioxide (CO₂) and methane (CH₄) diffusive emissions were measured during two field surveys in Queensland and Tasmania, Australia, using the floating chamber method. Bubbling and degassing emissions in 2010 were estimated in Koombooloomba Dam reservoir using only inverted funnels and gas concentrations, respectively. A total of 14 reservoirs and 16 rivers and lakes were sampled from 2006 to 2010. Spatial variation was substantial within each water body, as well as between them. The main drivers of diffusive emission variation were physiographic region and climate, with a clear demarcation being observed between diffusive emissions from tropical Queensland and temperate Tasmania, and between the humid West Coast Range (Tasmania) and dry Central Plateau (Tasmania). Higher CO₂ and CH₄ diffusive emissions were observed during the dry season, when long water residence times would promote organic matter degradation. Estimated total gross emissions, including diffusive, bubbling and degassing emissions, for Koombooloomba Dam reservoir were about 1.5 × 10⁶ t CO₂eq km² per year, or 24 × 10⁶ t CO₂eq per year. This corresponds to a plant emission factor of 3.18 kg CO₂eq MWh^?1. Using an estimate of terrestrial emissions derived from literature data for the Tully River catchment area, rough estimated net emissions from the catchment area are about 44 kt CO₂eq per year, or 5.83 kg CO₂eq MWh^?1, which is in the lower range of the studied reservoirs.     

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.     

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.