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1.
邓刚  沈珠江 《水利学报》2005,36(12):1414-1419
在岩土破损力学理论的框架内,将结构性黏土看作由不同渗透性能的结构块和结构带组成的二元介质材料,建立了结构性黏土的二元介质渗流模型。进行了一维固结计算,结果说明该模型能与现有二元介质应力应变关系配套进行变形和渗流耦合分析,并能较好地描述结构性黏土的固结过程。  相似文献   

2.
黄土的二元介质模型   总被引:24,自引:3,他引:21  
把天然黄土看作由胶结块和软弱带组成的非均质材料,建议了一个黄土二元介质模型。文中首先分析了胶结块的浸水软化和应变软化机理,在此基础上建立了胶结块和软弱带的应力-应变关系和相应的破损演化规律。模型参数可以通过原状试样和重塑试样的常规试验测定。  相似文献   

3.
基于多重介质理论,建立了填料床二元渗流计算模型,认为填料床的渗流具有二元性质:其一,水通过多孔材料颗粒之间的分析流动,渗流通畅,流速较大;其二,水通过多孔材料颗粒内的孔隙渗流,渗流不甚通畅,流速较慢。二元模型描述了这种差别,并得出了通过二者渗流流量的比值。认为多孔材料的孔隙率大于0.6时,通过多孔材料的流量占总流量的比例接近30%。  相似文献   

4.
结构性土的二元介质模型   总被引:12,自引:1,他引:11  
刘恩龙  沈珠江 《水利学报》2005,36(4):0391-0395
本文在岩土破损力学的理论框架内,认为弹脆性元在破损以前的变形特性可以用理想的弹性材料描述,弹脆性元破损后转化成的弹塑性元的变形和破坏特性可以用修正的剑桥模型来描述,通过引入反映破损过程的结构参数(破损参数和应力比),建立了结构性土的二元介质模型。最后与人工制备结构性黏土的等向压缩试验和原状海积软土的三轴排水剪切试验进行对比,表明所建立的模型可以较好的描述结构性土的变形特性。  相似文献   

5.
杜小凯  任青文  杨曼 《水力发电》2007,33(12):25-28
研究裂隙岩体渗流的模型有等效连续介质模型、裂隙网络模型和双重介质模型等。等效连续介质模型受到样本单元体REV的限制,裂隙网络模型和双重介质模型复杂,处理难度较大。为此,在分区的同时考虑结构面和岩块的渗透特性,并考虑结构面法向与岩块之间的水力交换,利用两类介质接触处水头相等及节点流量平衡建立新的模型。对所建立模型的渗流场有限元公式进行推导,并通过与试验结果对比验证了该模型的正确性及实用性。  相似文献   

6.
复杂裂隙岩体水力学模型的研究   总被引:7,自引:0,他引:7  
目前裂隙岩体水力学模型研究主要沿3个方向发展;即扩连续介质模型、离散介质模型和双重介质模型。3种模型各有其特点,但均存在计算工作量巨大和难以满足实际工程精度要求等缺陷,为避免这类缺陷,采用分形理论,并根据裂隙发育规模与工程尺度的关系,提出了基于岩体与流体相互作用的上述两种模型的耦合模型。对数目不多的高序次的起主要导水作用的大中型裂隙、断层、认为是具体的,采用离散介质模型;对由这些大中型裂隙、然后根  相似文献   

7.
在现有预测模型的基础上,结合南方红壤坡地养分流失特征,基于成因型和统计型规律分别提出了物理成因型养分流失预测模型、二元线性统计模型和二元非线性统计模型共三个养分流失预测模型,并通过小区试验获得的数据对模型进行检验,结果表明三个模型均可较准确地对养分流失量进行预测,其中二元线性回归模型对我国南方红壤坡地的养分流失量的预测精度较其它两个模型高。  相似文献   

8.
岩样变形特性的二元介质模拟   总被引:1,自引:0,他引:1  
围压低时岩石材料表现为应变软化。应变软化的合理描述对岩石工程非常重要。在岩土破损力学的理论框架内,认为加载过程中胶结元逐渐破损转化为摩擦元,二者共同抵抗外部荷载作用,胶结元(胶结块)在破损以前的应力应变特性可以用理想的弹脆性材料描述,胶结元破损后转化成的摩擦元(软弱带)的应力应变特性可以用硬化型弹塑性模型来描述。通过引入反映破损过程的破损参数(破损率和应变集中系数),建议了一个岩石材料的二元介质模型。最后与砂岩岩样的三轴试验结果进行了对比,表明所建议的模型具有较好的适用性。  相似文献   

9.
摘要:SWAT模型是一个具有较强物理机制的、长时段的流域水文模型。针对中国人类活动强烈的流域水循环特点,在二元水循环理论的指导下,以SWAT模型为基础,进行了灌溉和人工耗用水模块的开发和改进,构建了适用于此类区域的二元水循环模型。利用改进后的模型对全世界用水最为强烈的区域之一——天津市的水循环过程进行了模拟,结果表明,改进后的模型模拟的NASH效率系数从0.62提高到0.89,相关系数从0.79提高到0.91,比改进前有明显的提高。模型构建和改进的成功,对分布式水文模型在高强度人类活动影响流域的水资源水环境研究和管理将起到积极的作用。  相似文献   

10.
针对裂隙地下水渗流及溶质迁移多场耦合数学模型,综述模型研究的发展历程与阶段性成果,将现有模型 划分为基于不同介质概化的等效孔隙介质模型、多重介质模型、离散裂隙模型,基于不同耦合方法的非全耦合模 型与全耦合模型,以及基于不同模型推导途径的力学途径模型与混合耦合理论模型。针对该领域研究的关键科 学问题总结其发展趋势,探讨裂隙地下水渗流及溶质迁移多场耦合数学模型研究的难点及潜在发展方向,为裂隙 地下水流及溶质迁移研究提供理论参考。  相似文献   

11.
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。  相似文献   

12.
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.  相似文献   

13.
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.  相似文献   

14.
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.  相似文献   

15.
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.  相似文献   

16.
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。  相似文献   

17.
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).  相似文献   

18.
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.  相似文献   

19.
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。  相似文献   

20.
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.  相似文献   

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