轴对称条件下水泥土强度特性试验研究

通过水泥土等p三轴剪切试验、常规三轴固结排水剪切试验(CD)与三轴固结不排水剪切试验(CU),对水泥土力学特性进行研究,讨论水泥土的应力～应变曲线变化特点和强度特性。试验结果表明:水泥土的应力～应变曲线为软化型,软化程度与围压有关;不同应力路径对水泥土强度有一定的影响,但影响程度较弱;小围压作用下水泥土具有剪胀性,类似强超固结土;高围压下,水泥土类似弱超固结土;残余强度均随围压的增加呈线性增大,CD试验残余强度高于CU试验,残余强度与峰值强度的比值随围压的增大而增大,增大速率逐渐减小;水泥土CU试验的有效强度包线与CD试样强度包线基本一致。     

轴对称条件下水泥土强度特性试验研究

通过水泥土等P三轴剪切试验、常规三轴固结排水剪切试验(CD)与三轴固结不排水剪切试 验(CU),对水泥土力学特性进行研究,讨论水泥土的应力一应变曲线变化特点和强度特性。试验结 果表明:水泥土的应力一应变曲线为软化型,软化程度与围压有关;不同应力路径对水泥土强度有一 定的影响,但影响程度较弱;小围压作用下水泥土具有剪胀性,类似强超固结土;高围压下,水泥土 类似弱超固结土;残余强度均随围压的增加呈线性增大,CD试验残余强度高于CU试验,残余强度 与峰值强度的比值随围压的增大而增大,增大速率逐渐减小;水泥土CU试验的有效强度包线与CD 试样强度包线基本一致。     

掺砂水泥复合土力学性能研究

水泥复合土不同围压下的常规三轴试验和无侧限抗压强度试验结果表明:在水泥土中掺入一定量的砂,可以提高水泥土的无侧限抗压强度;在有围压作用的情况下,掺砂水泥复合土的偏应力—应变关系曲线有明显的峰值,偏应力—应变关系曲线属加工软化型,其残余强度和破坏应变随着围压的增大而增大。通过SEM电镜扫描照片,进一步从微观角度分析了水泥复合土的固化机理。     

不同含水比贵阳原状红黏土CU三轴试验研究

为研究贵阳地区原状红黏土在CU三轴试验下的力学性质,采取原状土试样制备的方法,得到三种不同含水比的原状红黏土试样,进行CU三轴试验。试验得到了贵阳原状红黏土在不同围压、不同含水比下的应力-应变关系、破坏形式以及孔隙压力变化规律,采用Mohr-Coulomb准则和规范法得到抗剪强度指标且分析了含水比对抗剪强度指标的影响。研究结果表明:(1)贵阳原状红黏土的应力-应变关系、孔隙压力均出现"驼峰型"软化特性,且围压越低、含水比越低,软化现象越明显,但也有少部分试样表现出微弱的硬化特征;(2)CU三轴试验中,随含水比的减小、围压的增大,贵阳原状红黏土试样的破坏形态由剪切破坏转变为鼓状破坏;(3)抗剪强度指标与含水比呈线性趋势变化,其中内摩擦角与含水比呈正相关,黏聚力与含水比呈负相关。     

滑带土含水率与力学参数关系试验研究

为研究降雨型滑坡滑带土力学性质的变化规律,通过三轴剪切试验,在不同含水率下对某滑坡滑带土的应力-应变关系、抗剪强度与变形模量以及强度指标进行了初步研究。研究表明,含水率对滑带应力-应变关系发展模式影响显著。当含水率小于塑限时,应力-应变关系的发展模式为弹性变形→应变硬化→出现峰值→应变软化,出现剪切破坏面;而当含水率大于塑限时,应力-应变关系发展模式基本上是应变硬化,出现鼓胀破坏。随含水率增大,滑带土抗剪强度降低,可分为3个阶段:塑限含水率以前,抗剪强度变化不明显;塑限含水率至17%(液限与塑限含水率的平均值附近)时,抗剪强度下降速率最大;随后变缓。随含水率增大,滑带土黏聚力降低,近似符合双线性关系。     

围压和密度对粗粒料临界状态力学特性的影响

粗粒料的力学特性不仅取决于有效围压,还与密实程度密切相关。通过4组不同初始干密度粗粒料的大型三轴固结排水剪切试验,研究了围压和密度对粗粒料临界状态力学特性的影响。试验结果表明:软化型应力应变曲线破坏状态偏应力大于相变状态偏应力,而相变状态偏应力与临界状态偏应力较为接近;不同围压、不同密度的试验,随着剪切的进行,偏应力与平均正应力的应力比逐渐趋向于临界应力比,软化型试验应力比曲线呈单驼峰型形态,硬化型试验应力比曲线呈爬升型形态;临界孔隙比随临界平均正应力的增大而减小,随初始孔隙比的增大基本呈线性增大。研究成果可为特征状态参数研究和临界状态本构模型的建立提供依据。     

不同期龄塑性混凝土力学性能试验研究

对养护期龄为7,14,28,90 d的塑性混凝土进行三轴压缩试验,实测不同围压状态下试件的应力-应变曲线及强度参数,分析不同养护期龄及试验围压对强度、应力-应变关系的影响。试验结果表明:塑性混凝土在低围压时表现出软化性,破坏偏应力与破坏应变较小,随着围压提高塑性混凝土应力应变曲线软化趋势减弱,并且随着围压的提高其破坏偏应力显著提高。塑性混凝土在不同围压下均表现出先剪缩后剪涨的特点,且随着围压升高其剪缩的趋势增大剪涨的趋势减小。双曲线模型参数K值随养护期龄的发展而增大,双曲线模型参数n、F、破坏比Rf值随养护期龄的发展而减小。相同养护期龄内塑性混凝土破坏偏应力随围压的增大而增大,相同围压下其破坏偏应力随养护期龄的发展而增大。凝聚力随期龄发展而增大,内摩擦角受养护期龄变化影响较小。     

密实度对砂卵砾石料强度及变形特性的影响

为研究试样相对密度对砂卵砾石料强度及变形特性的影响,对4组不同相对密度的砂卵砾石料进行不同围压下的中型三轴固结排水剪切试验。试验结果表明:在试验的相对密度范围内,随着围压增大,相对密度小的试样应力应变曲线硬化特征逐渐明显,而相对密度大的试样无论围压大小,应力应变曲线都呈应变软化型;试样在剪切过程中均表现出不同程度的剪胀性;试样抗剪强度指标φ和φ0随着试样相对密度Dr增大而增大,c和Δφ随Dr增大而减小,并建立了试样抗剪强度与相对密度的函数关系式;割线模量、切线体积模量都随Dr增大而增大,可近似用线性关系表示。     

水泥改性膨胀土的非饱和强度试验研究

改性膨胀土的主要目的是减小膨胀土的膨胀潜势和提高膨胀土的强度。选取南水北调中线工程河南南阳段膨胀土,采用非饱和直剪仪进行素土与水泥改性土控制吸力条件下的直剪试验。试验表明,3%的水泥掺量使得膨胀土的自由膨胀率由51%下降到30%。在不同的基质吸力和竖向压力下素土试样由于结构性遭到彻底的破坏应力应变关系表现为应变硬化特性,而水泥改性膨胀土的应力应变关系表现为应变软化特性。水泥改性在提高膨胀土饱和抗剪强度参数c′、φ′的同时,也使得非饱和抗剪强度参数φb有所增大。试验成果为膨胀土现场水泥改性的设计施工提供了科学的、有价值的依据。     

聚丙烯纤维硅粉水泥土力学性质试验研究

在硅粉水泥土中掺加聚丙烯纤维配制试样,进行无侧限抗压强度试验和不同围压下的三轴试验,结果表明:聚丙烯纤维的掺加可以有效提高水泥土体的强度,且土体强度随纤维掺加量的增加而增强;随着围压的提高,水泥土试件的破坏应力和破坏应变均逐渐增大,掺入聚丙烯纤维的水泥土试件在不同围压下的破坏应力均高于同条件下未掺加纤维的试件。     

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.     

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.     

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。     

Impacts of Microcystis on algal biodiversity and use of new technology to remove Microcystis and dissolved nutrients

Cyanobacteria often dominate eutrophic lakes, outcompeting green algae that are required by fish and zooplankton. This study was undertaken to ascertain the impact of the cyanobacterium, Microcystis, on algal biodiversity. Under laboratory conditions, we found that the presence of Microcystis decreased phyla richness by 58%, phyla evenness by 47%, genera richness by 66% and genera evenness by 51%. Analysis by mixed anova s demonstrated a significant interaction between treatment and time and confirmed a significant reduction in richness and evenness of phyla and genera. We also conducted a phosphate restriction assay on the algae in Mason Lake (Irvine, CA, USA) and found that the threshold needed for algal growth there was 0.02 mg L^?1 PO₄. A pilot study was then conducted to test the effectiveness of the Blue Pro? water treatment facility in removal of this colonial organism from Mason Lake, in addition to removal of dissolved nutrients required for its growth. We measured a 97% reduction in Microcystis cells, a 72% reduction in chlorophyll‐a, and a 96% reduction in phosphate after just one 10 min cycle through the unit. Our study demonstrated that removal of Microcystis colonies may allow green algae to increase in numbers. This may improve algal biodiversity, which will benefit zooplankton and fishes.     

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.     

库水波动下库岸边坡地下水浸润线解析解及误差分析

解析法是库岸边坡地下水浸润线计算中便于实际应用的方法,但该方法须基于若干假定并对潜水运动基本方程线性化后才能求解。针对各假定和线性化过程建立不同的地下水渗流数学模型,用解析法和有限元法解答上述数学模型,分析各误差大小及其规律。结果表明：库岸垂直处理带来的误差要小于方程线性化处理和不考虑非饱和渗流带来的误差,而且它们都随渗透系数变大而减小;在三峡库区库水调度情况下,假定库水位等速变化带来的误差对大多岸坡而言可以忽略;计算库岸边坡地下水浸润线时,解析法只适用于水位变化幅度相比含水层厚度较小,且几何边界规则、岩土结构简单、岩土体渗透性较好时的情况。     

簸箕李引黄灌区水沙分布及优化调度的经验

灌区利用水沙观测所取得的资料和试验数据，运用水沙运动力学理论，总结分析和揭示了灌区水沙分布的规律和特点。在此基础上，结合灌区的实际运行情况，围绕减少骨干渠道的淤积进行探讨、研究，进而，优化水沙调度方案。该方案实施后，骨干渠道减旅伴效果明显，取得了成功的经验。     

小湾水库大坝防渗面板及其裂缝的加固处理

小湾水库大坝防渗面板整体抗渗性能差,且存在多条裂缝,通过对面板钢丝网喷涂丙乳砂浆加固处理及其裂缝修补,大坝渗漏量明显减少,且左岸上灌浆廊道内及大坝下游坝面92～93 m高程下廊道入口处原有小股射流全部消失.