旁多滑坡滑带土抗剪强度参数分析与确定

滑坡滑带土抗剪强度参数是滑坡稳定性分析和治理工程设计的最基本、最重要参数,它的大小及其变化直接影响到滑坡稳定性的计算,并由此得到不同的结果。通过室内试验、反算分析方法、类比法综合确定旁多滑坡滑带土的抗剪强度参数。指出该滑坡滑带土抗剪强度参数的确定和分析应采用多种方法,才可获得合理可行的结果。     

重庆羊角滑坡群滑带土抗剪强度研究

羊角滑坡群是乌江白马航电枢纽坝前的一个巨型滑坡群,该滑坡群的稳定与否,对白马航电枢纽的安全运行至关重要.为能给该滑坡群的治理工程设计和稳定分析提供准确的强度参数,对该滑坡群中各滑坡的滑带土抗剪强度进行研究.采用滑带土室内试验、现场大剪试验、反演分析等方法,确定了羊角滑坡群各滑带土的抗剪强度参数,为工程设计提供了可靠的数...     

基于环剪试验的滑带土抗剪强度特性研究

以某水电站下游一大型滑坡千枚碎屑岩滑带土为研究对象,在室内模拟滑带土所受的天然状态条件,利用环剪仪研究了滑带土重塑样在不同法向应力与剪切速率下的抗剪强度特性。试验结果表明:滑带土的峰值强度和残余强度均随法向压力的增大而增大且有较强的线性关系,同时法向压力越大,试样达到残余强度所需要的剪切位移也会越小;剪切速率越大,滑带土的峰值强度也会越大,同时达到残余强度所需要的位移也会越大,但剪切速率大小对残余强度几乎没有影响,峰值强度参数与剪切速率之间可用对数关系拟合;剪切速率对滑带土的剪切面形态也有重要影响。     

蠕滑滑坡滑带土强度及其参数特性试验研究

金坪子滑坡Ⅱ区为一巨型蠕滑滑坡,为了研究该滑坡在诱发因素影响下的强度变化规律,以滑坡Ⅱ区滑带土为研究对象,通过不同剪切速率、不同含水率和正应力下的环剪试验,研究了其强度特性,结果表明:滑带土应变软化现象明显,已达到稳定残余状态的滑带土随着剪切速率的改变其抗剪强度出现增大的现象,并且正应力越大,强度恢复的幅度越大,其原因可能是剪切速率的改变使其剪切模式发生了变化;峰值强度参数中黏聚力、内摩擦角均随含水率的增大而线性减小,但黏聚力的变化幅度比内摩擦角的大,残余黏聚力与含水率成负相关关系,残余内摩擦角变化很小。     

大型滑坡滑带土强度参数取值试验研究

结合强度再生理论和土的压缩定律,以白龙江沙圈坝大型滑坡为例,对滑坡泥质物滑带土强度参数取值进行了试验研究.通过室内仿真重力压密试验,获得滑带土不同压力作用下孔隙比的变化特征,并采用试验获得的饱和度,计算纵剖面上各个部位滑带土的基本物理指标.通过原状样与仿真样的物理指标及强度指标试验,建立相关关系式,计算了滑坡各地段滑带土的综合抗剪强度参数.     

反算法在某滑坡稳定性评价中的应用

目前,结合试验资料和工程经验并通过已知稳定状态的边坡及滑面等条件情况下反算滑带土的抗剪强度参数应用很广.介绍了对某航道一侧的滑坡进行滑带土抗剪强度参数的反算过程,研究结果表明：抗剪强度参数c、妒对边坡稳定性的影响均较显著,其中妒的显著性强于c,同时给出了滑带土的抗剪强度参数建议值.     

滑带土长距离剪切强度及对滑坡启动的影响

滑带土的长距离剪切强度及其变化规律是滑坡启动的主要控制性因素之一,但是目前的常规直剪和三轴剪切试验还无法实现长距离剪切。为了研究滑带土的长距离剪切强度变化规律及对滑坡启动的影响,以四川省达县青宁乡滑坡为例,取其滑带土进行环剪试验,获得滑带土的长距离剪切强度变化规律,并与滑坡过程和运动特征进行对比分析。结果表明,滑带土长距离剪切强度变化规律与滑坡的启动过程较为吻合,滑坡首先受到降雨等因素触发开始变形和缓慢滑动,此时滑带土受到滑体的剪切,由于剪缩效应孔隙水压力迅速增大,导致剪切强度迅速减小,当小于某一临界值时,滑体开始加速并快速滑动。研究结论对类似的研究有一定的参考价值,可以为滑坡的预测预报和防治提供理论依据。      

基于直剪试验的滑带土强度再生特征研究

边坡稳定性主要受控于滑动带或软弱面的强度,选择合适的滑带土强度参数对边坡稳定性分析及防护设计具有直接影响。以三峡库区巴东县某滑坡滑带土为研究对象,对其重塑土样进行了慢剪、渐进剪、反复剪以及固结反复剪等4种剪切试验,研究了在不同试验方案下试样的峰值强度、折减强度以及残余强度的变化。通过试验结果对比分析,发现渐进剪切试验中峰值强度略高于慢剪试验中的峰值强度,并且固结反复剪切试验中的折减强度和残余强度也均高于反复剪切试验中的相应的强度值,揭示了滑带土结构的强度再生现象。同时,基于试验结果的统计分析,探讨了轴向压应力对滑带土结构强度再生的影响,发现在轴向压应力为100k Pa时,滑带土试样强度再生现象最为明显。     

公路滑坡滑带土抗剪强度参数选取方法研究

以羊道沟滑坡为工程实例,研究滑带土抗剪强度参数选取方法。利用反演分析结合室内试验和经验系数,得出滑带土抗剪强度参数(c、φ)值。研究表明:反演分析与多种方法的综合确定的滑带土抗剪强度参数更为合理,能有效地满足工程要求。     

滑带土抗剪强度与其矿物成分典型相关性分析

滑带土抗剪强度特性是影响滑坡稳定性状态、控制滑坡变形演化过程的关键因素,而滑带土矿物成分又是决定其抗剪强度特性的重要内因之一。以三峡库区吊钟坝滑坡群Ⅰ-1号滑坡滑带土为研究对象,探讨了滑带土矿物成分在不同饱水时间下的变化规律。结合相应饱水条件下滑带土的抗剪强度数值,分析了滑带土抗剪强度与其矿物成分间的典型相关性,以期进一步解释不同矿物成分在滑带土抗剪强度特性中所起的作用。研究结果表明,随着饱水时间的延长,滑带土中黏土矿物的相对含量先降低后趋于稳定;滑带土抗剪强度与其矿物成分表现出明显的相关性,影响滑带土凝聚力和内摩擦角峰值的主要矿物为蒙脱石和石英,影响滑带土凝聚力残余值的主要矿物为绿泥石。     

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.