川藏铁路工程破碎岩体力学参数取值研究

为研究破碎岩体的力学特性,获取准确的工程力学参数,利用川藏铁路某场址区的勘探平硐,基于工程岩体质量分级、现场岩体力学试验和现场模型试验反演分析等方法,对破碎岩体的力学特性及参数取值进行研究。结果表明：对于破碎岩体,基于工程岩体质量级别确定的岩体参数值可能存在一定偏差,在无现场试验数据时,应进行充分论证参考使用;现场岩体力学试验是获取岩体力学参数的主要手段,其参数成果更为准确、更具代表性;基于现场模型试验反演分析获取的岩体力学参数可反映岩体在工程环境下的综合性状特征,可作为现场岩体力学试验参数取值的补充和校验。在川藏铁路工程建设过程中,破碎岩体的力学参数应主要基于现场岩体力学试验,并结合工程地质条件和工程应用环境综合分析确定。     

怒江松塔水电站坝址区岩体力学性质试验研究

对怒江松塔水电站坝址区主要岩层进行了较系统的试验研究,包括岩体结构的野外调查、岩块室内试验及岩体力学参数经验估算等.对各种试验数据进行了分析整理,得到了岩块的物理力学性质参数.然后用岩体工程分类及Hock-Brown经验方法对各类岩体的力学参数进行了估算.在分析对比基础上,并考虑岩体所处地质条件,给出了各种岩体的计算参数建议值,为水电站大坝设计提供计算参数.     

基于随机-关联空间插值法的工程岩体力学参数确定

岩体力学参数在空间上存在的结构关联性和随机不确定性是影响工程岩体力学参数设计取值的客观因素之一。基于地质统计学理论,提出随机-关联空间插值法,在工程岩体力学参数概率分布未知的情况下,利用样本矩替换母体矩,描述工程岩体力学参数的随机性,利用变差函数描述样本点之间、样本点和插值点之间的工程岩体力学参数关联性,建立岩体力学参数的空间分布模型,并通过克里格法对场地中的工程岩体力学参数进行空间插值。结合工程实例,在力学参数概率分布未知的情况下建立其概率分布模型;选择不同数量的有效样本对比分析该方法本身对样本数量的依赖性问题;探讨该方法的应用范围以及针对其他情况提出的相应措施,为后续研究打下基础。与试验结果对比,工程实际中3种不同样本的岩体力学参数指标相对误差分别为4.2,4.4,5.3,估值结果可作为工程设计取值的参考依据。     

黄石板岩山危岩岩体力学性质试验研究

 对区内主要岩层进行了较系统的试验研究，包括岩体结构的野外调查、岩块与结构面室内试验、岩体力学原位试验及岩体力学参数经验估算等。对各种试验数据进行了分析整理，得到了岩块、结构面及岩体的物理力学性质参数。然后用岩体分类及Hoek Brown经验方法对各类岩体的力学参数进行了估算。在分析对比基础上，并考虑岩体所处地质条件，给出了各种岩体的计算参数建议值。有限元计算结果表明，参数建议值能较好地反映危岩区岩体的力学性质。     

基于非线性方法的碎裂结构岩体力学参数分析

采用常规的试验方法对碎裂结构岩体的力学参数进行研究存在一定的局限性,容易受现场条件和尺寸效应的影响,而基于非线性方法的参数分析在一定程度上能够很好地对碎裂岩体的力学参数进行预测。以前坪水库溢洪道碎裂结构岩体为例,在资料收集的基础上建立了岩体力学参数数据库,通过因子分析法将数据库中影响岩体力学参数确定的多个指标进行简化降维后,再结合非线性BP神经网络分析法对工程区岩体的部分力学参数进行预测;在室内外试验数据和现场工程地质条件分析的基础上,运用H-B强度准则对工程区域内不同岩层的岩体力学参数值进行了计算;将预测结果和计算结果进行对比分析后,对工程区的岩体力学参数取值提出了建议。     

水利水电工程岩体力学参数数据库的开发和应用实例

以湖北省水利水电工程岩体力学参数经验取值研究成果数据为基础,介绍水利水电工程岩体力学参数数据库建立的基本方法及关键代码。采用湖北省地区通用的地基承载力、压缩模量数据及水利工程设计常用地质参数等大量岩土参数数据,开发了"岩土参数经验取值系统"。该软件具有界面友好、操作性简单的优点,适合推广。     

丹江口水利枢纽岩石力学试验研究

丹江口水利枢纽坝基岩石力学试验研究历时18 a,先后开展了岩块物理力学性质、岩体抗剪强度、岩体变形特性及现场岩体动力弹性参数试验研究.对历年岩石力学试验成果进行了汇总,并根据试验和地质条件进行了分析整理.根据岩体的强度和完整性将坝基岩体分为3类,分别提出了岩石力学试验参数建议值.     

中美水电标准岩体及结构面力学参数取值方法对比研究

从试验方法、试验数据整理及参数取值方法等几个方面,对比研究中美水电标准在岩体及结构面力学参数取值方面存在的差异。在国外工程抗滑稳定性分析计算过程中,应充分了解岩体及结构面力学参数的使用条件,避免随意混用、套用中美标准。在国外工程实践过程中,应积极主动地学习国际通用的一些参数取值分析方法,并针对具体工程特点开展中美标准力学参数取值方法的对比分析,让业主咨询工程师理解并接受我国标准的参数取值方法,为我国水电标准全面走出国门打下基础。     

海甸峡水电站软岩坝基物理力学参数建议值的选取

针对海甸峡水电站软岩坝基进行了大量取样岩石室内试验和现场岩体原位测试,笔者对试验成果进行分类统计分析汇总,舍去不合理的离散值,以整理后的试验值作为标准值,再结合水电站工程具体水工建筑物地基的工程地质条件进行调整。依据并遵循相关规程规范中岩土物理力学参数取值原则,合理选取了海甸峡水电站软岩坝基物理力学参数建议值,供水工设计人员使用。     

国际水电工程岩体抗剪强度参数估算方法

结合国外某水电工程实例,介绍了国外岩体工程中广泛应用的Hoek-Brown经验强度准则。摘录国外某水电工程地质勘察报告中岩体抗剪强度参数估算成果,与我国规范地质建议值比较,得出结论:运用Hoek-Brown准则估算的岩体抗剪强度参数与我国规范地质建议值相比值略小、值偏大。最后提出,运用Hoek-Brown准则估算岩体抗剪强度参数,核心参数地质强度指标GSI主要依赖地质师的经验判断取值,所以,地质师的工程经验判断是关键,这一点与国内水电工程地质工作是一致的。     

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。     

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.     

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.     

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。     

Desiccation and recolonization of phytobenthos in a regulated desert river: Colorado River at Lees Ferry,Arizona, USA

We tested the recolonization of the phytobenthic community in the tailwaters of Glen Canyon Dam following long- and short-term experimentally induced desiccation. The response of Cladophora glomerata, Oscillatoria spp., miscellaneous phytobenthos species and periphyton was studied over 18 weeks using three treatments: (1) undisturbed control cobbles from the submerged zone; (2) cobbles desiccated and replaced into the submerged zone; and (3) cobbles desiccated and replaced into the varial zone. Periphyton density and compositional response resulting from these treatments were also examined. Desiccation treatments were significantly different in biomass from controls throughout the study. The biomass of desiccated and replaced river cobbles averaged <30% of the controls for C. glomerata and periphyton during the 18-week recolonization period. In contrast, the biomass of the control Oscillatoria and miscellaneous phytobenthos species averaged only 3 and 50% of that in the desiccation treatments, respectively. Cladophora, the dominant alga, comprised 77% of the phytobenthic biomass. A significant positive relationship between discharge, Cladophora and periphyton biomass was present in all treatments, while there was a negative relationship with discharge for Oscillatoria and miscellaneous phytobenthos species. There was a significant inverse correlation, as well as a pattern of separate biomass dominance, between C. glomerata and Oscillatoria. Cladophora was the dominant phytobenthos species on cobbles below the baseflow and Oscillatoria was dominant on cobbles in the varial zone. In general, the Cladophora biomass decreased under intermittent drying conditions, while Oscillatoria declined under permanently wet conditions. Diatom composition was not significantly different between treatments; however, their density was lower on desiccated cobbles. Diatom density on desiccated cobbles in the submerged and varial zones averaged 69 and 42% of that of the controls, respectively. Recovery and maintenance of benthic resources are hindered by fluctuating flow regimes driven by electricity and irrigation requirements. Repeated desiccation of the phytobenthos has major effects on the bottom-up interactions in the Colorado River ecosystem. © 1998 John Wiley & Sons, Ltd.