不同倾角层状砂岩单轴压缩及数值模拟试验研究

地下层状岩体存在节理、断层等结构面,层状岩体是许多基础设施和地下工程的载体,层状岩体具有明显的各向异性。为探明具有不同结构面倾角岩石的力学性质和破裂模式对水利裂缝扩展的影响,人工制作不同角度结构面的岩石模型,并开展单轴压缩试验和ＦＬＡＣ3Ｄ数值模拟对岩样进行破裂模式和力学参数各向异性分析。结果表明当结构面倾角为0°时,试样发生劈裂破坏,宏观破裂面沿着结构面,结构面主导岩石的破坏模式;倾角为15°、30°和45°时,试样由劈裂张拉破坏逐渐转换为剪切破坏,宏观破坏面主要沿节理面发生,节理主导岩石破坏的作用开始逐渐削弱。倾角60°、75°和90°时,裂缝会穿过结构面,宏观破裂面不沿着节理层面。相同角度的饱水模型的单轴抗压强度明显降低,随着节理面倾角的减小,岩石单轴抗压强度出现先减小再增大的现象,图像趋势为“勺”形。研究结果可为矿区水力裂缝扩展趋势、岩层失稳破坏风险评估提供参考。     

单轴压缩下层状岩体的各项异性研究

层理对岩体强度和各向异性特征都有重要影响,为了详细的研究层理间距和倾角对岩体强度 各向异性特征的影响,通过对类层状岩体标准试样的单轴压缩试验,得出了试样的强度和弹性模量随层 理间距、倾角的变化规律,并深入分析了试样的破坏形态,最后通过理论计算对试验结果进行了验证。 研究结果表明:岩体强度随层理面倾角的增加近似呈“Ｕ”型变化的规律,并在60°左右达到最小值;岩体 的弹性模量随层理面倾角的变化规律总体上是以45°为分界点,近似呈“Ｖ”型变化;岩体的强度、弹性模 量、破坏机制和各向异性比受层理面间距的影响均较小,层理间距为10ｍｍ的试样各向异性比为4．72, 层理间距为20ｍｍ的试样各向异性比为4．46,均属于高各项异性水平;试样破坏机理主要是剪切滑移和 张拉破坏,以及两者的组合。     

内置单裂隙相似材料岩样破坏特性及电阻率变化特性试验研究

文章利用四极法进行了含不同倾角内置三维裂隙岩样单轴加载破坏过程中的电阻率变化测试,试验表明:预制内部三维裂隙对峰值强度和弹性模量均有劣化作用,α=0°和90°试件表现为拉伸破坏,0°α90°时,试件整体上属于拉剪破坏;此外,内置裂隙岩样的单轴峰值强度和弹性模量对裂隙倾角非常敏感,0°倾角岩样峰值强度最低,90°倾角岩样峰值强度仅次于完整试件峰值强度。轴向峰值应变受裂隙倾角的影响较大,完整岩样峰值应变较小,α=45°时轴向峰值应变最大。结合电阻率-应力-应变关系,可以看出电阻率变化与裂隙岩石破坏过程密切相关,由此对单轴压缩下裂隙岩石破坏的基本特征有了新的认识,为今后的研究提供了新的思路。     

层状岩体损伤破坏特征数值模拟

为更深入了解层状岩体的力学特性,首先基于细观损伤力学理论,运用体积平均化的方法,推导了微裂纹对岩体弹性柔度矩阵的贡献;然后基于不可逆热力学框架,导出了损伤矢量的损伤破坏方程;最后建立了层状岩体的损伤破坏本构模型,并通过数值计算模拟了层状岩体的损伤破坏特征,与室内试验结果吻合较好。巴西圆盘劈裂数值试验研究表明:岩体试样的破裂面均从加载点起裂;层理倾角0°、90°时,破裂面为通过加载中心和试样中心的近似平面,层理倾角为其他角度时,破裂面为偏离了加载中心的曲面。与室内试验结果对比可知,本文二次开发的本构模型能够较好地预测层状岩体渐进破坏的各向异性。     

层理特性对层状岩体剪切力学特性的影响研究

当前对层状岩体力学特性的研究多涉及抗压及抗拉特性,为研究层状岩体剪切破坏过程中的强度和弹性变形参数及破坏特征,通过基于人工制样方法,开展不同层理倾角、层理间距及层理粘结强度下层状岩体直剪试验,结果表明:随着层理倾角的增大,层状类岩体的抗剪强度指标呈现先增大、后减小、再增大的变化趋势,在３０°左右量值最大,在６０°左右量值最小;当层间粘结强度与岩层强度接近时,层理间距对其剪切特性的影响较小;层理粘结强度的提高会增强试样的抗剪强度。     

滑雪赛道结构面倾角对基岩破坏模式影响研究

岩体中结构面的空间产状分布是影响岩体变形及破坏模式的关键因素之一,节理岩体的破坏有不连续性,离散单元法成为研究节理岩体破坏模式的有效方法之一。以高山滑雪中心赛道基岩为对象,采用颗粒流离散单元方法对含有不同倾角节理的岩石试件进行数值试验,研究了不同倾角节理对岩石强度的影响以及岩石试件的破坏模式。结果表明:含节理面岩石试件的抗压强度显著低于基岩,节理面倾角对其抗压强度的影响随着角度的增大会出现一定程度的降低,当其数值不大于45°时,其影响并不明显;但当节理倾角大于45°时,抗压强度会开始发生显著的降低,达到75°时其强度值最低。     

动力荷载下软硬互层岩体力学特征

针对动力荷载下软硬互层岩体破坏问题,以汶川水磨沟滑坡层状岩体为研究对象,依据相似理论,制作软硬互层岩质试块,开展单轴压缩及变上下限等幅值循环荷载试验,研究其动力特性及破坏过程。结果表明：随岩层倾角的增大,其破坏模式为贯通层面的张拉破坏(0°～30°)、沿层面的剪切破坏(45°～75°)及沿层面的劈裂破坏(90°),而试样的强度及应变先增后减。对于相同倾角的试样,强度随加载频率及围压增大而增大。应变随加载频率增大而减小,随围压增大而增大。加载频率的增大会导致竖向拉张裂缝贯通、破裂程度降低。     

关于层状岩体抗拉强度测定方法的讨论

为了探究层状岩体抗拉强度合适的测定方法,将前人对巴西圆盘劈裂的理论和试验成果进行 了归纳总结;并在此基础上,对直接拉伸法进行理论分析,提出了合理的建议。研究表明:巴西圆盘劈裂 试验对试样的要求是在加载直径线两侧的层理构造和岩石材料均对称分布,只有这样,圆盘试样在线性 荷载作用下,内部应力才能对称分布,劈裂破坏面才会沿着加载直径方向穿过圆盘中心点,从而巴西劈 裂的理论计算公式才能得到满足;在直接拉伸试验中,试样的破坏形态和机理有三种沿层理面的张拉 破坏、沿层理面的剪切破坏、基质的张拉破坏,且抗拉强度均为σｔ＝Ｆ／Ａ;巴西圆盘劈裂试验的适用范 围不能盲目地扩大,对于层状岩体的抗拉强度测定方法,建议选用直接拉伸法。     

层理灰岩抗拉力学参数各向异性及破裂特征分析

山体斜坡在自重荷载或卸荷作用下常表现为侧向受拉,拉裂缝的形成及展布方向与层面产出状态密切相关。为探讨层理倾角对岩体抗拉力学特性与宏-细观破裂特征的影响,以三叠系大冶组中厚层状灰岩为研究对象,对0,15°,30°,45°,60°,75°,90°共7种倾角层理灰岩岩样进行巴西劈裂试验,并结合高精度三维激光扫描技术,获得了岩样拉伸力学参数和破裂面线粗糙度、盒维数随层理倾角的变化规律。研究结果表明：随着层理倾角的增加,灰岩抗拉强度与拉伸模量逐渐降低;张拉裂缝呈现出基体拉裂-拉剪复合-弱面层理张拉的破裂变化趋势;且最终破坏形态可分为直线型、月牙形与弧形;破裂面线粗糙度与盒维数值随层理倾角增加而先增大、后减小、再增大,起伏粗糙度与破裂面张拉作用大小呈正相关、与破裂面剪切作用大小呈负相关关系。研究结果可为进一步完善层状岩体张拉破坏内部演化机制研究提供参考。     

层状类岩体室内制样方法及单轴压缩力学机理研究

为了更好的开展层状岩体室内试验研究,结合现有层状岩体模拟试验试样制作方法的优点,提出一种新的制样方法。以环氧树脂类胶凝材料为粘结剂,通过浇筑、拼装、粘贴、切割、打磨、成型等工序,制作出基岩和层理力学特性均可控的层状类岩体试样。通过开展不同层理倾角下层状岩体单轴压缩试验,所获取的层状类岩体试样的弹性模量和峰值强度都随着层理倾角的增大而呈现先降低后增大的Ｕ型变化规律,符合实际天然层状岩体的变形和强度特征。     

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.     

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.     

浅谈天湖水电站水轮机运行故障及处理措施

简述天湖水电站投运以来各种故障的表现形式，分析其原因，提出了相应的处理方法及措施，并对合理利用国内外设备提出建议。