大埋深、高地应力地下洞室群围岩破坏机理及应对措施研究

地下洞室开挖过程中,脆性围岩应力释放型破坏(岩爆、片帮掉块等)和结构面—应力型破坏(围岩松弛、喷层开裂、顶拱坍塌等)是洞室群围岩破坏常见的主要形式。文章以白鹤滩水电站左岸尾水连接管洞室群为研究对象,结合现场踏勘统计分析,基于500μm显微镜观察、室内岩石力学单轴压缩试验对围岩应力释放型破坏机理进行了研究,基于数值模拟、孔内摄像技术对围岩结构面—应力型破坏机理进行了研究,并分别提出了相应的应对措施。研究表明,完整性较好的脆性围岩(Ⅱ类)具有一定的塑性性能,洞室开挖卸荷后岩体易发生压剪破坏,产生与受力方向呈小夹角的破坏面,塑性势能沿破裂面释放,进而引起薄层掉块或岩爆现象;对于完整性较差的围岩(Ⅲ类),由于节理、错动带等裂隙的存在,多表现为岩性强度高、岩体强度低的性状。围岩微裂纹在高地应力作用下逐渐扩展连通,形成相互切割的结构面,并逐步向岩体深部不断发展,直至应力完全释放,受周边洞室爆破振动影响时易发生坍塌现象,破坏过程在宏观上表现为由表及里并具时效性的特点。     

特大型地下洞室群施工期通风技术研究及应用

地下洞室常采用新奥法或矿山法施工,掌子面爆破产生的污染物影响施工人员的人身安全和职业健康,同时也制约着洞室的开挖进度。文章依托白鹤滩水电站工程,提出了"三结合"、"分期设计"的地下洞室群施工期通风系统规划和设计理念,构建了三维非稳态湍流场模型,研究了复杂地下洞室群开挖期通风散烟特点和规律,提前规划并实施了与各主要洞室贯通的专用排风洞,形成了一套高效节能的"进+排"通风系统,使用变频风机在最大程度利用自然通风的基础上实现机械通风的最优效果。数值计算和现场污染物浓度测试结果表明:白鹤滩水电站地下洞室群施工期气流组织顺畅,专用排风竖井区域空气流速远大于洞室周边区域,污染物逸散路径为掌子面—排风竖井—专用排风平洞;通风15 min后,爆破产生的污染物即可全部排出洞外,效果良好。     

某地下洞室群分步开挖支护的非连续变形分析

文章分别从岩体的分步支护以及相应的收敛准则两方面对已有的非连续变形分析程序进行了改进,并应用改进的程序分析了含有随机节理的某大型水电站地下洞室群的围岩稳定问题,着重研究了施工因素的影响,突出了对分步开挖支护过程的模拟计算分析,并且通过与实际工程监测值的比较,验证了该方法的有效性。通过围岩破坏区深度和关键点的位移比较了三大洞室(主厂房,主变室,尾调室)不同的开挖顺序对围岩稳定性的影响和重点支护的关键部位,并对支护方案进行了优化。研究结果表明,此工程中先开挖主厂房与尾调室,再开挖主变室为最优开挖顺序,并且尾水调压室为洞室群支护的关键部位,可以通过在关键位置增加锚索支护的方式改善其围岩的应力状态。     

浙江温岭长屿硐天复杂钟形洞室群建模技术及稳定性分析

三维建模技术是采用Flac~(3D)进行大型不规则洞室群稳定性数值分析的关键,文章基于多软件耦合技术,综合采用AutoCAD、Surpac、Surfer、Matlab自编程序,仅依靠地形图、洞室底部中心坐标、洞室高度、洞室跨度等洞室结构主要参数,实现了复杂不规则洞室群的快速建模。同时采用16 m、8 m、4 m、2 m四种网格尺寸,对长624 m、宽480 m、高336 m且内部分布6个不规则洞室的地层模型进行了建模,在保证计算精度的前提下,2.5 h即完成了计算,大大提高了计算速度。计算与分析结果表明,本文所研究的洞室群处于稳定状态,但洞室底部围岩和中隔墙受力状态不利于稳定。为此,古人在开凿洞室过程中,采取了挖除洞室底部分围岩、在岩坑内蓄水、挖除中隔墙部分岩体等3项措施,以增强洞室结构稳定性。     

大型地下车站洞室结构设计施工技术

红旗河沟车站是重庆轻轨3号线与地铁6号线的地下换乘车站,也是当前全亚洲建设规模最大的地下暗挖车站.依托该工程,介绍了大型浅埋暗挖洞室主体结构设计方法、支护衬砌设计与施工技术,包括洞群组成、主洞与附属洞的衔接方式、埋置深度确定、主洞断面设计、高边墙式大断面主洞开挖工法、支护类型等；着重研究了十字交叉节点的结构设计方法,并采用有限元方法进行了结构受力特征分析与开挖过程施工力学计算.通过施工过程的力学分析与精细化设计,红旗河沟车站成功建成,相关设计施工方法对今后类似超大型地下洞室工程具有一定参考价值.     

大跨度洞室拱顶衬砌拱脚爆破开挖施工技术的研究

文章主要是针对由锐角、钝角与直角结构组成的复杂洞室断面,其特殊部位的控制爆破开挖方案的设计、试验与施工技术进行的分析研究.在某水电站主机洞室的钻爆法施工中,通过利用岩体钻孔线状装药爆破的特点,设计出的多向布孔、分步爆破的施工方案,有效地实施了洞室小角度复杂结构断面特殊部位的爆破开挖,解决了采用爆破技术实施复杂结构断面地下洞室爆破开挖质量难以保证的难题.     

地震动参数对地下洞室安全系数的影响分析

为解决地震作用下地下洞室围岩安全的定量评价问题,文章建立了一种基于整体安全系数和点安全系数的围岩稳定综合评判方法。首先给出了基于岩体抗剪强度折减原理的洞室整体安全系数计算方法,该方法以主厂房和主变洞之间的塑性区恰好贯通作为洞室整体失稳的临界判据,整体安全系数通过搜索折减系数而得到;然后给出了基于Mohr-Coulomb屈服准则的点安全系数计算方法。结合西南某水电站地下厂房洞室工程,研究了不同地震动输入参数对洞室整体安全系数和关键部位的点安全系数的影响规律。计算结果表明,基于安全系数的地下洞室围岩稳定定量评价方法是可行的,能够反映不同工况下洞室整体安全程度和不同部位的局部安全程度。研究发现,洞室整体安全系数和关键点安全系数均随地震波振幅、持时的增加而减小;随入射角的增加而增大;地震波低频对洞室影响较大,高频则影响较小。     

楞古水电站地下厂房围岩分级研究

围岩分级是水电工程地下洞室设计和施工重点关注的问题,因此确定合理的围岩级别对工程设计和施工具有重要意义。文章依托楞古水电站地下厂房工程,采用HC分级、[BQ]分级、Q分级和RMR分级等方法对地下洞室围岩级别进行了研究并采用回归方法对各系统分值进行了相关性分析。结果表明:对大跨度地下洞室进行围岩分级时,同时采用HC、[BQ]、Q和RMR等分级方法进行围岩级别划分,更有利于确定合理的围岩综合分级;在岩体的块度、完整性受结构面控制时,HC分级与RMR分级结果吻合度更高。     

FDS在轨道交通地下车站火灾模拟中的应用分析

火灾动力学模拟模型(FDS)是用于火灾模拟的计算软件。对该软件的建立、网格划分、计算方法进行探讨;对FDS在轨道交通地下车站火灾模拟中的应用特点进行分析,提出符合工程实际应用的计算模拟优化方法。     

锦屏二级水电站交叉隧洞模型试验研究

多洞室交叉处围岩力学状况目前国内外研究相对较少。文章以锦屏二级水电站3#引水隧洞三洞交叉段为工程背景,为了解交叉洞室对围岩的影响,进行了三维地质力学模型试验;通过两组试验,有效地揭露了交叉洞室间的相互影响,以及开挖与支护方法对围岩稳定性的影响。最后通过超载试验,确定了交叉洞室的破坏模式及其破坏过程;试验结果为指导施工提供了依据。     

Survey of R&D in PRT systems

A survey of research and development in advanced transit has been made by Chalmers University of Technology in Gothenburg in cooperation with Trans21 in Boston. Summary findings are reported for fourteen academic research programs and ten development programs for PRT. An earlier version of this paper was presented at the International Conference of PRT and other Emerging Systems held in Minneapolis in 1996.     

The Impact of Container Type Diversification on Regional British Port Development Strategies

Abstract

Despite a concentration of container traffic in the southeast of the UK over the last few decades, regional ports are attempting new development strategies to capture or retain specific traffic segments. These include intra-European short-sea traffic and a potentially increasing feeder market. These trends are reflected in the movement of different container types, which result in a number of planning challenges related to changing infrastructural and operational requirements. This paper uses highly disaggregated data on container type movements to address three issues that can inform these planning challenges. First, the imbalance of trade resulting in empty container repositioning; second, the requirement for gauge-cleared rail routes to cater for the increasing proportion of high-cube containers; and third, the specialisation of European short-sea traffic at secondary UK ports. The results reveal the disproportionate repositioning of empty containers at Scottish ports and the importance of 45?ft, high-cube and pallet-wide containers at regional ports, highlighting their focus on intra-European short-sea traffic and raising difficulties relating to their lower quality of landside infrastructure (particularly rail) in comparison to the large south-eastern ports. The potential repercussions on hinterland infrastructure development raise questions about both public and private sector responses to regional port development.     

Modular route bus design – A method of meeting transport operation and vehicle manufacturing requirements

This research examines the problem of route bus specification and vehicle manufacturability. In order for bus operators to provide transport services, a range of vehicle configurations must be available from bus manufacturers, generating variety which has a negative impact on the manufacturing process. Larger part inventories, uncontrolled labour tasks and more troublesome maintenance are known impacts of this variety. This research identifies the functional necessities in route bus interior design and reduces the problems in bus manufacture and operation caused by specification diversity by proposing a modularised system of bus design. In particular, it makes recommendations as to how bus configuration should be carried out, ensuring an optimum mix of operational and manufacturing needs:

• 1.Determine user needs before the bus specification process.
• 2.Designs to be developed by the manufacturer in response to user needs.
• 3.This design should be standardised where possible, as suggested by the user needs.
• 4.Where user needs dictate product variations, apply a mass customisation approach to accommodate these needs.

The recommendations are communicated in design proposals for a modular bus interior, demonstrated by four cases designed to meet the present status quo of bus interior design and predictions for the future of the field.     

Optimization of bus stop locations for improving transit accessibility

A mathematical model is developed in this paper to improve the accessibility of a bus service. To formulate the optimization model, a segment of a bus route is given, on which a number of demand entry points are distributed realistically. The objective total cost function (i.e. the sum of supplier and user costs) is minimized by optimizing the number and locations of stops, subject to non‐additive users' value of time. A numerical example is designed to demonstrate the effectiveness of the method thus developed to optimize the bus stop location problem. The sensitivity of the total cost to various parameters (e.g. value of users' time, access speed, and demand density) and the effect of the parameters on the optimal stop locations are analyzed and discussed.     

Productive efficiency and ownership of urban bus services

The established ownership mix of urban bus operations in Australia provides a unique opportunity to investigate the productivity differences between public and private bus service supply. Using duality theory in economics which links economic indices of factor productivity to the cost structure of a firm, we develop empirical measures of total and partial productivity of inputs, and adjust the differences for the effects of ownership status and operating environment. The evidence supports the notion that private supply of public passenger transport in general has performed more efficiently in the past than public supply, although the differences in productivity need not continue in the future.     

管道风险分析指数评分法中分值调整初探

管道风险分析指数评分法中重要步骤之一就是确定影响管道事故因素的权重,各个管道风险因素在整个管道事故中所占的权重是不相同的。针对目前管道风险分析指数评分法基本假设之一（各因素的分值范围都是0～100分）,为了更加客观、准确、合理地反映各个风险因素对于管道事故的影响程度,提出并论述了依据层次分析法的数学逻辑性进行综合计算得出管道风险因素的权重,然后对评分法中各个因素的最高分值,根据其权重不同进行相应调整,从而增强评价者对风险因素的认识和评判能力,提高管道风险评价结果的准确性。     

Determinants of modal choice in freight transport

In the next few years, exciting developments in the field of freight transport are likely to occur. The Channel Tunnel will be perceived as giving railways much greater distance of operation, compared to the current train ferry to/from Great Britain. The further development of swap-body technology will allow easier modal transfer and the creation, in 1992, of a single market in Europe will transform the pattern of trade. All of these are likely to have significant impacts on modal choice, and hence modal split, in freight transport. Reappraisal by many firms of the modes of transport used is likely but will it result in a net transfer of freight from road to rail and, if so, to what extent? To answer such questions, an accurate and reliable method of predicting modal split is required. Research in the past has concentrated on the development of modal split models based on generalised costs. These fail to explain adequately the prevalence of road freight in the UK. From surveys of freight managers within industry, it is clear that models to date rely too heavily on the economic cost factor and too little on behavioural factors (Jeffs 1985). This paper derives from a recent study of freight transport modal choice from the standpoint of the transport decision-maker within the firm. It attempts to shed light on the actual parameters which should be incorporated into a modal split model. Many variables appear to exert an influence on modal choice decision-making process. However, it is possible to categorise them into six main groups, namely: customer-requirements; product-characteristics; company structure/organisation; government interventions; available transport facilities; and perceptions of the decision-maker him/herself. It is the interactions and inter-relationships between these which ultimately determine freight modal split. This study has shown that the relationship between the outcome of the transport decision process and the values of particular determinants of modal split is not straight-forward, due to the complexity and variety of interactions involved. Perhaps one of the main reasons for researchers' failure hitherto to develop a successful modal-split model has been the preoccupation with techniques that rely on the development of common metric (e.g. generalised cost), which has led to the exclusion of some important explanatory variables along quite different dimensions. Another important issue concerns the appropriate level of aggregation. In order not to reduce the explanatory power of the key variables, it is important to work at a disaggregate level, although this does make substantial demands on data. The use of factor analysis enables both the aggregation of information without loss of behavioural reality and the specification of variables in terms of a common metric. In conclusion, freight transport has usually been examined within too narrow a framework. It must be placed firmly within the context of the total industrial process. The demand for freight transport is directly influenced by the level, composition and geographical distribution of production and consumption activities. Freight flows are complex and so it is highly unlikely that a universal mode-choice model can ever be developed. Future research should, therefore, be directed towards developing partial models in response to specific needs of those involved in decision-taking in the freight sector.     

A century of evolution of the accessibility concept

The concept of accessibility has acquired numerous meanings along multiple dimensions during the century of its evolution. This essay argues for the salience of two dimensions: application-based and definition-based. In its application, accessibility has incorporated positive and normative dimensions which have varied in prominence over time. In its definition, accessibility has varied between a mode of evaluation incorporating measured mobility and proximity, on the one hand, and a predefined market basket of urbanist improvements to transportation and land use systems, on the other. Advocates of the accessibility shift should emphasize both the measured approach to accessibility and accessibility’s normative side.     

天然气站往复式压缩机活塞失效分析

针对天然气站往复式压缩机活塞的断裂事故,运用失效分析方法,开展了活塞断口扫描电镜分析、能谱和金相分析。根据断口形貌的电镜和金相观察结果,结合理论知识,分析确定了该活塞发生断裂事故的主要原因,即在特定工况下该活塞的材料缺陷是造成断裂的主要因素。