苏家湾隧道初期支护变形侵限处理措施及施工工艺的研究

文章针对苏家湾隧道发生的初期支护变形侵限的病害,通过对隧道洞身地质条件的分析,并利用有限元软件MIDAS-GTS对隧道初期支护结构及二次衬砌进行了验算,确定出控制隧道初期支护变形的支护参数;并提出施工前加强对隧道中线顶部地表的地形地貌调查,完善排水系统、隧道内加强支护系统、适当加大预留变形量,并加强监控量测等施工工艺和处理措施。     

乌鞘岭特长隧道软弱围岩大变形特性研究

乌鞘岭特长隧道全长20050m,是我国目前正在修建的国内最长的单线铁路隧道.隧道施工中发生了严重的围岩大变形,主要表现为隧道中部岭脊地段F4～F7断层构成的"挤压构造带"在深埋高地应力条件下的软弱围岩大变形,拱顶最大下沉及侧壁最大水平收敛变形量均达1000mm以上,导致初期支护开裂破坏并严重侵入衬砌净空等,不得不将初期支护全部或部分拆除重做,再施作二次衬砌.文章对隧道区域工程地质环境、软弱围岩变形力学特性及初期支护破坏规律、围岩变形的影响因素等进行了分析研究,并讨论了隧道围岩加固、初期支护预留变形量与二次衬砌施作时机等问题.     

公路隧道穿越软弱围岩的变形与控制方法

公路隧道穿越软弱围岩时,其施工难点往往是如何将围岩变形、初期支护拱顶下沉和水平收敛位移控制在允许范围内,处理不当将造成结构开裂、变形以及初期支护侵入二次衬砌甚至坍方等病害.从国内施工现状与存在的问题入手,分析了引起隧道大变形的原因,总结出控制隧道大变形的两大关键点:一是选择合适的施工方法,二是要采取有效控制沉降的措施.并重点针对拱部核心土台阶法提出了控制沉降的措施,包括施工原则贯彻始终、横断面开挖合理分步、控制施工进尺及台阶长度、施作锁脚锚杆和垫块、合理处理渗水和施工用水、减少地基扰动、清除虚碴、加强施工动态管理等几个方面.     

崇遵高速公路凉风垭隧道严重变形分析

文章从地质构造、设计和施工等方面分析了造成软弱破碎围岩隧道初期支护严重变形的原因,用渐近线和双曲正切函数推导测点最终位移量和各阶段位移速率,研究变形隧道的开挖及支护对策,并探讨了提前施作二次衬砌的必要性.     

工程措施对控制大跨度海底隧道结构变形的施工效果研究

厦门东通道翔安隧道是我国第一条海底隧道,隧道场区地质条件复杂.施工难度大.施工至今,多个区段的隧道结构变形都超过了预留变形量,为此施工单位采取了多种工程措施,有效地抑制了隧道的结构变形.文章首先基于厦门海底隧道的现场监测数据,分析了隧道结构发生异常变形的原因;然后通过数值模拟结果与实测数据的对比,研究了各工程措施在此类地质条件下的施工效果.研究认为:在施工过程中,采用锁脚锚管、仰拱注浆及井点降水可以有效地抑制初期支护变形,尤其是对洞内及地表同时进行井点降水时,隧道拱顶下沉量可以减小约50%,拱部塑性区范围也大幅度减小;变更临时支护结构参数和采用系统锚杆对控制隧道结构变形也有一定的作用,但是在此类地质条件下其效用不明显;另外,隧道断面的封闭时间和封闭距离对其结构变形影响很大,应尽快施作仰拱,使断面尽早封闭成环.     

乌鞘岭特长隧道围岩监控量测设计与应用

文章重点介绍了以监控隧道稳定性为目的的围岩监控量测在乌鞘岭隧道工程中的应用.通过监控围岩和支护状态,并对量测数据进行分析,来调整支护参数及最大预留变形量,确定仰拱、二次衬砌的合理施作时间,制定相关施工方案和措施,判定施工方法是否有效,并根据实施效果作出评价.     

乌鞘岭隧道F7断层施工监测与断层活动及隧道变形特性分析

乌鞘岭隧道F7断层长达817m,埋深340～600m,在施工中初期支护发生了连续大变形并被破坏,先后多次调整施工方案并加强了施工量测和结构压力、应力监测.文章介绍了该隧道监控量测的方法和结果,分析了F7断层活动特性和对施工的影响以及隧道围岩、初期支护、二次衬砌等变形特征,并针对大地应力及活动软弱围岩隧道的施工提出了几点建议.     

鹧鸪山隧道二次衬砌开裂机理及支护时机探讨

隧道二次衬砌开裂成因复杂,只有分清隧道二次衬砌开裂原因,才能对其提出合理的处治对策,以保证隧道施工、运营安全。文章以某高速公路(炭质)千枚岩隧道为例,基于隧道出口段二次衬砌开裂特征,结合现场监控量测以及工程地质条件,分析该隧道二次衬砌开裂主要原因是围岩地质条件差、围岩级别低且二次衬砌施作过早。然后进一步采用数值计算分析不同二次衬砌施作时机下的应力特征,结果表明:二次衬砌施作过早导致边墙和拱腰附近二次衬砌内侧产生较大的拉应力,且二次衬砌施作越早,拉应力越大,这将导致二次衬砌张拉开裂;在初期支护变形量为隧道最终变形收敛值的65%~70%之后施作二次衬砌较适宜。建议在类似隧道施工中加强监控量测,严格控制二次衬砌支护时机。     

某高速公路隧道严重变形分析及处理

本文从地质构造、设计和施工等因素分析造成软弱破碎围岩隧道初期支护严重变形的原因，用渐近线和双曲正切函数推导测点最终位移量和各阶段位移速率，研究变形隧道的开挖及支护对策，探讨提前施作二次衬砌的充分必要性。     

全站仪在软弱围岩初期支护变形量测中的应用

通过分析软弱围岩隧道初期支护的变形特点以及传统量测方法的局限性,提出了应用全站仪进行隧道支护变形量测的新方法,并进行了精度分析.通过理论分析和在某隧道变形量测中的实际应用,表明利用全站仪进行软弱围岩隧道初期支护的变形量测可以克服施工干扰,提高作业效率.     

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.     

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。     

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.     

Real-world gaseous and particle emissions of a Bi-fuel gasoline/CNG Euro 6 passenger car

The objective of the present study is the assessment of the environmental impact of a bivalent (bi-fuel) vehicle, running either on gasoline or compressed natural gas (CNG). To that aim, a Euro 6 passenger car was tested under various real-world driving conditions. In order to cover the full range of conventional powertrains currently in the market, the tests were also repeated on a Euro 6 diesel passenger car. Both cars were driven in two routes, the first complying with the regulation limits and the second going beyond them. Carbon monoxide (CO), nitrogen oxides (NO_x) and particle number (PN) emissions were recorded using a Portable Emissions Measurement System (PEMS). Apart from the aggregated emission levels, in g/km, the exact emission location along the route was also assessed. Natural gas proved beneficial for CO and PN emissions, the level of which always remained below the respective legislation limits. On the other hand, under the dynamic driving conditions with gasoline, the relevant limits were exceeded. Cold start, occurring at the beginning of the urban part, and motorway driving were identified as major contributors to total emissions, especially in gasoline mode. However, the application of natural gas was associated with a penalty in NO_x emissions, which were significantly increased as compared to gasoline. Local peaks within the urban part were identified in CNG mode. In any case, the diesel vehicle was by far the highest NO_x emitter.     

Seaport performance analysis using robust non-parametric efficiency estimators

Abstract

Seaport services have been developing year on year, playing an increasingly important role in the economy and the transportation markets of each country. This increases interest in measuring their performance. This paper evaluates the performance of a set of European seaports by means of robust non-parametric approaches. Using order-m and bootstrap procedures, the major problems of traditional data envelopment analysis and free disposal hull methods – concerning noise, presence of outliers and the ‘curse of dimensionality’ – are overcome. With this study considerable levels of inefficiency were found in the European seaports sector.     

Bicycle parking: a systematic review of scientific literature on parking behaviour,parking preferences,and their influence on cycling and travel behaviour

ABSTRACT

Cycling is experiencing a revival in many cities. Research has focused on the determinants of cycling – in particular the role of the built environment and road infrastructure. Bicycle parking has received little attention – even though bicycles are parked most of the time. This article reviews the scientific literature on bicycle parking and identifies existing gaps in research and knowledge. The review analyses 94 peer-reviewed papers identified through a search in Scopus and Web of Science, in December 2017. The annual number of papers increased 15-fold between 1995 and 2017. Overall, the level of evidence on the importance of bicycle parking is limited. The majority of studies are based on cross-sectional data with the presence of parking as a binary independent variable. Most studies focus on bicycle parking at public transport stops and at work places. Few studies report on bicycle parking throughout cities, and hardly any on parking at residential locations. Bicycle parking supply and quality appears to be a determinant of cycling for current and potential cyclists. Our findings can serve as input for an evidence-based debate on the role of bicycle parking. For practitioners, our research supports investment in bicycle parking, but acknowledges that a proper evaluation of such initiatives needs to be conducted to increase the level of evidence.     

Multilevel analysis of daily time use and time allocation to activity types accounting for complex covariance structures using correlated random effects

In this paper multilevel analysis is used to study individual choices of time allocation to maintenance, subsistence, leisure, and travel time exploiting the nested data hierarchy of households, persons, and occasions of measurement. The multilevel models in this paper examine the joint and multivariate correlation structure of four dependent variables in a cross-sectional and longitudinal way. In this way, observed and unobserved heterogeneity are estimated using random effects at the household, person, and temporal levels. In addition, random coefficients associated with explanatory variables are also estimated and correlated with these random effects. Using the wide spectrum of options offered by multilevel models to account for individual and group heterogeneity, complex interdependencies among individuals within their households, within themselves over time, and within themselves but across different indicators of behavior, are analyzed. Findings in this analysis include large variance contribution by each level considered, clear evidence of non-linear dynamic behavior in time-allocation, different trajectories of change in time allocation for each of the four dependent variables used, and lack of symmetry in change over time characterized by different trajectories in the longitudinal evolution of each dependent variable. In addition, the multivariate correlation structure among the four dependent variables is different at each of the three levels of analysis.     

从"神经末梢"到"国际枢纽"——十六大以来广西交通发展综述

文章总结了党的十六大以来广西交通发展取得的成绩,指出广西交通正在从"神经末梢"发展为"国际枢纽",为广西经济社会发展提供了重要支撑。     

Increasing urban tram system efficiency,with battery storage and electric vehicle charging

This paper examines the possible placement of Energy Storage Systems (ESS) on an urban tram system for the purpose of exploring potential increases in operating efficiency through the examination of different locations for battery energy storage. Further, the paper suggests the utilisation of Electric Vehicle (EV) batteries at existing Park and Ride (P&R) sites as a means of achieving additional energy storage at these locations. The study achieves this through MATLAB modelling utilising captured GPS data and publically available information. This study examines the scenario of uni-directional substations with no interconnection between the overhead catenary for both directions of travel, and discusses the trade-offs between ESS size and required current limits.The results show the savings in both energy and basic CO₂ emissions alongside the discussion of Return on Investment (RoI) that can be achieved through the potential installation of ESS at identified ideal locations along the tram network. Moreover, this may be extended to the use of EVs as stationary ESS sited at the existing P&R facilities. Further, the model may also be used to inform future infrastructure upgrades and potential improvements to air quality within urban environments.