厦门翔安海底隧道CRD法中各施工部对拱顶下沉的影响分析

文章以厦门翔安海底隧道陆域段软弱地层大断面浅埋隧道CRD法施工为工程背景,结合现场位移监控量测和实际施工情况,对不同开挖顺序下CRD法中各施工部对拱顶下沉的影响进行了分析研究。研究结果表明,翔安隧道CRD法拱顶下沉为台阶状上升曲线,最后趋于稳定;各分部开挖引起的拱顶下沉量具有一定的比例关系,可用于对最终拱顶下沉量的预报和控制指示;各分部仰拱及时闭合是控制最终下沉量的关键;采用CRD1、3部超前施工比CRD1、2部超前对控制拱顶下沉较为有利;施工中应重点监测和控制最早开挖的CRD1部拱顶下沉。     

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.     

大断面浅埋偏压隧道CRD法施工工序研究

文章以良村隧道CRD法施工为工程背景,布设了变形监测点及内力测试元件,分析了CRD法施工隧道围岩变形情况及结构内力特征,并对CRD法施工隧道在不同开挖顺序下的开挖过程进行了数值模拟,分析比较了不同开挖顺序时的围岩位移、应力变化情况。结果表明:CRD法对各分部施工工序影响较大,且各分部对拱顶下沉的影响程度从大至小依次为1部、2部、3部和4部;隧道内侧围岩压力大于外侧,钢支撑内力均为压应力,且拱腰位置轴力大于其它部位。比较隧道开挖变形的差异以及结构的受力特点,结合数值分析结果,得出了山体外侧先开挖方案无论在围岩变形还是隧道结构受力方面相比于山体外侧后开挖都较小,安全系数相对较高。因此,合理的施工工序应该是先进行山体外侧开挖并施作初期支护,然后再在山体内侧开挖施工。     

大断面海底隧道在不同施工工法下的力学行为研究

厦门海底隧道是我国第一条海底隧道,其地质条件差,地下水丰富,施工过程中支护结构常发生较大的变形。为了保证施工安全,寻求一套合理的控制措施用以抑制异常变形是至关重要的。文章以厦门海底隧道工程陆域段为实例,运用现场监测和数值模拟两种手段,对在围岩条件基本相同时采用CRD、双侧壁导坑及CD法开挖引起的支护结构位移和安全性进行了对比研究。     

浅埋软弱围岩隧道变形特征研究

软弱围岩隧道受开挖扰动影响变形明显,施工中若稍有不慎,就会导致隧道塌方。文章以厦门莲岳隧道A匝道隧道为工程背景,结合隧道所处地质条件,采用数值模拟和现场监测相结合的方法,对浅埋软弱围岩隧道变形特征进行了研究。结果表明,对于软弱围岩隧道,不论是全断面开挖还是台阶法开挖,掌子面挤出位移最大,拱顶下沉和地表沉降次之,洞周收敛最小;隧道围岩变形可以分为掌子面前方的先行变形和掌子面后方变形,围岩条件越差,先行变形越大,约占总变形的10%~30%;采用台阶法等分部开挖工法,可减小对掌子面前方围岩的影响范围及变形。在对浅埋软弱围岩隧道的周边环境有严格变形控制要求时,要采取更为严格的预加固措施来控制隧道施工引起的围岩变形,以确保隧道施工及周边环境的安全。     

大断面黄土隧道变形规律及预留变形量研究

文章统计分析了大断面黄土隧道初期支护变形量,研究了大断面黄土隧道变形规律及预留变形量合理取值范围.大断面黄土隧道变形规律表现为:隧道拱顶、拱脚下沉差异小,隧道开挖后拱部将产生一定程度的整体下沉;隧道拱顶下沉量均大于水平收敛;初期支护封闭后,隧道周边位移基本上不再发展;当隧道埋深小于40m时,隧道变形量较大且规律不明显;当隧道埋深大于40 m时,隧道变形量分布相对集中.经过对现场量测数据的统计分析可知:在Ⅳ级围岩条件下,大断面黄土隧道预留变形量可取10～15 cm;在Ⅴ级围岩条件下,大断面黄土隧道预留变形量可取25～28 cm.     

高陡边坡下隧道洞口区稳定性研究

为研究隧道开挖工法对高陡边坡下隧道洞口区稳定性的影响,文章依托某实际隧道工程,采用FLAC3D软件建立了相应的三维模型,对三台阶法、环形预留核心土法和CRD法开挖施工进行模拟分析,并与现场监测结果进行对比,得到如下结论:(1)对比三种工法开挖时隧道围岩和边坡变形可知,CRD法为最适宜,采用该工法开挖隧道时,洞口区围岩和边坡变形最小;(2)数值模拟所得围岩及边坡变形变化规律与现场监测结果基本一致,故采用数值法进行隧道施工优化具有一定的可行性;(3)为减少隧道开挖对洞口区边坡的影响,采用CRD法进行隧道开挖,结合锚索预加固可有效提高边坡稳定性。     

铁路黄土隧道变形规律及建设管理要点研究

黄土隧道施工过程中,常出现支护破坏和隧道塌方等事故。文章基于黄土隧道工程的监控量测数据,采用统计分析方法对不同围岩级别、埋深和含水率下的黄土隧道变形规律进行了研究。结果表明:(1)Ⅳ级围岩黄土隧道拱顶下沉、周边收敛的量值分别集中在50 mm和35 mm以内,Ⅴ级围岩黄土隧道拱顶下沉、周边收敛则集中在60 mm和40 mm以内;(2)Ⅳ级、Ⅴ级围岩双线黄土隧道拱顶下沉和周边收敛变形值与含水率呈正相关关系,变形速率则先增大后减小,在含水量超过16%时变形增大明显;(3)基于拱顶沉降统计,提出Ⅳ级、Ⅴ级围岩黄土隧道设计预留变形量值范围可分别取7～9 cm和12～15 cm;(4)黄土隧道工程建设管理要点是提前梳理重难点工程,施工前严格方案审核,加强地表处理,施工时强化地质预报和监控量测,严格变更设计管理,重点做好工艺管理和施工质量控制。     

大断面海底隧道二次衬砌结构安全性评价

正在修建的厦门东通道(翔安)海底隧道是我国大陆地区第一条海底公路隧道,主隧道开挖断面达170 m~2,隧道采用钻爆法施工.在海底段穿越了几条破碎带或风化囊槽,最大水深25.7 m,风化囊槽段围岩渗透性好,水压大,隧道拱顶最大静水压力0.68 MPa,为了保证二次衬砌安全,对其进行了现场应力监测。文章通过对现场大量实测数据总结分析,研究了大断面海底隧道二次衬砌的受力特点,为相似条件下海底隧道二次衬砌的设计和施工提供了参考。     

软弱围岩大跨度隧道CRD法数值模拟分析

由于Ⅴ级围岩软弱破碎,岩土体强度低,围岩开挖后易产生松动变形,导致拱顶下沉过大、掌子面塌方等病害。文章以广东省某在建高速公路隧道为例,利用有限差分软件FLAC3D,对软弱围岩隧道采用CRD工法开挖过程中的应力、变形和塑性区的发展历程进行模拟分析。研究结果对于类似工程的设计和施工具有一定的参考价值。     

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.