浅埋偏压双侧近接隧道影响分区及对策研究

新建隧道施工会引起围岩应力重分布,从而对邻近既有隧道产生较大的影响。文章依托浦梅铁路新建武调1号隧道和武调隧道双侧近接向莆铁路既有武调隧道工程,采用理论研究的方法建立了适用于双侧近接既有隧道影响度的表达式,得到了基于结构位移准则和结构可靠度准则的两种近接影响分区。通过数值模拟、回归计算的方法完成了两种双侧近接影响分区,结果表明:相比基于结构可靠度准则的近接影响分区,基于结构位移准则的近接影响分区方法中强影响区范围较小,弱影响区范围较大。对处于不同影响分区的既有隧道、新建隧道、中间土体提出了对应的适用于依托工程的施工对策。在不同影响分区范围内,对既有隧道结构位移、衬砌应力进行监测。监测结果显示:当采取既定的施工对策后,既有隧道结构位移、衬砌应力均得到了很好的控制,既有隧道受左侧新建偏压隧道的影响大于右侧新建隧道。     

城区近距离多孔隧道施工关键技术研究

文章以广州地铁5、6号线区庄换乘地铁车站交叠段近接4孔隧道施工为背景,分析了近接隧道施工过程中地层应力重分布特性,对近接隧道施工中先后施工隧道间的围岩稳定性、隧道支护结构的内力、变形相互影响进行了分析研究,提出了相应的施工安全控制指标;对4孔近接隧道施工中的关键施工力学问题进行了三维模拟计算分析,提出了合理的4孔近接隧道同时施工关键技术方案。研究结果表明,在该地层条件下只要采取合理的地层加固措施和隧道支护方案,合理控制平行近接隧道、空间交叠隧道间的错距,则多孔近接隧道同时施工方案是可行和安全的。     

地铁区间盾构隧道对周边建筑物结构基础影响分析

针对区间新建隧道近接既有桩基的地铁工程,进行了三维有限元数值模拟的施工力学行为研究.研究结果表明与无桩情况相比较,近接桩基施工将引起新建隧道自身结构,特别是与既有桩基近接一侧边墙,不利的受力特征,并且近接施工还将引起既有桩基产生偏向隧道水平方向的"拉伸"变形情况.因此,需要采取加固措施,以确保隧道自身结构以及近接地下建筑物的安全.此外,考察不同刚度折减系数时,发现桩基水平侧向变形几乎没有变化,这表明改变盾构管片的拼装方式,在整体上对近接地下建筑物几乎无影响.     

"盖挖法"在近接既有建筑物的大跨隧道施工中的应用

针对大跨隧道洞口段埋深浅、邻近既有建筑物的工程特点,在国内外研究成果的基础上,对近接施工影响程度及范围进行了分析,并对各施工方案进行详细比选.结果表明,"盖挖法"不但能克服传统方法带来的各种不利因素,而且能够确保隧道的施工进度和既有建筑物的安全,同时可减少对洞口生态环境的破坏,是最佳的近接施工方案.     

泥岩地层盾构隧道下穿既有成昆铁路无预加固施工安全分析

新建地铁隧道下穿既有运营铁路时,如何在无预加固措施下保证新建隧道和既有铁路的安全,是施工的关键。文章依托成都轨道交通9号线一期工程元华停车场东出入场线盾构隧道近接既有成昆铁路工程,采用有限元软件模拟最不利工况下的工程安全性,通过主动托换补偿地层应力损失的可行性以及岩土物理力学参数变化的敏感性。研究结果表明,在泥岩地层、无预加固、有列车荷载作用、注浆压力控制在0.30 MPa及以上条件下,盾构隧道近接下穿既有成昆铁路施工时,能主动托换补偿地层应力损失,限制围岩塑性区发展,满足铁路线路轨道10m弦高低偏差矢度值≤±0.5 mm的管理规定,确保盾构近接施工时的安全。     

泥质粉砂岩地层中后行盾构隧道近接施工对大断面矿山法隧道的影响研究

两条以上隧道近距离施工时,将导致既有隧道与新建隧道结构的受力变化,带来工法、工序与施工对策优化等问题。文章以长沙轨道交通3号线盾构隧道近接大断面矿山法隧道施工为工程依托,针对泥质粉砂岩地层,采用数值模拟和模型试验的手段,研究盾构隧道近接矿山法隧道施工的影响规律,并基于地表沉降准则提出影响分区。研究表明:盾构法隧道施工中,盾构开挖距离研究断面1倍洞径至研究断面完成管片拼装这一过程,是引起对应地表沉降增加及既有矿山法结构附加位移增长的主要阶段;对矿山法隧道结构的影响以竖向附加变形为主,具体表现为矿山法隧道整体上浮,越靠近盾构隧道的结构受影响越大;内力影响表现为矿山法隧道结构内力不均匀变化,靠近盾构隧道一侧结构受压加强,远离盾构隧道一侧结构易发生受拉破坏。     

桥梁施工对既有铁路隧道的影响研究

为最大限度地规避新建桥梁对既有铁路隧道的影响,以桥梁施工对既有铁路隧道造成的潜在风险为切入点,总结桥梁施工对既有铁路隧道造成影响的评估方法,分析桥梁施工对既有铁路隧道的安全影响因素,进而提出相关措施,希望对同行工作有所助益。     

基坑群开挖对近接运营地铁隧道隆沉变形的影响研究

文章以深圳地铁车公庙枢纽工程为例,研究了受基坑群开挖影响的近接运营地铁隧道的隆沉变形规律及其变位控制措施。为了达到控制既有隧道及轨道结构变位的目的,通过方案优化、理论分析和数值模拟等研究手段,根据结构变位分配原理,制定了基坑群施工各步序轨道结构的变形控制标准。受基坑开挖卸载效应的影响,近接既有隧道具有明显的变位叠加效应,其中基坑开挖卸载和降水是影响结构变形控制的关键步序。基坑降水对控制下卧隧道隆起变形是有利因素,但紧邻侧方位基坑降水对控制结构水平变形是不利因素,因此在设计和施工中应综合考虑地下结构不同方向变位基准来制定合理的降水措施。实测结果表明,基坑群开挖过程中既有地铁轨道结构变形满足控制标准要求,验证了变形控制基准的合理性和工程措施的有效性。     

卵石地层地铁隧道近接施工位移特征研究

以北京地铁9号线某区间隧道近接既有铁路桥梁施工为背景,文章基于Hardening-soiJ本构模型采用三维数值计算与现场实测结果相对比的方式,研究卵石地层地铁隧道近接既有铁路桥施工的位移特征。研究得出的结论为:(1)卵石地层岩体较为松散,胶结性较差,围岩稳定性较低,可引入Hardening-soil模型模拟其应力-应变关系;(2)区间隧道开挖引发的竖向位移主要集中在隧道拱顶部位,并随着向地层深部的发展逐渐衰减;(3)地铁区间隧道施工引发的地表沉降可认为是两条单洞隧道地表沉降曲线的叠加,现场实测与数值计算得出的规律一致;(4)既有铁路桥结构最大位移值小于《铁路线路修理规则》的容许位移,现有开挖方式和支护参数满足既有结构安全运营条件;(5)地铁区间隧道开挖引发的地层、既有桥梁结构水平位移整体较小;(6)区间隧道开挖引起的土体扰动主要集中在隧道洞周5.4 m范围内。     

近邻隧道爆破施工相互动力影响研究

当两隧道距离较近时,新建隧道爆破施工可能导致既有隧道围岩与衬砌结构的变形甚至损坏。文章以某典型大跨公路隧道近接一小型既有隧道工程为背景,采用LS-DYNA显式动力数值模拟方法,开展近距离隧道爆破施工的相互影响研究。结果表明:新建隧道内振速分量均出现在垂直隧道轮廓线方向,既有隧道迎爆侧振速水平分量最大;围岩类型对爆破振动速度的影响主要在新建隧道近既有隧道侧,对既有隧道内振速影响较小;药量和跨度对新建隧道爆源近区底板影响较大,净距对新建隧道近既有隧道侧影响较大;药量增大、净距减小、跨度减小均会在一定程度上引起既有隧道内振速的增大;相对位置不同,新建隧道最大振速均出现在近既有隧道侧,既有隧道均出现在迎爆侧,爆破掌子面从既有隧道上方穿越时引起的振动大于远离时;既有隧道对新建隧道内的振速具有一定的放大效应。     

The impact of outcome framing and psychological distance of air pollution consequences on transportation mode choice

Recent years, air pollution phenomenon has become one of the crucial problems of Tehran, Iran. Due to main political and economic role of Tehran, population of this metropolis is high and increasing. Urban transportation of this highly populated city contributes more than 70% of air pollution problem in this city. Although a number of urban transport developments, policy measures and regulations have been employed, Tehran’s air pollution has remained crucial thus far. Finding ways to encourage individuals to behave more sustainable can be considered as a substantial approach of tackling environmental problems such as air pollution, since it can be highly cost-effective and fast. This research attempt to evaluate the impacts of two factors of outcome framing and psychological distance of air pollution on citizen’s willingness to behave environmental friendly, particularly to change the travel mode choice. Results illustrate that communicating the consequences of air pollution can provoke individuals’ to act more environment friendly or in particular to change their intention for using more sustainable mode of transportation. Framing the positive consequences of mitigating air pollution take precedence over framing the negative consequences. Moreover the gains of mitigating air pollution have an impact on the willingness to use of bicycle and bus. Results also show that decreasing the psychological distance of air pollution in order to make manipulated frame more personally relevant has no significant impact on respondents.     

Planning the driverless city

ABSTRACT

AV technologies have the potential to transform urban landscapes and existing transport systems and networks. Yet, the utopian imaginary of reduced automobile ownership and a new shared economic future sits in tension with suggestions that car dependency, urban sprawl and transport inaccessibility will be exacerbated. The issues are situated in a complex governance landscape involving an influential private sector who are increasingly setting the agenda. The public sector may be forced into reacting to the new innovations by information technology and automobile companies as they are introduced into existing built environments. Drawing on an extensive literature base and interviews with public sector planners, this paper reveals the conceptual gaps in the framing of AV technology – the prospects and limits – and how these are conceived. The paper raises questions about the role urban planning can play in the rollout of AVs in order to anticipate and mediate unwanted built environment and socio-spatial impacts, as well as reconciling the ambition of transport innovation with the public purpose of planning.     

The employee mobility budget: Aligning sustainable transportation with human resource management?

This paper discusses how a particular tool in the employment relationship has become part of a desirable transport future. We examine how and why the employee mobility budget has entered the set of sustainable transport measures in Belgium. In a discourse analysis, we examined 52 articles from newspapers, magazines as well as research reports. The main actors in the debate are identified using an exploratory social network analysis, and we discuss the various definitions of the employee mobility budget, the framing of the problems to be solved (in the first place congestion), and the main conflicts between actors. The results reveal the sustained efforts to put the idea on the agenda and the formation of a coalition of the willing. The fact that the mobility budget concept is highly compatible with the hegemonic discourse on employment relations contributes to its popularity. Finally, the individualisation of employment relations and the decrease in attention for environmental aspects are highlighted as potential threats of the type of sustainable mobility policy studied in this paper.     

Assessing communicative rationality as a transportation planning paradigm

Communicative rationality offers a new paradigm for transportation planning. Drawing on the literature and lessons from transportation planning practice, this paper describes the characteristics of a “communicative” form of transportation planning and compares them with conventional practices. A communicative rationality paradigm would place language and discourse at the core of transportation planning. The paper argues that it would lead to greater attention to desired transportation ends (goals), better integration of means and ends, new forms of participation and learning, and enhanced deliberative capacity. The paper explains the implications of this paradigm for the role of the transportation planner, the purpose of planning, the planning process, communicative practices, problem framing, and the nature of planning analysis. The paper concludes with an assessment of communicative rationality's ability to promote more effective transportation planning. It seeks to create a dialogue that will support the investigation of new transportation planning processes. This revised version was published online in June 2006 with corrections to the Cover Date.     

沉管隧道二次围堰施工技术

沉管隧道二次围堰施工效果的好坏将直接影响到岸上主体结构施工时基坑的安全,关系到沉管隧道施工的工期、成本.文章简要介绍了沉管隧道二次围堰水下不分散混凝土施工技术.     

基于神经网络的无信号路口人车交通行为预测分析

以无信号灯路口人车交通行为为研究对象,对行人和机动车辆在无信号灯路口的整体交通行为进行分类预测。在对路口现场交通情况进行拍摄后,用电脑的分帧技术对所需要的数据进行提取和分类,而后建立BP神经网络模型,确定神经网络的输入变量与输出变量。将样本数据导入神经网络并进行训练和测试后,得出行人和车辆过街类型的分类准确率,并且通过准确率所达到的标准来证明了BP神经网络模型的可行性。     

The statistical analysis of crash-frequency data: A review and assessment of methodological alternatives

Gaining a better understanding of the factors that affect the likelihood of a vehicle crash has been an area of research focus for many decades. However, in the absence of detailed driving data that would help improve the identification of cause and effect relationships with individual vehicle crashes, most researchers have addressed this problem by framing it in terms of understanding the factors that affect the frequency of crashes – the number of crashes occurring in some geographical space (usually a roadway segment or intersection) over some specified time period. This paper provides a detailed review of the key issues associated with crash-frequency data as well as the strengths and weaknesses of the various methodological approaches that researchers have used to address these problems. While the steady march of methodological innovation (including recent applications of random parameter and finite mixture models) has substantially improved our understanding of the factors that affect crash-frequencies, it is the prospect of combining evolving methodologies with far more detailed vehicle crash data that holds the greatest promise for the future.     

广西百色华村特大桥主桥上构施工方法

文章介绍了广西百色华村特大桥在高墩搭设支架施工的情况下,采用索道安装挂篮运输施工材料等施工方法,为该桥梁建设降低施工成本、加快施工进度,确保施工安全打下了良好的基础,同时为陡峭复杂的山区地形及深水区更大跨度的桥梁施工提供参考与借鉴。     

蒲庙大桥吊杆更换施工监控研究

拱桥吊杆施工质量的好坏直接影响到施工安全乃至桥梁营运的安全,而施工监控对提高施工质量、施工安全起重要作用,吊杆更换成功与否很大程度上取决于施工监控。文章以南宁市蒲庙大桥的维修加固为例,介绍了吊杆更换监控测试的方法,为大桥吊杆更换施工监控提供参考。     

Contrasts between utility maximisation and regret minimisation in the presence of opt out alternatives

An increasing number of studies of choice behaviour are looking at Random Regret Minimisation (RRM) as an alternative to the well established Random Utility Maximisation (RUM) framework. Empirical evidence tends to show small differences in performance between the two approaches, with the implied preference between the models being dataset specific. In the present paper, we discuss how in the context of choice tasks involving an opt out alternative, the differences are potentially more clear cut. Specifically, we hypothesise that when opt out alternatives are framed as a rejection of all the available alternatives, this is likely to have a detrimental impact on the performance of RRM, while the performance of RUM suffers more than RRM when the opt out is framed as a respondent being indifferent between the alternatives on offer. We provide empirical support for these hypotheses through two case studies, using the two different types of opt out alternatives. Our findings suggest that analysts need to carefully evaluate their choice of model structure in the presence of opt out alternatives, while any a priori preference for a given model structure should be taken into account in survey framing.