盾构法与矿山法相结合施工技术

深圳地铁一期工程益田～香蜜湖区间隧道,采用盾构法与矿山法相结合的施工技术,既缩短了工期、降低了工程成本,又维持正常交通,保护了沿线建筑物,达到了保护环境的目的,介绍施工步骤和要点,可供类似工程参考。     

北京地铁四号线区间工法的选择

文章简要论述了地铁区间施工方法的特点及适用条件,并结合北京地铁四号线的工程实践,分析了盾构法在地铁区间施工中的控制和影响因素.     

急曲线地铁隧道盾构法掘进技术研究

文章分析了急曲线地铁隧道盾构法施工易发生的问题,并结合宜山路-停车场区间长距离特急曲线隧道工程实例,介绍急曲线隧道的盾构法掘进技术.     

广州地铁大石-汉溪区间盾构工程施工关键技术

随着城市轨道交通事业的快速发展,盾构法施工技术在地铁隧道建设中已得到广泛应用.文章以广州市地铁三号线大石站(南)-汉溪站-市桥站(北)区间盾构工程为例,介绍了在复杂地质条件下利用盾构法修建地铁隧道的关键施工技术,对类似工程施工具有借鉴意义.     

地铁施工技术与施工管理分析

为进一步提升地铁施工质量,促进城市轨道交通可持续发展,对地铁施工中的明挖法与暗挖法（盾构法、浅埋暗挖法、矿山法）技术特点、适用范围等进行分析。同时,从科学控制施工成本与工期、加强施工现场风险管理、提升施工与管理人员专业能力、完善地铁施工现场管理制度以及加强施工现场监督管理等方面提出地铁施工管理策略,以期为地铁施工提供参考。     

市政施工企业进军地铁盾构施工高端领域的路径探讨

地铁建设工程,特别是地铁盾构施工本属于市政工程领域,但多年来传统市政施工企业进入该领域并持续发展的为数极少,央企等大型施工企业仍在该领域占有绝对的主导地位。文章系统地介绍和总结了深圳市市政工程总公司进入地铁盾构法施工高端领域的路径、历程、经验和思考,可供有计划进军地铁领域的行业企业参考。     

圆形盾构隧道衬砌管片的计算分析

盾构法以其安全、快速等优点在我国地铁隧道施工中得到了越来越广泛的应用,但其施工成本相对较高,其中管片造价占盾构隧道总施工费的30%以上.因此,合理地进行盾构隧道管片设计对于控制工程造价具有举足轻重的作用.文章结合工程实例,从荷载、土层参数等方面,采用当前地铁盾构隧道衬砌管片设计计算普遍采用的(修正)惯用法,对管片受力进行了分析研究,得出了一些有助于管片结构设计的结论.     

深圳地铁2号线土建2222标施工管理综述

地铁2222标由四站三区间组成,工程造价5.83亿元,工程内容涵盖了深基坑、大型明挖法车站、盾构法隧道、矿山法隧道,以及盾构空推过矿山法隧道等。工程特点为施工环境恶劣、地下管线密布、地质条件复杂多变、技术难度高、工期异常紧迫。施工过程中,项目部通过精心组织、科学决策、注重制度落实、讲求规范作业、狠抓节点工期、紧盯关键线路、实施工期考核与重奖重罚,使施工进度及质量安全得到了有效保障。地铁2222标的顺利完工,标志着市政总公司已经成功跻身地铁盾构施工高端领域,在深圳本土建筑业企业中率先实现从简单拥有盾构设备向基本掌握地铁盾构施工综合技术的历史性转变。     

浅议盾构法隧道施工过程中的安全控制措施

近年来盾构法隧道施工逐渐成为城市地下铁道施工的主流方法,其特有的施工安全管理问题也引起了广泛关注。文章结合深圳地铁二期工程2号线2222标侨香站—香蜜站—香梅北站两区间的施工实践,对土压平衡式盾构法隧道施工的安全生产进行了研究,并提出了对城市地铁及地下工程施工的安全控制措施。     

城市轨道交通盾构法隧道施工技术研究

为提高城市轨道交通隧道施工质量,需要积极完善技术方案、建构完整的技术管理模型,在夯实作业基础的同时,发挥盾构法施工技术的优势。基于此,对城市轨道交通盾构法隧道施工断面形式、技术要点进行研究,并结合工程案例,阐释盾构法隧道施工处理技术的具体应用,以期为城市轨道交通工程提供参考。     

波纹管切口机的研制

介绍了波纹管切口机的组成。通过对滚剪时作用力的分析,设计了滚剪机的主轴,并叙述了滚剪机的主要构造及使用方法,介绍了滚剪机进给结构的调整和刀具几何角度的确定。采用该设备后,提高了波纹管加工工效和加工质量,降低了生产成本,同时又改善了工作环境。     

Automatic ticketing on London underground

London Underground is currently going through a revolution in its fare collection systems. Magnetically encoded tickets are being introduced, obtainable from ticket office or self‐service machines, which are then checked automatically at start or finish of journey in the Underground's central zone. The microprocessor controlled equipment handles all accounting aspects of fare collection, because it is all part of a computer‐based network with centralized monitoring and control. The machinery was progressively installed from April 1987 to December 1988. This paper describes the history of the system, describes the new ticket and issuing machines, as well as discussing the development and project management tasks involved.     

国产长输管道焊接施工装备研究

近年来,长输油气管道焊接施工装备技术快速发展,大量新型管道施工装备投入管道工程现场应用,比如管道全位置自动焊机、管道管端坡口机、管道内环缝自动焊机已被分别用于管口焊接、坡口加工、管口组对。在大厚壁、高钢级、大口径管道施工中,这些设备既提高了管道施工效率,也提高了管口的焊接质量。根据实际应用情况,阐述了前述设备的结构、性能和其他技术特点,以使相关技术人员对国产管道施工装备有进一步的认识。     

Cost-effectiveness of reductions in greenhouse gas emissions from High-Speed Rail and urban transportation projects in California

A rising trend in state and federal transportation finance is to invest capital dollars into projects which reduce greenhouse gas (GHG) emissions. However, a key metric for comparing projects, the cost-effectiveness of GHG emissions reductions, is highly dependent on the cost-benefit methodology employed in the analysis. Our analysis comparing California High-Speed Rail and three urban transportation projects shows how four different accounting framings bring wide variations in cost per metric tonne of GHG emissions reduced. In our analysis, life-cycle GHG emissions are joined with full cost accounting to better understand the benefits of cap-and-trade investments. Considering only public subsidy for capital, none of the projects appear to be a cost-effective means to reduce GHG emissions (i.e., relative to the current price of GHG emissions in California’s cap-and-trade program at $12.21 per tonne). However, after adjusting for the change in private costs users incur when switching from the counterfactual mode (automobile or aircraft) to the mode enabled by the project, all investments appear to reduce GHG emissions at a net savings to the public. Policy and decision-makers who consider only the capital cost of new transportation projects can be expected to incorrectly assess alternatives and indirect benefits (i.e., how travelers adapt to the new mass transit alternative) should be included in decision-making processes.     

The estimation of transport cost functions: a methodological review

Abstract

The ex‐post facto cost of using private finance in roads is examined using a case study approach. The paper focuses on the first eight design, build, finance and operate (DBFO) roads commissioned by the UK Government’s Highways Agency and paid for through a system of shadow tolls. It carries out a financial analysis of the publicly available accounting information from the Highways Agency and its private sector partners for the first 6 years since the start of the 30‐year schemes in 1997. Publicly available financial information about the schemes was found to be limited and opaque. In 3 years, the Highways Agency had paid more than the construction cost. It was unclear whether the payments were higher than expected at financial close. Its private sector partners reported a post‐tax return on capital of 29% and an effective cost of capital of 11% in 2002, twice the cost of public finance. However, operating through a complex web of subcontracting creates additional, undisclosed sources of profit for their parent companies that make it difficult to establish the total cost of using private finance. The paper questions the wisdom of using private finance by providing evidence about the cost, including the cost of risk transfer.     

Mitigating environmental impacts in advance: Evidence of cost and time savings for transportation projects

The traditional model for mitigating a transportation project’s environmental impacts typically operates project-by-project and delivers the mitigation just-in-time. In contrast, the newer practice of advance mitigation comprehensively assesses and mitigates impacts from one or multiple transportation projects before or during project planning, sometimes long before project construction begins. The practice has gained adherents for its potential to improve ecological outcomes, by better aligning mitigation and conservation goals. Advance mitigation also stands to reduce mitigation costs, an important secondary benefit for transportation agencies with constrained resources. Evidence of cost savings, however, has been piecemeal and anecdotal. This paper advances knowledge of advance mitigation’s financial impacts in two ways. First, it critically assesses the evidence about cost savings realized through advance mitigation, both through avoided up-front costs and reduced project delay. Second, it directly estimates the project time savings that might accrue with advance mitigation of state highway projects in California. Overall, the balance of evidence is encouraging for transportation agencies that would introduce the practice, and general agreement exists on its financial benefits. Considering project delays related only to the environmental process, we estimate advance mitigation could reduce delivery times by 1.3–5.0 months per project. Still, we also identify factors limiting comprehensive analysis. Transportation agencies adopting advance mitigation practices into their operations could use a pilot approach that includes rigorous environmental and mitigation cost accounting; such pilots would build needed empirical evidence of advance mitigation’s financial and ecological outcomes.     

Evaluation of CO2 emissions from railway resurfacing maintenance activities

This paper is the world first to investigate the CO₂ impact of railway resurfacing in ballasted track bed maintenance. Railway resurfacing is an important routine maintenance activity that restores track geometry to ensure safety, reliability and utility of the asset. This study consisted of an extensive field data collection from resurfacing machineries (diesel-engine tamping machines, ballast regulators and ballast stabilisers) including travel distances, working distances, fuel consumption and construction methodologies. Fuel consumption was converted to a kg CO₂/m using the embodied energies of diesel. Analyses showed that tamping machines emitted the highest CO₂ emissions of the resurfacing machineries, followed by ballast regulators and ballast stabilisers respectively. Tamping machines processed 4.25 m of track per litre of diesel, ballast regulators processed 6.51 m of track per litre of diesel and ballast stabilisers processed 10.61 m of track per litre of diesel. The results were then compared to previous studies and a rigorous parametric study was carried out to consider long-term resurfacing CO₂ emissions on Australian railway track. The outcome of this study is unprecedented and it enables track engineers and construction managers to critically plan strategic rail maintenance and to develop environmental-friendly policies for track geometry and alignment restoration.     

Understanding suburban travel demand: Flexible modelling with revealed and stated choice data

We analyse the choice of mode in suburban corridors using nested logit specifications with revealed and stated preference data. The latter were obtained from a choice experiment between car and bus, which allowed for interactions among the main policy variables: travel cost, travel time and frequency. The experiment also included parking cost and comfort attributes. The attribute levels in the experiment were adapted to travellers’ experience using their revealed preference information. Different model specifications were tested accounting for the presence of income effect, systematic taste variation, and incorporating the effect of latent variables. We also derived willingness-to-pay measures, such as the subjective value of time, that vary among individuals as well as elasticity values. Finally, we analysed the demand response to various policy scenarios that favour public transport use by considering improvements in level-of-service, fare reductions and/or increases in parking costs. In general, demand was shown to be more sensitive to policies that penalise the private car than those improving public transport.     

Accounting for travel time variability in the optimal pricing of cars and buses

A number of studies have shown that in addition to travel time and cost as the common influences on mode, route and departure time choices, travel time variability plays an increasingly important role, especially in the presence of traffic congestion on roads and crowding on public transport. The dominant focus of modelling and implementation of optimal pricing that incorporates trip time variability has been in the context of road pricing for cars. The main objective of this paper is to introduce a non-trivial extension to the existing literature on optimal pricing in a multimodal setting, building in the role of travel time variability as a source of disutility for car and bus users. We estimate the effect of variability in travel time and bus headway on optimal prices (i.e., tolls for cars and fares for buses) and optimal bus capacity (i.e., frequencies and size) accounting for crowding on buses, under a social welfare maximisation framework. Travel time variability is included by adopting the well-known mean–variance model, using an empirical relationship between the mean and standard deviation of travel times. We illustrate our model with an application to a highly congested corridor with cars, buses and walking as travel alternatives in Sydney, Australia. There are three main findings that have immediate policy implications: (i) including travel time variability results in higher optimal car tolls and substantial increases in toll revenue, while optimal bus fares remain almost unchanged; (ii) when bus headways are variable, the inclusion of travel time variability as a source of disutility for users yields higher optimal bus frequencies; and (iii) including both travel time variability and crowding discomfort leads to higher optimal bus sizes.     

Condition monitoring of wooden railway sleepers

Wooden railway sleeper inspections in Sweden are currently performed manually by a human operator; such inspections are to large extent based on visual analysis. In this paper a machine vision based approach has been considered to emulate the visual abilities of the human operator to enable automation of the process. Digital images from either ends (left and right) of the sleepers have been acquired. A pattern recognition approach has been adopted to classify the condition of the sleeper into classes (good or bad) and thereby achieve automation. Appropriate image analysis techniques were applied and relevant features such as the number of cracks on a sleeper, average length and width of the crack and the condition of the metal plate were determined. Feature fusion has been proposed in order to integrate the features obtained from each end for the classification task which follows. The effect of using classifiers like multi-layer perceptron and support vector machines has been tested and compared. Results obtained from the experiments show that multi-layer perceptron and support vector machines have achieved encouraging results, with a classification accuracy of 90%; thereby exhibiting a competitive performance when compared to a human operator.