沥青路面冷再生沥青混合料配合比设计研究

冷再生沥青混合料施工技术是一种节能环保的公路路面修复技术,不但可以有效减少石料、沥青、水泥的需求量,降低工程成本,减少了资源浪费,并且与热再生技术相比可以有效降低CO2排放量。配合比设计是影响冷再生沥青混合料质量的关键因素,本文以某公路沥青路面修复工程为例,对沥青路面冷再生沥青混合料配合比进行研究,以加强冷再生沥青混合料质量控制。     

冷再生半刚性道路基层修筑技术

针对我国沥青路面结构的特点,依托实体工程开展就地冷再生半刚性基层配合比设计及施工工艺研究。     

乳化沥青冷再生混合料配合比设计及应用探讨

文章以某高速公路路面工程为例,对乳化沥青冷再生混合料级配、最佳含水率、水泥掺和量等进行配合比设计,并阐述其施工应用方法,为冷再生技术的应用提供参考。     

泡沫沥青冷再生混合料配合比试验研究

文章结合我国沥青路面施工技术规范的要求对泡沫沥青冷再生混合料进行配合比试验研究,以沥青膨胀率和半衰期为评价指标确定沥青最佳发泡条件和最佳拌和用水量,以间接抗拉强度(ITS)为控制指标确定最佳泡沫沥青用量,并通过对该泡沫沥青冷再生混合料的路用性能进行检测分析,验证了该配合比设计的合理性,为泡沫沥青冷再生混合料在实际工程中的推广运用和理论研究提供参考。     

乳化沥青冷再生混合料配比设计方法优化分析

依托山西省临汾市省道临夏线改造工程,针对乳化沥青冷再生技术,通过比较马歇尔设计法和Superpave体积法,分析了两者关键因素的差异性,结合2种设计方法优化了冷再生沥青混合料的设计方案,提出了击实体积校验综合设计法及评价方法。通过实例将混合料的关键指标与规范设计值进行对比,评价了优化设计方案。研究结果表明优化后的设计及评价方法具有一定的可行性,可用于乳化沥青冷再生混合料的目标配合比设计。     

泡沫沥青冷再生基层研究进展

为缓解地球资源紧缺、环境污染等问题,使冷再生技术更好地应用于道路工程中,本文综合整理了泡沫沥青、泡沫沥青冷再生混合料(CRMFA)的制备机理、性能影响因素与工程应用,从多方面介绍了目前泡沫沥青冷再生技术的研究进展。研究认为,目前CRMFA应用方面的研究仍有不足,后续研究应更好地同时兼顾配合比设计与工程实践,并建立基于不同环境、不同工况的CRMFA性能预测模型。     

水泥就地冷再生技术在福州三环路的应用

文章结合福州市三环路试验路水泥就地冷再生技术应用实例,介绍了水泥就地冷再生混合料配合比设计方案及施工工艺,并通过工程现场评定与验收,验证了水泥就地冷再生技术的应用效果。     

沥青路面就地冷再生工艺探讨

本文通过工程实例,针对旧沥青路面的就地冷再生改造工程,从混合料配合比设计、旧路病害处治、添加集料及水泥的摊铺整平、冷再生机工作、压实、养护等各个工序的质量控制方面进行了探讨,为同类工程提供参考。     

废旧沥青路面材料大比例再生利用技术

近年来,随着环保意识的增强,对废旧路面材料的大比例、有效利用成为研究关注的热点。针对热再生生产及施工中的技术难点,项目研究单位以大比例热再生沥青混凝土材料设计、热再生混凝土长期性能、生产及施工工艺为突破口进行研究。该项技术已先后在北京的二环路大修工程、韩西路大修工程、南六环大修工程等工程中得到应用,应用里程大于35 km。针对乳化沥青厂拌冷再生技术应用中的难点,项目研究单位以乳化沥青自主生产、乳化沥青冷再生混合料配合比设计及性能研究、含有乳化沥青冷再生层的新建道路及大中修道路结构优化、乳化沥青冷再生混合料施工技术等问题为突破口进行深入研究。该项技术已先后在北京地区进行了十余项工程应用,共铺筑乳化沥青冷再生混合料5.3万吨,消耗旧料近5万吨,应用里程大于32 km。     

旧沥青路面乳化沥青厂拌冷再生关键技术研究

结合具体工程对旧沥青路面铣刨料的乳化沥青厂拌冷再生技术进行了系统研究。首先对铣刨料的级配进行分析评价。其次,确定了掺加水泥的乳化沥青冷再生混合料配合比,并进行了室内性能评价。同时对冷再生沥青混合料的生产工艺以及施工质量控制等环节进行了系统介绍。     

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 new approach for modeling of Fundamental Diagrams

According to the intra-vehicle interaction, a traffic flow can generally be divided into three homogeneous states (1) that of free driving, (2) that of bunched driving, and (3) that of standing. The parameter describing the state of free driving is the desired speed, for the state of bunching it is the intra-vehicle gaps (time headway) within the convoy and the mean speed of the convoy, and for the state of standing it is the maximum jam density. These are the most essential parameters which do not depend on the actual traffic situation.This paper introduces a new model which considers the Fundamental Diagram (equilibrium speed–flow–density relationship) as a function of the homogeneous states. All traffic situations in reality can be considered as combinations of the homogeneous states and therefore can be described by the essential parameters mentioned above. The non-congested (fluid) traffic is a combination (superposition) of the states of free driving and bunched driving, the congested (jam, stop, and go) traffic is a combination of the states of bunched driving (go) and standing (stop). The contribution of the traffic states within the differently congested traffic situations can then be easily obtained from the queuing and probability theory. As a result, Fundamental Diagram in all equilibrium traffic situations is derived as simple functions of the essential parameters.According to the new model the capacity of freeways and rural highways can be determined by measuring the essential parameters. This is much easier than measuring the capacity directly.Furthermore, the probabilities of the various traffic states can be obtained from the new model. This leads to new possibilities in real-time controlling and telematics.The new model is verified by comprehensive measurements carried out on freeways and rural highways in Germany.     

输油站场清管系统应力分析

清管是输油管道重要的常规作业之一,是保证管线长期按照设计输量运行的重要保障。目前,对输油站场的清管系统在运行工况下的应力分析较少,特别是没有考虑由于清管器本身对管道所造成的冲击对管道应力分布的影响,所以有必要对输油站场清管工况下的管道进行应力分析。文中采用CAESAR Ⅱ软件对某输油站清管工况下管道系统进行应力分析,建立了清管器受力模型,通过编制VB程序计算了清管器的冲击产生的集中应力大小,并以假设清管器产生的冲击力最大的情况下得出整个管道的一、二次应力分布,找出了一、二次应力分布的关键点,并进行了校核,满足管道的强度要求,所用方法有利于更好地保证清管作业安全。     

Competition policy and the liberalisation of European aviation

The European aviation industry is undergoing a process of liberalisation. One of the important lessons of American deregulation was that the industry is not perfectly contestable. One implication of this is that actual competition on a route is important in order to be able to secure the benefits of deregulation or liberalisation. Another is that effective competition policy is important in order to prevent anti-competitive mergers or predatory behaviour. This paper reviews the merger investigations in European aviation which have accompanied the search by carriers to secure the benefits of market power, and considers the extent of route competition within the European Community and its relationship to the different route licensing policies of different national governments. The paper considers the extent of present competition on the busiest routes, and stresses the importance of cabotage rights in opening up the European market to effective competition.     

The quality of survey data: Telephone versus face-to-face interviews

Those designing surveys and producing data have always been concerned about its quality. The increasing stringency of the financial constraints which affect public authorities and the increased scope of involvement in the regulation of urban travel has led us to pay even greater attention to the quality of data. This issue is frequently covered in the literature on survey methods. However, comparisons between different survey methods are more rarely conducted. The decision to conduct such an analysis is partly the result of the development of telephone use to the detriment of other survey modes in many countries and also the development of Computer-Aided Telephone Interviewing (CATI) which facilitates the running and monitoring of the survey.This paper examines several aspects of this question in order to compare the performance of telephone and face-to-face interviews. The first aspect is the representativeness of the sample, and therefore relates mainly to the issue of nonresponses and the choice of a sample base. The second concerns the accuracy of the information and involves the choice of a survey area and the recording of all trips, including short-distance travel. Finally, the quality of data is obviously determined by the quality of the responses given by those interviewed.The answers we give frequently depend on the objective of the surveys, which leads us to put forward a table which summarizes the performance of telephone and face-to-face interviews on the basis of the main objective of the survey. Broadly, the telephone seems to be the favoured tool for surveys in the area of transport planning and surveys which aim to provide data for forecasting models, mostly on the grounds of cost. However, face-to-face techniques are often preferred for surveys which aim to discover and analyze the factors which explain individual travel behaviour.     

Development and evaluation of a knowledge-based system for traffic congestion management and control

This paper describes a real-time knowledge-based system (KBS) for decision support to Traffic Operation Center personnel in the selection of integrated traffic control plans after the occurrence of non-recurring congestion, on freeway and arterial networks. The uniqueness of the system, called TCM, lies in its ability to cooperate with the operator, by handling different sources of input data and inferred knowledge, and providing an explanation of its reasoning process. A data fusion algorithm for the analysis of congestion allows to represent and interpret different types of data, with various levels of reliability and uncertainty, to provide a clear assessment of traffic conditions. An efficient algorithm for the selection of control plans determines alternative traffic control responses. These are proposed to an operator, along with an explanation of the reasoning process that led to their development and an estimation of their expected effect on traffic. The validation of the system, which is one of only few examples of validation of a KBS in transportation, demonstrates the validity of the approach. The evaluation results, in a simulated environment demonstrate the ability of TCM to reduce congestion, through the formulation of traffic diversion and control schemes.     

Effects of built environment on walking at the neighbourhood scale. A new role for street networks by modelling their configurational accessibility?

The hypothesis of this paper is that some features of the built environment, particularly those concerned with the accessibility of the street network, could be associated with the proportion of pedestrians on all trips (modal split) found in different parts of a city. Quantitative analysis (bi-variate correlation and a multiple regression model) was used to establish the association between variables. The study area covered a substantial part of the metropolitan area in Madrid, Spain. Results showed a consistent influence of five particular indexes in the multi-variate model. Not surprisingly for this kind of research, four of them described density and mix of land uses. But perhaps more interestingly, the first one was a measure of the accessibility of the public space network, a less prominent variable in literature to date. This variable is called herein configurational accessibility, calculated using Space Syntax, an urban morphology theory. The relevance of configurational accessibility is probably related to its surprising ability to synthesize global and perceived properties of street networks at the same time. The findings introduce the idea that the configuration of the urban grid can influence the proportion of pedestrians (as a part of total trips in any transport mode) who choose to walk on single-journey trips. The discussion links with the current debate about walkability indexes and the need of empirical support for the chosen variables and also with transport planning. Because the relevance of the street network’s role is not so easy to grasp, inputs from configurational theory and the pedestrian potential underlying this fact are also discussed at the end of the paper.     

Financing urban rail projects: The case of Los Angeles

This paper describes the potential use of the financing strategy of value capture or benefit assessment for an urban mass transportation project. The paper describes the legal background to the use of benefit assessment, and the process of implementation for the first construction phase of the Los Angeles Metro Rail project. The process of developing the benefit assessment structure was a consultative one, utilizing technical inputs from a team of specialist consultants, a task force consisting of major developers and property owners in the affected area, and politicians representing many of the interests in the region. The initial benefit assessment districts were set up to raise $130 million of the cost of the first 4.4 miles of the rail project, and are based on the benefits accruing to certain categories of property in the vicinity of stations. The assessment would be collected for about 18 years and bonding would be used to provide the capital at the time of construction.The paper describes the procedure for setting boundaries, the structuring of the assessment rates, the definition of benefiting properties, and the uses and tenure of the assessment. In almost all cases, the theory of value capture indicated a different result than was achieved from a consensus of the task force, and the nature of these differences is explored in the paper. The establishment of the benefit assessment districts withstood early court challenges, but has subsequently been appealed and was overturned on appeal. Action is pending with the Supreme Court currently, and efforts are also underway to pass new legislation to deal with some of the issues raised in the court proceedings.