现代注浆技术的开拓应用及发展

文章介绍了目前已经出现的几种注浆法开拓应用的新技术,如锚注支护、爆破注浆、立井"三同时"施工工艺、电化学注浆等;提出了"抽注式"注浆、磁化水注浆、注浆拔孔桩等一些新的注浆技术开发思路;并指出今后应加强制定注浆技术规范、试验标准、预算定额、研制注浆试验仪器、加大注浆理论与技术研究力度.     

岩溶富水隧道可控注浆施工技术研究

以重庆市轨道交通一号线中梁山隧道工程岩溶富水段注浆堵水工程为例,综合分析了帷幕注浆的理论数据和中梁山隧道岩溶富水段超前帷幕注浆堵水实践经验数据,以探索超前帷幕注浆可控施工技术;在实践中,通过注浆终孔可控、注浆终压可控、注浆量可控、注浆材料可控等方法来实现帷幕注浆可控,以达到快速、安全、文明、高效的注浆施工。     

多孔介质注浆模拟试验研究进展

基于注浆工程的隐蔽性和复杂性特点,注浆模拟试验成为研究注浆过程和注浆理论的重要途径.文章对多孔介质注浆理论计算方法进行了阐述和总结,介绍了多孔介质注浆模拟试验中对扩散性能和结石体强度、注浆压力和被注介质内部压力以及渗透系数和渗透稳定性等注浆参数规律研究的现状和进展,并对多孔介质注浆模拟试验的研究方向进行了展望.     

注浆处治盾构下穿建筑物渗水沉降的效果分析

天津地铁3号线盾构下穿某既有建筑物时因地下水渗漏引起建筑物沉降,文章以注浆抬升处治工程为研究对象,结合监测数据,采用数值模拟方法分析了在隧道渗水条件下注浆抬升既有建筑物的效果,在此基础上分析了注浆点位置、注浆时间对注浆抬升效果以及对隧道的影响。研究结果表明:浅孔注浆时补偿注浆率较高,所需注浆量明显低于深孔注浆,但补偿注浆率波动程度较大,建筑物倾斜显著增加;深孔注浆时注浆压力导致隧道弯矩急剧增大,为浅孔注浆时的3.7倍,隧道弯矩影响范围均约为注浆区宽度的1.5倍;适当增加单次注浆时间,建筑物倾斜增量较小,且建筑物测点抬升量显著增加,补偿注浆率明显增大,注浆抬升效果更好。     

圆梁山隧道粉细砂充填型溶洞注浆技术探讨

文章以圆梁山隧道2号粉细砂充填型溶洞注浆施工为例,介绍了在高压、富水、粉细砂充填型溶洞注浆施工中其注浆材料、注浆参数以及注浆工艺选择等方面应注意的问题,可为今后类似工程的注浆施工提供借鉴.     

土建工程施工中注浆技术的发展

从注浆技术的定义和分类、注浆材料、注浆方法、注浆效果的监控与检测等几个方面进行综述,介绍了土建工程施工中注浆技术的特点及发展趋势。     

大直径盾构掘进非对称同步注浆地层扰动规律研究

为了研究大直径盾构施工过程中非对称同步注浆对土体扰动的影响规律，基于钱江隧道南岸始发段超大直径泥水平衡盾构施工，通过有限元方法重点模拟了盾尾同步注浆过程，并与现场监测数据进行对比分析。在既有解析解的基础上通过二次开发实现有限元模型同步注浆压力的非均匀分布模式，使其充分反映非对称注浆工况。模拟中考虑了非对称注浆压力比、注浆率和注浆缺陷分布模式（即局部注浆压力不足位置）等因素对周边地层扰动的影响。研究表明，不对称注浆压力导致沉降槽呈不规则状，注浆压力较大的一侧易发生地表隆起；不对称注浆压力比与地层损失率呈线性负相关；随着注浆率增加，深层土体沉降值不断增加，当深度增加时，这种趋势会更加明显；不同注浆缺陷分布模式对地表沉降有不同程度的影响，顶部注浆孔压力对地表沉降量的影响较大，而腰部注浆孔压力对地表沉降槽宽度系数影响较大，底部注浆孔压力对地表沉降的影响相对较小。     

地铁隧道压底注浆研究

在地铁隧道现场注浆试验的基础上,研究了压底注浆机理,讨论了压底注浆设计、施工要点,比较了注浆后隧道隆起的计算方法;利用现场实测隧道变形资料,通过反馈分析确定了注浆等效压力的经验公式,对地铁隧道下方压底注浆设计与施工有一定的指导意义。     

百罗高速公路路基注浆加固工程实例分析

文章介绍了路基注浆的原理和流程,分析了传统路基注浆施工中存在的问题,从计量方式和注浆方法两个方面提出了路基注浆施工的改进方法,并结合百罗高速公路工程实例,评述了路基注浆改进方法的应用效果。     

钻爆法海底隧道软弱破碎地层注浆加固堵水技术浅析

为了解决海底隧道穿越软弱破碎地层所遇到的技术难题,文章针对海底隧道软弱破碎地层特点,从超前地质预报、注浆方案选择标准、注浆材料、注浆参数、注浆工艺以及注浆效果检验方面进行了分析总结,提出了钻爆法海底隧道软弱破碎地层注浆加固堵水技术和总体对策,并阐述了其在工程中的应用效果.     

Technical and environmental effects of biodiesel use in local public transport

Biodiesel use in local public transport could be especially significant in improving air quality in cities. The purpose of the experiments described in this paper was to evaluate the various (10, 20 and 50%) blends of biodiesel with diesel in the context of the engine and pollution aspects. As regards the experimental use of these findings on municipal buses, these experiments were the first reference in Hungary. The ages (15–20 years) and types of buses (Ikarus-280, Ikarus-260) used in the experiments are still common vehicles in Hungarian public transport. During our measurements, there was a significant difference between the change in fuel consumption of articulated and solo buses in traffic when compared to test bench measurements. The proportion of the engine performance reduction is nearly the same as that for biodiesel share in the blends. Most pollutants were decreasing (both at idle and full rpm), but this reduction is not directly proportional to the increase of the blending percentage. However, as for CO₂, emission increase was observed in the case of idle rpm in comparison to normal diesel operation, even though this phenomenon was not due to biodiesel use, but the catalytic converter and the fact that biodiesel was used for the first time in the engine concerned.     

含蜡热油管道清管过程的卡堵风险分析

现场清管作业时,清管器经常被卡堵,严重时会影响生产.因此,为降低热油管道清管过程中的卡堵风险,根据清管器在含蜡热油管道中的受力情况和运行规律,结合输油管道的现场运行管理经验,分析含蜡热油管道清管过程可能遇到的卡堵,对此提出可靠的应对措施,以杜绝含蜡热油管道周期性清管中各种事故的发生,保证热油管道清管工作的安全进行,为今...     

频繁爆破下隧道内振动传播的数值研究

为揭示频繁爆破下隧道内振动传播衰减规律,文章以蒙华铁路段家坪隧道为工程背景,利用LS-DY NA建立了三维隧道模型,模拟分析了多次爆破下隧道内近区和中远区的振动传播规律。结果表明,质点垂向峰值振速随距离和爆破次数的增大而减小,少数振速有增大的现象;近区振动衰减较快,中远区振动衰减比近区缓慢;中远区a值比近区至少小12.5%,但整体上二者的a值随爆破作用次数的增加呈缓慢上升趋势;系数K随爆破作用次数的增加而降低,近区K值降低速率普遍大于中远区,且近区K值比中远区至少大29.1%;频繁爆破下,中远区比近区较符合萨道夫斯基经验公式。     

An analysis of rail freight operational efficiency and mode share in the British port-hinterland container market

The growth in container shipping poses considerable challenges to efforts to reduce the negative externalities associated with freight transport. There are particular concerns about the impacts of the associated port-hinterland freight flows. Through empirical research, this paper examines trends in the operational efficiency of the British port-hinterland container rail freight market and to assess the impacts of any changes on the overall sustainability of this market. Original survey work conducted in 2007 and 2015 has allowed longitudinal and cross-sectional analysis of the characteristics of this market.The survey findings reveal that rail’s mode share of port container throughput (in TEU) has increased from 14.7% in 2007 to 16.6% in 2015 and it is likely that its share of the associated hinterland activity has also risen. Rail was carrying 25% more TEU by 2015 without an increase in train service provision. Increases in mean train capacity and mean load factor were observed, leading to growth in the mean train load from 44 TEU in 2007 to 55 TEU in 2015. This considerable improvement in operational efficiency is expected to have reduced the negative externalities per unit of transport activity associated with the rail-borne hinterland container flows, though scope is identified for further improvements in sustainability.     

Urban walkability considering pedestrians’ perceptions of the built environment: a 10-year review and a case study in a medium-sized city in Latin America

ABSTRACT

Numerous methodologies measuring walkability have been developed over the last years. This paper reviews the Walkability Index (WI) literature of the last decade (2009–2018) and highlights some limitations in the current approaches. Only a few studies have evaluated walkability in Latin America, mainly in big cities but not in medium and small-sized cities in the region, which present their own urbanisation dynamics, security issues, sidewalk invasion problems, and poor planning. Furthermore, most WIs in the literature use objective mesoscale variables to assess walkability in a given area. This paper contributes to filling these gaps by generating new evidence from a medium-sized city in Latin America to question if characteristics of the built environment encourage walking trips, as found in the literature, are transferable among regions. The study also proposes a novel index comprised of microscale and mesoscale built environment variables to assess walkability using virtual tools and considering users’ perceptions. The WI estimation relies on ranking probability models. The results of the case study suggest that subjective Security and Traffic Safety are the most crucial factors influencing walkability in these kind of cities, which is different from what is found in the literature from cities in developed countries where Sidewalk Condition and Attractiveness are the most important factors. Security appeared to be strongly associated with a subjective dimension, represented by the fear of crime or perceived risk for crime, instead of the actual occurrence of crimes. This result evidences the importance of the physical attributes of the real world and how they are captured, judged, and processed by pedestrians. Then, regional transferability of WIs needs to be done carefully. Finally, results in this paper highlight the importance of microscale built environment characteristics in the WI formulation in these cities. Results are in line with other research in some cities of the region, which found that microscale variables such as pavement quality and presence of obstacles on the sidewalks are relevant components to promote walkability.     

The role of attitude structures,direct experience and reframing for the success of congestion pricing

Congestion pricing was introduced in Stockholm in 2006, first as a trial followed by a referendum, and permanently from 2007. Public attitudes to the charges became more negative during the period from the decision to the start of the system. Once the trial started, public attitudes became dramatically more positive over the following years, going from 2/3 against the charges to more than 2/3 in favor of the charges. Self-reported changes in behavior and attitudes considerably underestimate actual changes: about 3/4 of the decrease in car trips and more than half of the change in attitudes seem to have gone unnoticed by respondents, ex post. Self-interest and belief in the charges’ effectiveness strongly affect attitudes at any given point in time, but can only explain a minor part of the change in attitudes. I suggest that the debate and the shift in attitudes can be understood as a public and political reframing of the congestion charges over time.     

Risk of increasing temperature due to climate change on high-speed rail network in Spain

With more than 3,200 km of track, the Spanish high-speed rail network is the longest network in Europe and the second largest in the world after China. Due to its geographical location in southern Europe, the entire network is exposed to periods of elevated temperatures that can cause disturbances and severe disruptions such as rail deformation, or in the worst case, lateral track buckling. In this study, the vulnerability of the current Spanish high-speed rail network is analysed in terms of track buckling failures with a Monte Carlo simulation. Downscaled temperature projections from a range of Global Climate Models (GCMs), under three Representative Concentration Pathways (RCP4.5, RCP6.0 and RCP8.5), were forced in a buckling model and particularized for different segments of the network. With that, the proposed methodology provides the number of rail buckles expected per year by assuming current maintenance standards and procedures. The result reveals significant increase in the occurrence of buckling events for future years, mainly in the central and southern areas of mainland Spain. However, relevant variations are found in different climates and time horizon scenarios in Spain. The anticipated buckling occurrences highlight the vulnerability of the Spanish rail network in the context of global warming scenarios. Overall, the proposed methodology is designed to be applicable in large-scale railway networks to identify potential buckling sites for the purpose of understanding and predicting their behaviour.     

Energy use in passenger transport in OECD countries: Changes since 1970

This paper analyzes some of the changes that took place in the structure of energy use for passenger travel in industrialized countries. Data is presented on energy use and travel activity for the four major modes of travel — automobile, bus, rail and air — for eight OECD countries: the United States, Japan, the United Kingdom, West Germany, France, Italy, Sweden, and Norway. We use the Laspeyres and Divisia indices to analyze the causes of the change in energy use between 1970 and 1987. The total change in energy use for travel is explained by changes in domestic passenger transport volumes, the mix of modes of travel, and the energy intensities of each mode. We have found two important effects that have a fundamental impact on energy use for travel since 1970. First, shifts among modes of transport towards more energy-intensive ones and large increases in volumes of travel (measured in passenger-kilometers) increased energy use for travel in many OECD countries, often more rapidly than the overall growth in GDP. Second, energy intensities, measured in mJ/passenger-kilometer, of passenger transport fell only in a few countries between 1970 and 1987. Even though individual automobiles have become more energy-efficient, greater size, power, and weight, worsening traffic conditions in Japan and Europe, and fewer people in cars restrained or even offset efficiency improvements. Particularly notable are the increases in intensities in Japan and Germany. The most important exception to this trend was the United States, but the intensities of land-based travel remain higher there than in most other countries. These findings lead to a pessimistic outlook for future energy use for travel. After all, if little or no energy was saved during the decades of high fuel prices, what can be expected in the 1990s?     

Distributed work and travel behaviour: The dynamics of interactive agency choices between employers and employees

This paper develops a framework within which multiple agents make discrete choices in respect of a common objective – the determination of participation in distributed work, especially the opportunities and constraints associated with telecommuting. Ideas in discrete choice theory and game theory are combined to define a set of choice experiments in which employees and employers interact in arriving at a choice path in a distributed work context. A state choice experiment with offers and feedback, known as an interactive agency choice experiment (IACE), is empirically investigated in the context of telecommuting options with an exploratory sample of employees and employers in Sydney, Australia. The approach highlights the role of information and negotiation in breaking down the barriers to more flexible work activity, to deliver potential benefits to the transport system such as reduced traffic congestion and environmental sustainability. The paper identifies the types of incentives that an employee/er has to offer the employer/employee in securing effective telecommuting. This revised version was published online in June 2006 with corrections to the Cover Date.