海底隧道注浆材料耐腐蚀性能研究及工程应用北大核心CSCD

海水具有较强的腐蚀性,极容易通过围岩薄弱区域侵蚀破坏隧道衬砌结构,为保证支护结构的耐久性,文章以普通硅酸盐水泥为基材,通过调节减水剂、速凝剂和高分子聚合物的掺量来设计耐腐蚀注浆材料的配合比,并对不同配合比注浆材料进行了耐腐蚀指标测试和现场注浆效果检验。室内试验结果表明,该注浆材料试块(水灰比为0.65~1.0)在海水浸泡360 d的强度腐蚀系数大于0.80,体积稳定性良好;为加快侵蚀速度,将试块浸泡在饱和MgSO;溶液中,注浆材料试块(水灰比为0.65)浸泡360 d的强度腐蚀系数大于0.80,体积稳定性仍良好。通过现场注浆试验对结石体强度进行测试,测试结果表明,在饱和MgSO4溶液中浸泡180 d的浆液结石体的点荷载强度均值为0.931 kN,比未浸泡试块的强度均值0.984 kN减少了5.5%,进一步验证了注浆材料的耐腐蚀性能。     

贵阳岩溶地层地铁盾构隧道工程中新型球状碳化钨刀具的研究与应用北大核心CSCD

在贵阳轨道交通3号线盾构隧道施工中,采用普通刀具易出现滚刀多边形磨损、偏磨、刀刃崩裂等异常磨损和刀圈脱落现象。为改进滚刀刀圈的耐磨、耐冲击性能,提高刀具的综合寿命,提出采用球状碳化钨刀具替换普通刀具,并介绍了激光熔覆焊工艺以及宏观磨损检测工艺。经过施工现场的实际应用,发现球状碳化钨刀具具有更好的耐磨性,新型球状碳化钨刀具平均磨损量为0.00255 mm/延米,相邻普通刀具平均磨损量为0.01655 mm/延米。在第338~736环掘进中,新型球状碳化钨刀具最大磨损量为0.015 mm/延米,刀具无崩刃现象,滚刀轴承、密封等均无异常,有效解决了普通刀具易磨损、磨损不均的问题,为喀斯特地质条件下盾构刀具的选型提供参考。     

隧道-洞口滑坡平行体系受力变形模式与计算方法研究北大核心CSCD

我国目前对隧道-滑坡工程的设计尚无可供参照的行业标准,尤其是滑坡洞口段隧道缺少相应的计算理论。文章首先以平行体系中隧道-洞口滑坡为研究对象,通过归纳总结滑坡地段隧道衬砌的病害特征,构建了相应的工程地质模型;然后将剩余滑坡推力视为导致隧道变形破坏的直接原因,通过荷载传递规律得到作用于隧道结构上的附加荷载,将其与围岩压力叠加推导出了隧道外荷载的计算公式;接着采用弹性地基梁理论,推导出滑坡推力作用下的隧道内力计算方法,从而得到隧道-洞口滑坡的受力变形模式及计算理论;最后通过模型试验对其合理性进行了验证分析,结果表明该方法与实际工程相符,能够为滑坡地段洞口隧道的设计提供参考。     

临近端头井盾构开挖引起土体沉降数值分析北大核心CSCD

文章以南昌地铁2号线雅苑路站施工为例,基于小应变硬化土体(HSS)本构模型,建立从端头井始发的双线盾构隧道掘进模型,分析了基坑开挖与双线盾构掘进共同作用下的土体沉降规律。结果表明:(1)加固盾构始发区土体可有效减弱区域范围内地表沉降,该区域内地表沉降量远小于区间隧道沉降量;(2)在同一埋深条件下,先建隧道地表沉降最大值高于后建隧道地表沉降最大值,地表横向沉降槽呈现非对称W型;(3)基坑开挖与盾构掘进共同作用下引起的地表沉降值,可以由二者单独作用产生的沉降值叠加计算得到。     

A framework for robustness analysis of road networks for short term variations in supply

There is a growing awareness that road networks, are becoming more and more vulnerable to unforeseen disturbances like incidents and that measures need to be taken in order to make road networks more robust. In order to do this the following questions need to be addressed: How is robustness defined? Against which disturbances should the network be made robust? Which factors determine the robustness of a road network? What is the relationship between robustness, travel times and travel time reliability? Which indicators can be used to quantify robustness? How can these indicators be computed? This paper addresses these questions by developing a consistent framework for robustness in which a definition, terms related to robustness, indicators and an evaluation method are included. By doing this, policy makers and transportation analyst are offered a framework to discuss issues that are related to road network robustness and vulnerability which goes beyond the disconnected definitions, indicators and evaluation methods used so far in literature. Furthermore, the evaluation method that is presented for evaluating the robustness of the road network against short term variations in supply (like incidents) contributes to the problem of designing robust road networks because it has a relatively short computation time and it takes spillback effects and alternative routes into account.     

Transport in Brasilia: the limits of aesthetics

The idea of moving the capital of the country from the coast to Brazil's vast but isolated interior goes back nearly two centuries. The basic motivation was to encourage construction of a national highway system, which in turn would encourage economic development of the interior and reduce regional disparities. The construction of Brasilia was an integral part of President Kubitschek's national development programme in the late 1950s, accompanied by expansion and sophistication of the energy, steel, automotive and road building industries. By 1975, highway transport times and costs had been reduced to some 20–26% of their former levels in most regions, with the Central‐West, where Brasilia is located, being the area with the greatest cost reductions. Despite the success of this development package, Brasilia's transport system has been less successful on a local and regional basis. Most of the problems within the city proper (the Pilot Plan), are due to the excessive emphasis on facilitating car traffic to the disadvantage of buses and non‐motorized traffic, while there are no local rail services. The regional transport problem stems from the location of the satellite cities far from the Pilot Plan, forcing low‐income bus riders to spend 3–4 hours daily in transit and up to 30% of the minimum wage on the journey to work. Improvements depend on institutional and policy changes affecting locational patterns, demand peaks and modal split.     

An inter‐Urban freight mode choice model

The Australian Railway Research and Development Organisation is conducting a study with one of its objectives being to determine factors affecting freight mode use. Part of this has included the development and calibration of freight mode choice models. This paper outlines the results obtained from the application of an Elimination‐by‐Aspects (EBA) model to this task. The paper describes the theoretical background to the EBA model, within the context of a general choice process, and then describes the results of the model when applied to three samples of shippers involved in regional freight transport.     

The challenge of railway policy in Europe

A conference organized in December 1993 by ESTI and CER discussed the major challenges facing the European railway industry. There are great opportunities in prospect for such an environmentally friendly industry, but there are many structural, financial and operational problems to overcome. The 1991 European Union Policy laid down the separation of the management of operation and infrastructure from the provision of railway transport services: measures for improving the financial structure of undertakings; and the introduction of international competition. The conference discussed the progress in restructuring, technical harmonization and interoperability and the practical issues involved in introducing competition.     

A planning model for multiple‐mode transportation system operations

The problem of generating a set of “good” transportation alternatives during the early and intermediate stages of transportation planning is addressed in this paper. A linear programming model of a multi‐modal transportation system is developed. The model is run interactively to determine optimal operating levels for all modes for various transport policy decisions. The model described is a component of a composite network generation model incorporating dynamic changes. The linear programming component determines optimal operating policies for given points in time. The composite model incorporates these in a dynamic programming framework to determine optimal staged investment policies over several time periods.