市政给中水管道设计优化分析

市政给排水管道结构设计是一项关乎管道安全的重要设计,设计人员往往根据以往经验和常规做法进行管道设计,忽略了管道安全计算,这将直接影响城市市政道路给排水管道工程的质量。结合实际项目,对给水、中水管道的常规管材球墨铸铁管进行结构计算分析,并根据计算结果选择相应的措施,进一步完善市政管道设计,在满足设计规划、规范和要求的基础上,提高设计质量,确保城市道路市政给排水管道正常、高效地运行。     

支撑式TBM与双护盾式TBM在设计选型中的比较

如何对硬岩隧道(洞)施工中使用的TBM进行设计选型?相信这是每个工程业主和设计院都需要面对的问题.通过对硬岩隧道(洞)掘进中,支撑式和双护盾式TBM的施工方法及设备功能包括对地质的适应性以及初期支护与混凝土衬砌型式、不良地质地段处理方法、出碴运输方式、环境影响等进行比较,并结合辽宁省大伙房输水一期工程输水隧洞施工中TBM的工程实践,提出了弥补支撑式TBM开挖和衬砌不能平行作业的改进构想,提出了采用栈桥式仰拱模板台车和全环内通式模板台车的施工方法.通过改进,可实现一模养生、一模浇注、第三模移动框架梁的作业工序.     

管棚超前支护在平顶直墙隧道中的优化设计

管棚法作为浅埋暗挖隧道的一种辅助工法在防止隧道塌方、控制地层位移方面发挥着重要作用.管棚设计需要确定两个基本参数--间距、截面尺寸.而管棚的设计理论还不够成熟.文章引入土拱原理可以计算管棚的最大间距;而对于截面尺寸.提出在弹性地基梁法的基础上,考虑隧道开挖影响并结合增量法进行计算较为合理.同时认为,两个基本参数的相互影响必须综合考虑,假定管棚直径进行间距设计,应根据管棚受力分析进行校核,通过多次循环假定、计算、校核以得到较为合理的管棚设计参数.     

复杂地层地铁旁通道冻结孔施工技术

在复杂地层中,对地铁旁通道采用水平冻结法施工是一种有效手段,而冻结孔施工又是旁通道工程的关键工序之一.结合上海地铁十一号线祁连山-真南路站区间旁通道施工实例,介绍了含承压水的砂性土复杂地层中旁通道冻结孔的施工技术,包括壁后预注浆加固、冻结孔开孔以及夯管等技术,对类似地质条件下旁通道冻结孔施工具有一定的参考价值和指导意义.     

城市干道下超浅埋平顶隧道全断面修建技术研究

位于厦门市的明发商业广场嘉禾路地下行车通道,所处围岩条件差、地下管线密集、工期紧张.该工程为平顶框架式通道,开挖跨度大、结构埋深浅、车流量大,为了保证施工的安全、地下管线的正常使用以及地面交通的正常运行,施工时必须严格控制结构变形、管线变形以及地表沉降.为此,通过有限元数值模拟,确定了全断面的施工方法,并综合应用了包括长管棚预注浆加固、尽快施做二次衬砌封闭成环和现场监控量测等在内的各项技术,使得工期缩短了1个月.通过该项工程全断面法修建技术的成功应用,获得了良好的社会、经济和环境效益,并总结出了该类工程施工时围岩变形及地表沉降的基本规律,这也为今后的相关工程积累了经验.     

Analyzing urban bus service reliability at the stop, route, and network levels

Improving the reliability of bus service has the potential to increase the attractiveness of public transit to current and prospective riders. An understanding of service reliability is necessary to develop strategies that help transit agencies provide better services. However, few studies have been conducted analyzing bus reliability in the metropolis of China. This paper presents an in-depth analysis of service reliability based on bus operational characteristics in Beijing. Three performance parameters, punctuality index based on routes (PIR), deviation index based on stops (DIS), and evenness index based on stops (EIS), are proposed for the evaluation of bus service reliability. Reliability involves routes, stops, punctuality, deviation, and evenness. The relationship among the three parameters is discussed using a numerical example. Subsequently, through a sampling survey of bus lines in Beijing, service reliability at the stop, route, and network levels are estimated. The effects of route length, headway, the distance from the stop to the origin terminal, and the use of exclusive bus lanes are also analyzed. The results indicate low service reliability for buses in Beijing and a high correlation between service reliability and route length, headway, distance from the stop to the origin terminal, and the provision of exclusive bus lanes.     

Vulnerability analysis for large-scale and congested road networks with demand uncertainty

To assess the vulnerability of congested road networks, the commonly used full network scan approach is to evaluate all possible scenarios of link closure using a form of traffic assignment. This approach can be computationally burdensome and may not be viable for identifying the most critical links in large-scale networks. In this study, an “impact area” vulnerability analysis approach is proposed to evaluate the consequences of a link closure within its impact area instead of the whole network. The proposed approach can significantly reduce the search space for determining the most critical links in large-scale networks. In addition, a new vulnerability index is introduced to examine properly the consequences of a link closure. The effects of demand uncertainty and heterogeneous travellers’ risk-taking behaviour are explicitly considered. Numerical results for two different road networks show that in practice the proposed approach is more efficient than traditional full scan approach for identifying the same set of critical links. Numerical results also demonstrate that both stochastic demand and travellers’ risk-taking behaviour have significant impacts on network vulnerability analysis, especially under high network congestion and large demand variations. Ignoring their impacts can underestimate the consequences of link closures and misidentify the most critical links.     

Superpave-13沥青混合料高温稳定性分析

文章结合天水过境高速公路路面实体工程,对不同孔隙率条件下的Super-pave-13高性能沥青混合料进行了车辙试验及SPT试验分析。结果表明,要保证Superpave-13沥青混合料具有较好的高温稳定性,其压实孔隙率应控制在4%～6.5%范围内。     

广西高速公路声屏障降噪效果研究

文章结合实地监测结果,对广西高速公路沿线现有各类声屏障的降噪效果进行了分析评估,并提出了相应的高速公路声屏障设计思路及建议。