沉管隧道预制管节顶推滑移系统摩擦试验研究

为了针对某大型沉管隧道预制管节的顶推滑移系统选择合适的摩擦面材料,文章对该顶推滑移系统的四组拟采用摩擦面材料(不锈钢板-PTFE、不锈钢板-NGE、普通钢板-PTFE、普通钢板-NGE)进行了静、动态摩擦系数测试。利用20 000 k N压剪试验机、采用双剪法进行了模拟测试试验。试验结果表明:(1)四组被测试摩擦面的摩擦系数中,不锈钢板与PTFE板的最小,普通钢板与PTFE板的最大;(2)锂基润滑油和水对减小不锈钢板与PTFE板之间的静、动摩擦系数效果都十分明显,但锂基润滑油对摩擦系数的减小效果会随着油层被挤压变薄而逐渐减弱。该试验结果为该顶推滑移系统的摩擦面材料选择以及摩擦面润滑处理措施提供了重要参考依据。     

大断面浅埋偏压隧道CRD法施工工序研究

文章以良村隧道CRD法施工为工程背景,布设了变形监测点及内力测试元件,分析了CRD法施工隧道围岩变形情况及结构内力特征,并对CRD法施工隧道在不同开挖顺序下的开挖过程进行了数值模拟,分析比较了不同开挖顺序时的围岩位移、应力变化情况。结果表明:CRD法对各分部施工工序影响较大,且各分部对拱顶下沉的影响程度从大至小依次为1部、2部、3部和4部;隧道内侧围岩压力大于外侧,钢支撑内力均为压应力,且拱腰位置轴力大于其它部位。比较隧道开挖变形的差异以及结构的受力特点,结合数值分析结果,得出了山体外侧先开挖方案无论在围岩变形还是隧道结构受力方面相比于山体外侧后开挖都较小,安全系数相对较高。因此,合理的施工工序应该是先进行山体外侧开挖并施作初期支护,然后再在山体内侧开挖施工。     

浅析内河航道节能现状及技术应用

内河航道在施工建设和运营管理期间会产生大量的能源消耗,抓好航道的节能减排对发展绿色交通具有重要作用。本文总结概况了目前我国内河航道节能减排现状及采用的关键技术,相关技术的推广将引导交通运输行业优化用能结构、促进产业协调发展。     

A stochastic model of traffic flow: Theoretical foundations

In a variety of applications of traffic flow, including traffic simulation, real-time estimation and prediction, one requires a probabilistic model of traffic flow. The usual approach to constructing such models involves the addition of random noise terms to deterministic equations, which could lead to negative traffic densities and mean dynamics that are inconsistent with the original deterministic dynamics. This paper offers a new stochastic model of traffic flow that addresses these issues. The source of randomness in the proposed model is the uncertainty inherent in driver gap choice, which is represented by random state dependent vehicle time headways. A wide range of time headway distributions is allowed. From the random time headways, counting processes are defined, which represent cumulative flows across cell boundaries in a discrete space and continuous time conservation framework. We show that our construction implicitly ensures non-negativity of traffic densities and that the fluid limit of the stochastic model is consistent with cell transmission model (CTM) based deterministic dynamics.     

Ridership drivers of bus rapid transit systems

We have collected information on 46 bus rapid transit (BRT) systems throughout the world to investigate the potential patronage drivers. From a large number of candidate explanatory variables (quantitative and qualitative), 11 sources of systematic variation are identified which have a statistically significant impact on daily passenger-trip numbers. These sources are fare, headway, the length of the BRT network, the number of corridors, average distance between stations; whether there is: an integrated network of routes and corridors, modal integration at BRT stations, pre-board fare collection and fare verification, quality control oversight from an independent agency, at-level boarding and alighting, as well as the location of BRT. The findings of this paper offer important insights into features of BRT systems that are positive contributors to growing patronage and hence should be taken into account in designing and planning BRT systems.     

穿越古滑坡川主寺隧道围岩破坏特征及稳定性研究

文章以川主寺隧道所处的工程地质条件为基础,通过现场调研分析了隧道围岩变形破坏形式主要为坍塌、掉块以及剥落.围岩稳定性三维有限元数值模拟结果显示,碎裂围岩自稳能力差,围岩变形以弹塑性变形、松弛变形为主;H型钢拱架支护结构对碎裂围岩稳定性起到积极的作用,并通过典型洞段现场位移监测数据分析结果得以证实.     

轴对称解对隧道衬砌水压力计算的适用性研究

文章根据渗流理论推导了隧道衬砌水压力的轴对称解,并利用数值分析方法研究了轴对称解对不同形状隧道断面与浅埋隧道的适用性.研究结果表明:轴对称解适用于非圆形隧道断面衬砌水压力的估算;隧道断面形状对衬砌水压力折减系数的影响较小,可以忽略不计,其影响大小主要由衬砌与围岩的渗透系数比值决定.对于浅埋低水头隧道,用轴对称解计算的毛洞流量Qm与数值解比较,其误差较大,最大误差为36.5％;但用来计算衬砌水压力p1以及衬砌后水流量Q1时,误差相对较小,最大误差为6.3％,特别是利用轴对称解得出的衬砌水压力值与利用数值解得出的衬砌水压力特征值最大误差仅为3.4％.     

基于Bayes判别分析方法的叙岭关隧道溶洞水源识别

基于Bayes判别方法,选取水化学常量组分作为判别指标,利用叙岭关隧道地区9个动态监测点的53个水样样本建立了该地区的水源判别模型.模型检验结果表明,其回判准确率为96.23％,具有较高的识别精度和工程推广能力.利用建立的判别模型,对叙岭关隧道1号溶洞内两个出水点RQ1和RQ2的水源进行了识别,并结合其流量动态变化特征、同位素分析结果,以及1号溶洞发育位置,推断1号溶洞内两个出水点的水源为P1m+q含水层中的岩溶地下水.根据判别结果,建议1号溶洞采取“以排为主”的原则加以处治,并尽量保留溶洞水的过水通道.     

Physical environments influencing bicyclists’ perception of comfort on separated and on-street bicycle facilities

This study investigates the impacts of physical environments on bicyclists’ perceptions of comfort on separated and on-street bicycle facilities. Based on a field investigation conducted in Nanjing, China, we find that physical environmental factors significantly influencing bicyclists’ perception of comfort on the two types of facility. Cyclists’ comfort is mainly influenced by the road geometry and surrounding conditions on physically separated paths while they pay attention to the effective riding space and traffic situations on on-street bicycle lanes.     

复合盾构刀具布置分析与研究

复合型盾构施工中,直接与岩土体接触的刀盘,其上刀具的布置是否合理直接影响盾构施工的顺利进行和施工成本。文章从复合盾构刀具布置的基本原则出发,指出了复合盾构滚刀刀间距的布置方式,利用等磨损原则分析了复合盾构刀具布置不同半径上每条轨迹应布置的刀具数量,阐述了不同刀具的螺旋曲线布置方法,并利用实例验证了利用该方法布置复合盾构刀具的合理性。