隧道开挖中的应力旋转和裂隙塑性变形问题研究

通过对隧道开挖过程进行三维数值模拟,分析了隧道开挖过程中主应力方向的旋转变化,研究了主应力旋转与隧道裂隙塑性变形的关系,验证了"考虑应力主轴旋转的广义塑性原理"的正确性,并将数值模拟结果和相关试验成果进行了对比,得出了一致性的结论。研究结果表明,应力旋转基本在隧道开挖前后10 m左右的距离内完成,隧道开挖过程中的应力旋转可以引起裂隙塑性变形的突变,且对竖向和斜向裂隙的影响较大;可以根据应力旋转的变化规律合理地选择支护时机,依据应力旋转对裂隙的影响对隧道的重点部位进行超前加固。     

Hysteresis phenomena of a Macroscopic Fundamental Diagram in freeway networks

Observations of traffic pairs of flow vs. density or occupancy for individual locations in freeways or arterials are usually scattered about an underlying curve. Recent observations from empirical data in arterial networks showed that in some cases by aggregating the highly scattered plots of flow vs. density from individual loop detectors, the scatter almost disappears and well-defined macroscopic relations exist between space-mean network flow and network density. Despite these findings for the existence of well-defined relations with low scatter, these curves should not be universal. In this paper we investigate if well-defined macroscopic relations exist for freeway network systems, by analyzing real data from Minnesota’s freeways. We show that freeway network systems not only have curves with high scatter, but they also exhibit hysteresis phenomena, where higher network flows are observed for the same average network density in the onset and lower in the offset of congestion. The mechanisms of traffic hysteresis phenomena at the network level are analyzed in this paper and they have dissimilarities to the causes of the hysteresis phenomena at the micro/meso level. The explanation of the phenomenon is dual. The first reason is that there are different spatial and temporal distributions of congestion for the same level of average density. Another reason is the synchronized occurrence of transitions from individual detectors during the offset of the peak period, with points remain beneath the equilibrium curve. Both the hysteresis phenomenon and its causes are consistently observed for different spatial aggregations of the network.     

Real time queue length estimation for signalized intersections using travel times from mobile sensors

We study how to estimate real time queue lengths at signalized intersections using intersection travel times collected from mobile traffic sensors. The estimation is based on the observation that critical pattern changes of intersection travel times or delays, such as the discontinuities (i.e., sudden and dramatic increases in travel times) and non-smoothness (i.e., changes of slopes of travel times), indicate signal timing or queue length changes. By detecting these critical points in intersection travel times or delays, the real time queue length can be re-constructed. We first introduce the concept of Queue Rear No-delay Arrival Time which is related to the non-smoothness of queuing delay patterns and queue length changes. We then show how measured intersection travel times from mobile sensors can be processed to generate sample vehicle queuing delays. Under the uniform arrival assumption, the queuing delays reduce linearly within a cycle. The delay pattern can be estimated by a linear fitting method using sample queuing delays. Queue Rear No-delay Arrival Time can then be obtained from the delay pattern, and be used to estimate the maximum and minimum queue lengths of a cycle, based on which the real-time queue length curve can also be constructed. The model and algorithm are tested in a field experiment and in simulation.     

输水盾构隧洞复合衬砌结构设计计算研究

软土有压输水盾构隧洞采用管片外衬和整筑预应力内衬作复合式衬砌的设计计算中,为能较好考虑内衬与外衬管片的相互作用,以及内衬预应力荷载在隧洞施工和运营各阶段对复合衬砌结构受力的影响,本文提出了一种新的实体叠合计算模型。由于确定管片纵缝接头抗弯刚度的复杂性,文中建议对用数值模拟管片纵缝接头刚度采用了一种非线性耦合弹簧＂接触对＂的模拟系统。在采用实体单元建模的条件下,由于计入管片接头刚度的力学处理困难,文中研究了一种能以模拟管片接头刚度的简化计算方法。根据内、外衬砌接触界面处理方式的不同,文中提出了5种适合不同界面条件内、外层衬砌的相互作用模型。此外,本文还研制了内衬预应力荷载的一种转化程序,以解决采用等效荷载法施加预应力时的前处理问题。上述各点创意构思已在南水北调中线一期穿黄隧洞的结构设计研究中得到了具体反映和成功应用。     

钱江通道及接线工程钱江隧道设计综述

在建的钱江隧道是高速公路项目钱江通道及接线工程下穿钱塘江的控制性工程,隧址位于钱塘江人海口,工程地质条件及河段水文条件复杂.隧道过江段采用盾构法施工,隧道直径为15.0 m,是目前世界上最大的盾构法隧道.文章详细介绍了钱江隧道工程的建设环境、建设标准,以及隧道平面、纵断面及横断面布置等总体设计方案,并对超大直径盾构隧道结构及防水、盾构浅埋下穿河流、软土地层深基坑、盾构段立体化平行作业及综合防灾系统等关键技术进行了阐述.     

基于ANP方法的公交车实时调度策略选择研究

给出了公交车的4种实时调度策略,包括滞站调度、跳站调度、短掉头和发车调度.4种调度策略各有优缺点,但是在特殊环境之下,如何考虑选择不同的调度策略是管理者面临的重要问题.文中建立了ANP方法,选择12个指标对4种不同的调度策略进行对比,考虑指标与因素之间的反馈与关联,更接近于决策的实际情况,有助于提供更好的方案选择.     

正态分布在公交营运管理中的应用

本文提出一种用于LPS数字智能公交系统的营运调度算法.通过正态分布曲线及面积分布图认识影响营运调度质量的原因,通过对营运调度数据的动态跟踪、修正,达到智能调度的目的.     

城市客运模式选择研究

国内目前各城市的客运发展存在着地域之间不平衡,发展面临问题众多的局面,行业管理存在较多待破解的关键性问题.本文从城市客运管理运营模式作为研究视角,通过审视和比较世界不同城市交通的发展模式,结合影响城市客运模式的主要决定因素,论证国内目前的发展阶段和城市客运模式,研究提出适合于中国特点的、可持续发展的城市交通发展模式.     

应用Excite Designer对汽油机进行曲轴轴系分析

为解决曲轴轴瓦间隙不合理而造成的轴瓦易磨损问题,本文运用AVL—Excite Desirer对直列四缸汽油机机曲轴轴系进行了模拟分析,得到曲轴主轴承设计间隙下限情况下（目前设计间隙0．024-0．048）的各主轴承相关参数。同时就主轴承间隙对最小油膜厚度和最大油膜压力的影响进行了对比分析,得到了最佳的主轴承设计间隙,为曲轴主轴承的间隙设计提供了依据。     

浅析善后河枢纽工程云善船闸主体沉降规律

通过对云善船闸的定期观测和分析,获得船闸工程各部位的沉降情况,监控船闸的施工及使用状况。同时,根据沉降观测资料来分析沉降规律,探讨船闸变形的原因,为船闸施工和运行安全提供保证。