双洞公路隧道洞口废气污染影响的数值模拟

以双洞单向公路隧道洞口段气流为对象,采用k-ε双方程紊流模型及组分传输方程组,借助流体计算软件,从不同自然风条件、洞外段设置挡风壁和两隧道洞口不同相对位置(横向间距5～50 m)三个角度,数值模拟了出口废气的扩散情况,并相应得出对另一隧道入口污染的影响程度.研究结果表明,邻近隧道入口受出口废气污染的影响程度随不利风向的自然风速的减小以及两隧道洞口间距的增大而减小;洞外段合理的尺寸与形状的挡壁能有效减少甚至消除出口污染物扩散对其入口的影响.从而推出结论:对于特定隧道,洞口处的常年自然风的风向和风速大小与隧道通风效果息息相关;对于特定地形和特定自然风,可以通过选择适当的洞口间距来改善隧道的通风效果;如两洞口间距很近,则于洞口外两洞间设置挡风壁可有效提高两隧道的运营与防灾通风效果、降低废气污染程度.     

射流增压作用下分散排放隧道多风口通风特性及污染物控制研究

为揭示顶排风口进/排风引发的隧道压力突变对分散排放隧道多风口通风特性的影响，采用计算流体力学方法对射流增压作用下成组顶排风口的进排风规律进行模拟。结果表明：顶排风口排风/进风会造成隧道内局部压力的突增/突降，分散排放隧道多个顶排风口的通风特性受射流增压、沿程阻力和风口通风引发的压力突变作用。风口间距是影响多风口风量变化的重要因素。对于排风型风口，当风口间距较小时，上游风口排风产生的压力突增将超过风口间的沿程损失，下游风口由于静压提升而排风量沿程递增；当风口间距较大时，压力突增将不足以克服风口间的沿程损失，下游风口排风量沿程递减，甚至转变为进风；对于进风型风口，风口进风量将在进风引起的压力突降和隧道沿程损失的叠加作用下沿程递增。相较于其他风机开启方式，开启风机与风口组呈交错位置关系是分散排放隧道更为高效的通风控制方式，可使隧道污染物浓度极值最小。     

基于数值模拟-多元线性回归的大断面隧道平均瓦斯浓度检测位置研究

大断面隧道瓦斯浓度检测的不精确性会导致隧道绝对瓦斯涌出量实测值与真实值存在较大偏差，最终影响隧道瓦斯工区的划分，给隧道安全施工和成本控制带来巨大挑战。利用计算流体力学软件Fluent对隧道内部瓦斯分布规律进行模拟，通过正交试验定性分析断面宽度（A）、断面高度（B）、断面风速（C）对隧道断面平均瓦斯浓度的影响，并采用多元线性回归方法确定平均瓦斯浓度的最佳检测位置。研究表明，通风稳定条件下，隧道内部瓦斯呈稳定分布，且在隧道断面上会出现自上而下明显的分层分布；不同瓦斯工区条件下，断面宽度（A）、断面高度（B）、断面风速（C）对隧道断面平均瓦斯浓度影响的主次顺序存在差异；通过多元线性回归定量分析，得到不同瓦斯工区条件下稳定层流区域断面平均瓦斯浓度检测位置的计算模型。     

特长深埋高速公路隧道平导通风技术研究

针对越岭隧道由于大型山脉的阻隔而不便修建竖斜井的困境,文章以跨越天山的某特长深埋公路隧道为研究背景,提出了高速公路隧道平导运营通风方案。并通过大量的风网解算及通风系统总造价的正交设计分析,研究了特长深埋公路隧道取消斜竖井、采用平导进行通风的设计方法,分析了该隧道近远期通风机理和通风方案。结果表明:影响通风系统总造价的因素排序为:独立通风段长度、排风量、排风道面积、送风道面积;甄选的近远期通风方案很好地解决了较低交通量条件下高速公路隧道的运营通风难题;通风道长度达数公里的条件下,前段污风不宜全部从排风道排出,要充分利用大断面主隧道排风,减少能耗。     

高落差螺旋隧道运营期通风特性研究

为了研究螺旋结构隧道的通风特性,选取云南某高落差螺旋隧道为研究对象,对其不同工况下的隧道通风情况进行数值模拟分析。研究结果表明,从整体来看,隧道内的通风气流分布受隧道螺旋结构影响不大,但在每台射流风机的作用区域内,风速在隧道内外侧的纵向衰减特征并不相同,并会发生部分气流回流的情况。在火灾工况下,存在一段长约30 m的烟气逆流区,相比正常通风工况,火灾工况下的隧道内平均风速较大。     

世博会场馆处的一个噪声源--上海打浦路隧道3#排风塔噪声治理设计与效果

打浦路隧道3#排风塔位于世博会选址范围内,其噪声严重超标。通过采取消声、吸声、隔声等综合治理措施,使3#排风塔噪声对周边环境的夜间影响由65．7dB（A）降为50．2dB（A）。可供其它隧道风塔噪声治理及地铁排风口噪声治理参考。     

秦岭特长多竖井深埋隧道气温测试研究

文章依托秦岭终南山特长隧道,对隧道洞室内外气温、风速等气候条件进行了现场测试;研究隧道位置地层温度、洞内风速变化、外界气温变化等因素影响下,隧道内自然风速及洞内气温的变化范围和变化规律,可为多竖井深埋隧道通风防灾设计提供依据.     

新七道梁公路隧道运营通风效果测试及分析

文章通过对新七道梁公路隧道内外气温、风速等气象条件的现场测试,研究了在隧道区域范围内风速和气温等因素影响下,隧道内风速及洞内气温变化规律,可为新七道梁公路隧道营运过程中的通风控制,以及西北中高海拔地区公路隧道通风、消防、救援研究提供依据。     

八达岭地下站区间隧道火灾控制研究

采用FDS软件对八达岭地下车站相关隧道段的火灾工况进行三维数值模拟计算,结果是火灾强度为20 MW时隧道段的临界风速为3 m/s;采用一维数值模拟方法研究分析了火灾发生在隧道段不同位置时的通风方案,结果表明:合理的利用竖井内轴流风机,可以最大限度地减少隧道内射流风机的数量。     

公路隧道运营通风横通道周围流场特性研究

为研究公路隧道巷道式运营通风横通道周围的流场特性,以贵州凉风坳隧道为研究背景,利用流体力学研究软件Fluent建立隧道三维模型并进行了数值仿真计算。通过在隧道两边等风速条件下,对隧道内人行横通道以及车行横通道附近的流场特点研究,分析了运营通风横通道周围流场分布的具体特点。模拟结果表明:车行横通道与人行横通道两边流场分布基本相同;横通道内风速相对较小,约为隧道内风速的10%;不同风速下,横通道附近的速度分布和总压分布整体走势一致;两边流场相对稳定,不会进行风流和污染物的串流。     

The case for heterodoxy in longitudinal analysis

Longitudinal analysis should be developed with the prime objective of discovering the characteristics of dynamic, disequilibrium processes. This will require a range of different research methods, including qualitative social research, repeated cross-section surveys, panel surveys, aggregate time series analysis, and simulation models. In each case it is essential that models should be formulated in a dynamic way (e.g. with lags, inertia and asymmetry). Examples are given of work using each of these methods, applied to the analysis of habit, aging, market volatility, turnover, long-term demand elasticities, and forecasting using demographic information.     

公路隧道纵向通风的神经网络在线控制研究

针对单向交通的公路隧道采用射流风机进行纵向通风的特点,提出了采用神经网络在线控制的方法.利用该方法建立隧道通风在线控制模型,并结合空气动力学模型、污染模型及交通模型进行了隧道纵向通风过程的动态模拟仿真.结果表明,在公路隧道纵向通风中应用神经网络在线控制可以取得良好的效果.     

Assessing the effects of a mixed-mode design in a longitudinal household travel survey

The German Mobility Panel (MOP) is a national household travel survey, which has been collecting data on travel behavior in Germany since 1994. One of the MOP’s central assets is its ability to provide time-series data on travel behavior. Thus, the comparability of survey results from different years is a major objective of the survey method used. Declining survey participation rates in the last decade in various socio-demographic groups resulted in the implementation of a mixed-mode design for the MOP in 2013, both for the sampling stage (landline and mobile phone recruitment) and the data collection stage (paper and web). In this study, we analyze whether the adaptations in the survey mode do indeed improve the results and, if so, why and to what degree. Ideally, the survey mode adaptions have increased the representativeness of the MOP. However, measurement biases due to the mixed-mode design are also conceivable. To decompose survey mode effects, we applied the propensity score weighting method. This method imputes the hypothetical responses participants would have given in different survey modes; disparities between actual responses and hypothetical responses under another mode are then traced back to the mixed-mode design. Our analysis indicates that trip-rate biases on shopping, leisure, and short trips are partly caused by the mixed-mode design; in contrast, quantities of time spent in the transportation system, trips made by car and public transportation, and commuting trips are hardly biased.

     

高速公路单向交通隧道内最大纵坡设计研究

文章根据对隧道内施工运输、排水和通风等最大纵坡控制因素的分析,提出了隧道内单向交通连续上坡路段最大纵坡的建议值,以及长大隧道内增大坡度的技术措施,可供公路设计参考和借鉴。     

运营公路隧道空气污染物纵向分布的数值模拟

文章通过建立单向行驶隧道空气污染物浓度分布的对流-扩散一维有限差分方程,并利用隧道内交通流仿真的结果,得出了污染源项的离散形式.在进行交通流仿真的同时,实时地求解该差分方程,从而确定隧道内污染物浓度沿纵向的分布规律.对仿真结果的分析表明,交通流对隧道内空气污染物浓度分布有极大影响,其结果可为研究隧道空气污染的扩散提供重要依据.     

E-bike user groups and substitution effects: evidence from longitudinal travel data in the Netherlands

Transportation - In recent years, the e-bike has become increasingly popular in many European countries. With higher speeds and less effort needed, the e-bike is a promising mode of transport to...     

Activity space estimation with longitudinal observations of social media data

In this paper, we demonstrate the use of an inexpensive and easy-to-collect long-term dataset to address the problems caused by basing activity space studies off short-term data. In total, we use 63,114 geo-tagged tweets from 116 unique users to create individuals’ activity spaces based on minimum bounding geometry (convex hull). By using polygon density maps of activity space, we found clear differences between weekday and weekend activity spaces, and were able to observe the growth trajectory of activity space over 17 weeks. In order to reflect the heterogeneous nature of spatial behavior and tweeting habits, we used Latent Class Analysis twice. First, to identify five unique patterns of location-based activity spaces that are different in shape and anchoring. Second, we identify three unique growth trajectories. The comparison among these latent growth trajectories shows that in order to capture the extent of activity spaces we need long time periods for some individuals and shorter periods of observation for others. We also show that past studies using a single digit number of weeks may not be sufficient to capture individuals’ activity space. The major activity locations identified using a multilevel latent class model, do not appear to be statistically related to the growth patterns of Twitter users activity spaces. The evidence here shows Twitter data can be a valuable complementary source of information for heterogeneity analysis in activity-based modeling and simulation.     

公路隧道纵向送排式通风竖井数量及其间距研究

近年来,随着纵向通风技术的成熟,越来越多的长大隧道采用竖井送排式纵向通风方式,这种通风方式首先要确定竖井的数量及其间距。文章根据隧道内通风时对于断面风速的限制要求,提出了相同坡度下长大隧道竖井数量的计算方法,分析了隧道路面坡度对于竖井间距的影响,得到了不同坡度下隧道长度的折算方法及竖井间距计算方法,并给出了实例分析,其研究结果可以应用在长大隧道的相关设计研究中。     

Using longitudinal methods for analysis of a short-term transportation demonstration project

This paper documents an application of panel, or longitudinal data collection in the evaluation of a TSM (Transportation Systems Management) demonstration project. The project was a four-week demonstration of staggered work hours in downtown Honolulu during February–March 1988. The 4 wave panel survey elicited commuting experiences of approximately 2,000 downtown employees at two week intervals before and during the project. The sample involved both employees who participated in the project by shifting their work hours, and those who did not. The panel survey was augmented by floating-car observations of travel times on major routes into downtown Honolulu on the same four dates.The purpose of the analysis was to determine whether employee commute times were affected, and if so, how these changes were distributed among various employee segments. Two methods were used. First, travel time changes were estimated using paired t-tests. Second, regression equations were used to estimate project time savings as a function of trip length, route, and location of residence. Results show that travel time savings due to the project were typically small, less than ten percent. Nonparticipants experienced greater savings than participants, and some segments of participants experienced longer travel times during the project. The panel method proved to be an effective way to measure project travel time impacts and shows that the method is appropriate in short time applications.Presented at the Annual Meeting of Transportation Research Board, January 7–11. 1990, Washington, D.C.     

旧路加宽路面纵向开裂原因分析与防治

针对公路改建工程中出现的沥青路面纵向开裂这一常见现象,结合省道改建工程的设计特点与施工要点,重点就加宽路基部位与路面各结构层的施工质量控制方面进行分析和阐述,提出施工控制方法及相应的处理措施。