永福屯隧道马头门施工工艺分析

隧道施工中,若遇到各种设备房与隧道主洞交差较为复杂的情况,采用马头门施工工艺能较好保障施工过程中的洞体稳定安全。文章结合永福屯隧道工程实例,介绍了马头门施工工法及其优点,分析了其施工质量控制措施。     

大台竖井马头门段施工技术

文章根据兰新线兰武段乌鞘岭隧道大台竖井工程地处F7断层影响带内的马头门段的施工经验,通过实例简要地介绍了深竖井的设计、施工技术.     

岩脚一号隧道病害原因分析及处理

内昆线岩脚一号隧道位于一巨型岩堆体内,隧道在施工期间曾出现山体位移、开裂和下沉,洞内出现衬砌开裂和坍方冒顶.文章详细叙述了病害产生的原因和相应的处理措施,并采用有限元程序和条分法对整个岩堆体的稳定性进行了分析检算.     

某隧道初期支护混凝土开裂处理及效果分析

文章结合某高速公路隧道工程初期支护开裂处理情况,分析了初期支护混凝土的开裂原因,以及采用的洞内小导管注浆加固裂缝区、加强开裂区监控量测等处理措施及效果。工程实践表明,经过处理后的隧道周边收敛和拱顶下沉量均在规范允许范围内,取得了良好的效果,为今后类似软弱围岩隧道施工积累了经验。     

公路隧道穿越浅埋断层破碎带工程处理技术

成(都)简(阳)快速路龙泉山一号隧道进口段施工穿越浅埋断层破碎带时揭示围岩破碎、地下水较发育,施工期间发生了喷混凝土掉块、钢架扭曲变形、拱部下沉、地表开裂等危害,严重影响了隧道结构质量及安全运营.针对发生的初期支护变形及沉降的主要原因,设计中采用了微台阶开挖工法,以及加大预留变形量、设置大拱脚、围岩注浆加固、拆换原支护等处理措施,取得了良好的施工效果.     

扎果隧道洞口浅埋段大变形的处理措施探讨

高海拔高寒地区隧道施工过程中存在诸多不确定的影响因素,会出现浅埋段地表开裂、塌陷及洞内大变形等。由于高原地区地质情况复杂多变,施工风险高,遇到软弱富水、浅埋偏压、反复冻融等围岩时容易造成初期支护拱架下沉或变形,当下沉量或变形量超过预留量侵入二衬净空时,须对侵限拱架进行置换处理。为了使得高原隧道施工的安全质量和施工进度得到保障,本文以花久公路扎果隧道洞口浅埋段为例,对隧道浅埋段大变形处理进行施工技术方面进行研究分析,以期为类似工程地质条件下的隧道洞口段大变形处理提供一定的指导。     

公路隧道穿越软弱围岩的变形与控制方法

公路隧道穿越软弱围岩时,其施工难点往往是如何将围岩变形、初期支护拱顶下沉和水平收敛位移控制在允许范围内,处理不当将造成结构开裂、变形以及初期支护侵入二次衬砌甚至坍方等病害.从国内施工现状与存在的问题入手,分析了引起隧道大变形的原因,总结出控制隧道大变形的两大关键点:一是选择合适的施工方法,二是要采取有效控制沉降的措施.并重点针对拱部核心土台阶法提出了控制沉降的措施,包括施工原则贯彻始终、横断面开挖合理分步、控制施工进尺及台阶长度、施作锁脚锚杆和垫块、合理处理渗水和施工用水、减少地基扰动、清除虚碴、加强施工动态管理等几个方面.     

厦门翔安海底隧道CRD法中各施工部对拱顶下沉的影响分析

文章以厦门翔安海底隧道陆域段软弱地层大断面浅埋隧道CRD法施工为工程背景,结合现场位移监控量测和实际施工情况,对不同开挖顺序下CRD法中各施工部对拱顶下沉的影响进行了分析研究。研究结果表明,翔安隧道CRD法拱顶下沉为台阶状上升曲线,最后趋于稳定;各分部开挖引起的拱顶下沉量具有一定的比例关系,可用于对最终拱顶下沉量的预报和控制指示;各分部仰拱及时闭合是控制最终下沉量的关键;采用CRD1、3部超前施工比CRD1、2部超前对控制拱顶下沉较为有利;施工中应重点监测和控制最早开挖的CRD1部拱顶下沉。     

平阿高速公路黄土区涵洞病害特征调查及防治对策探讨

涵洞病害是高速公路在黄土区域中典型病害之一,也是高速公路在运营期间的重点维护和防治对象。本文针对青海省境内平阿高速公路在穿越黄土区域段的51座涵洞进行了实地调研,基于此总结了青海省黄土地区平阿公路涵洞出现的7种典型病害类型,即涵洞下沉、基础开裂、护锥翼墙沉降开裂或倾斜错位、涵节错位或填缝脱落、内部或进出口积水淤塞、涵背填土塌陷、涵顶路面开裂等。对涵洞的基本病害特征进行了分析,并对不同病害类型提出了相应的防治对策与建议。该研究成果可以加深对黄土区公路涵洞病害机理的认识,对黄土地区高速公路涵洞病害的勘察、防治和施工具有一定的指导意义。     

悬索桥重力式锚碇沉井基础下沉施工监控技术

为研究悬索桥重力式锚碇沉井基础下沉施工监控技术,保障沉井基础下沉施工质量与安全,文章基于某地区悬索桥重力式锚碇沉井基础结构,选取沉井基础结构应力、刃脚踏面应力、侧壁土压力等作为施工监控项目,通过设置下沉施工监控点,获取沉井基础下沉施工监控数据,分析沉井基础下沉施工情况。结果表明：沉井基础结构应力与沉井基础下沉施工深度成正比;刃脚踏面应力在第4节下沉施工完成后达到应力最大值为134 MPa;当下沉施工深度为11.5 m时,沉井基础侧壁土压力达到最大值;沉井基础几何姿态的监控误差较小。该技术可助力悬索桥重力式锚碇沉井基础下沉安全施工。     

Street characteristics to encourage children to walk

An experiment tested whether physical disorder affected low to moderate income African–American children’s choice of street to walk on and their parents’ choice of a street for them to walk on. The experiment used an innovative desktop simulation in which 32 fourth and fifth grade African–American children and 30 parents viewed and explored pairs of virtual walk-through streets manipulated on disorder (across three contexts and two other street and sidewalk characteristics) and picked from each pair the one to walk on (child) or for the child to walk on (parent). Each participant was asked to report the reasons for the choices. The analysis revealed that children and their parents were more likely to walk (or have the child walk) on streets lower in disorder. Reported reasons for choices confirmed the importance of physical disorder in affecting walking choices. Low-cost improvements in order may make streets more desirable for recreational walking.     

How to obtain a healthy journey to school

Danish children walk and cycle a lot and at the same time have one of the best child road safety records in the western part of world. Based on several studies, the paper describes how Denmark has obtained a good child road safety and why Danish children choose to walk and cycle. Child road safety has predominantly been improved due to higher seat belt use and many implemented local safety measures such as campaigns and physical safe routes to school projects. It is mostly safe routes to school projects that include speed reducing measures and signalisation of junctions that are successful. The distance from home to school is an important factor in children’s transport mode choice. Since about half of Danish children have less than 1.5 km to school the decentralised school structure with many fairly small schools is an important reason to the many walking and bicycle journeys. Road design and motorised traffic volumes do influence children’s mode choice, but to a rather limited extent.     

Factors influencing the propensity to cycle to work

This paper describes the development of a mode choice model for the journey to work with special emphasis on the propensity to cycle. The model combines Revealed Preference (RP) and Stated Preference (SP) data to form a very large and comprehensive model. RP data from the National Travel Survey was combined with a specially commissioned RP survey. A number of SP surveys were also undertaken to examine the effects of different types of en-route and trip end cycle facilities and financial measures to encourage cycling.The development of the model is described in detail. The model was used to forecast trends in urban commuting shares over time and to predict the impacts of different measures to encourage cycling. Of the en-route cycle facilities, a completely segregated cycleway was forecast to have the greatest impact, but even the unfeasible scenario of universal provision of such facilities would only result in a 55% increase in cycling and a slight reduction in car commuting. Payments for cycling to work were found to be highly effective with a £2 daily payment almost doubling the level of cycling. The most effective policy would combine improvements in en-route facilities, a daily payment to cycle to work and comprehensive trip end facilities and this would also have a significant impact on car commuting.     

听哲学家讲授成功的秘诀

相信自己是一只雄鹰 一个人在高山之巅的鹰巢里抓到一只幼鹰,他把幼鹰带回家养在鸡笼里.这只幼鹰和鸡一起啄食、嬉闹和休息.它以为自己是一只鸡.     

Are consumers willing to pay to let cars drive for them? Analyzing response to autonomous vehicles

Autonomous vehicles use sensing and communication technologies to navigate safely and efficiently with little or no input from the driver. These driverless technologies will create an unprecedented revolution in how people move, and policymakers will need appropriate tools to plan for and analyze the large impacts of novel navigation systems. In this paper we derive semiparametric estimates of the willingness to pay for automation. We use data from a nationwide online panel of 1260 individuals who answered a vehicle-purchase discrete choice experiment focused on energy efficiency and autonomous features. Several models were estimated with the choice microdata, including a conditional logit with deterministic consumer heterogeneity, a parametric random parameter logit, and a semiparametric random parameter logit. We draw three key results from our analysis. First, we find that the average household is willing to pay a significant amount for automation: about $3500 for partial automation and $4900 for full automation. Second, we estimate substantial heterogeneity in preferences for automation, where a significant share of the sample is willing to pay above $10,000 for full automation technology while many are not willing to pay any positive amount for the technology. Third, our semiparametric random parameter logit estimates suggest that the demand for automation is split approximately evenly between high, modest and no demand, highlighting the importance of modeling flexible preferences for emerging vehicle technology.     

Instructions to Authors

Instructions for Authors

Instructions to Authors     

Instructions to authors

Instructions for Authors

Instructions to authors     

Instructions to authors

Instructions for Authors

Instructions to authors