双洞小净距隧道施工控制要点

在现行的隧道设计施工规范中,还没有明确规定小净距隧道的设计、施工规程.文章结合工程实例介绍了小净距隧道的开挖顺序和围岩支护加固方式,以及中央岩柱加固、监控量测等关键工序,对小净距隧道施工质量的控制作了初步探讨.     

地铁隧道压底注浆研究

在地铁隧道现场注浆试验的基础上,研究了压底注浆机理,讨论了压底注浆设计、施工要点,比较了注浆后隧道隆起的计算方法;利用现场实测隧道变形资料,通过反馈分析确定了注浆等效压力的经验公式,对地铁隧道下方压底注浆设计与施工有一定的指导意义。     

活断层错动位移下衬砌断面型式对隧道结构的影响

以棋盘石隧道为工程背景,采用有限元方法,设置五种不同仰拱半径的三心圆断面,对比研究了活动断层错动下不同衬砌断面型式对链式结构隧道受力及塑性变形的影响。结果表明:断层错动引起隧道二次衬砌受到拉张、剪切、挤压组合作用;断层错动引起的高应力带主要在断层带内的节段拱脚位置,且峰值位于上盘,剪切缝能有效地吸收断层错动产生的拉应力;在隧道断面不断趋向正圆的过程中,二次衬砌最大主应力、最小主应力、剪应力均呈减小趋势,等效塑性应变呈增大趋势。     

大循高速公路桥梁钢筋施工中镦粗直螺纹套筒连接法标准化施工工艺

墩粗直螺纹套筒连接接头,强度高、螺纹精度高、质量稳定、容易控制等优点,在大循项目上得到推广。     

The influence of parents’ travel patterns,perceptions and residential self-selectivity to their children travel mode shares

Using the UK National Travel Survey from 2002 to 2006, this paper investigates the influence of households’ residential self-selectivity, parents’ perceptions on accessibilities and their travel patterns on their children daily travel mode share. In doing this, this study introduces a model structure that represents the complex interactions between the parents’ travel patterns, their perceptions on public transport services and their reported residential self-selectivity reasons and the children travel mode shares. This structure is analysed with structural equation modelling. The model estimation results show that parents’ residential self-selectivity, parents’ perceptions and satisfactions on accessibilities and their daily travel patterns significantly influence the children’s daily travel mode shares. However, the effects are not uniform across household members. This study has revealed that households’ residential self-selectivity behaviours have more correlations with the children’s non-motorised mode shares, whilst the parents’ perceptions and satisfactions on transport infrastructure and public transport service qualities have more correlations with parents’ mode shares. The results also confirm that parents’ non-motorised modes use in travelling is highly correlated with the children’s physically active travel mode shares. However, at the same time, the results also show that the effects of mothers’ car use to the children travel mode shares is more apparent than fathers’.     

Modeling traffic operation at signalized intersections without explicit left‐turn yielding rules with an enhanced cell transmission model

This paper presents an enhanced cell transmission model (CTM) to capture traffic operation at signalized intersections without explicit permissive left‐turn yielding rules (i.e. aggressive permissive left‐turn maneuvers may not necessarily yield to opposing through traffic), which can be widely observed in many developing countries. Different from previous studies that focus on traffic dynamics on approaching links, this study contributes to modeling traffic operations within the intersection. A novel cell transmission framework with various types of virtual cells is proposed to model the dynamics of traffic movements from approach to exit. The unique phenomenon of competitive occupying of the conflict point between the left turn and opposing through movements is modeled. The cell state indicating its blockage is proposed to capture the dynamic queue formulation and dissipation and to evaluate the operational traffic performance at the intersection. Field validation results show that the proposed model can capture the operation of traffic at signalized intersections without explicit permissive left‐turn yielding rules with significantly higher level of accuracy than traditional traffic flow models. Copyright © 2016 John Wiley & Sons, Ltd.     

浅埋暗挖平顶多跨地下商场施工技术

深圳中信地下商场位于城市繁华地段,地面交通繁忙、地下管线密布,工程地质、水文地质条件复杂,因此采用了以浅埋暗挖和洞内加固为主的施工技术.文章重点介绍了超大管棚预加固技术、开挖方法的研究及优化、二次衬砌的体系转换及监控量测,对其他城市地下空间的开发具有一定的借鉴价值.     

可拓理论在高等级公路隧道围岩分级中的应用研究

根据可拓理论在解决不相容问题及不确定问题等方面的突出特点,文章对其进行了适当的改进,得出高等级公路隧道围岩分级系统可拓评价体系,并应用于广东省惠深高速公路牛湖山隧道的围岩质量评价当中.且通过与灰色关联分析方法、专家经验方法等评价结果相比较,证明了高速公路隧道围岩分级系统可拓评价体系的科学性、合理性和经济性.     

基于PHA-LEC-SCL法公路隧道施工安全评价研究

为了制定科学的公路隧道施工安全评价的基本模式,针对公路隧道施工的危险、有害因素的危害程度及特殊工艺,将公路隧道施工系统分为隧道开挖、爆破、施工用电、施工通风、出碴与洞内运输、支护衬砌等6个主要子系统.运用预先危险性分析法(PHA)对公路隧道施工的危险、危害因素进行辨识和定性分析,结合作业条件危险性评价法(LEC)对公路隧道施工系统中各子系统进行危险性评价,定量分析计算PHA中的子系统各个危险因素的危险等级,并采用安全检查表(SCL)对公路隧道施工现场进行安全综合评价,建立了安全评价方法之间的内在联系.PHA-LEC-SCL法确立了公路隧道施工安全评价的基本模式.     

Existence of self-financing and Pareto-improving congestion pricing: Impact of value of time distribution

This paper considers a static congestion pricing model in which travelers select a mode from either, driving on highway or taking public transit, to minimize a combination of travel time, operating cost and toll. The focus is to examine how travelers’ value of time (VOT), which is continuously distributed in a population, affects the existence of a pricing-refunding scheme that is both self-financing (i.e. requiring no external subsidy) and Pareto-improving (i.e. reducing system travel time while making nobody worse off). A condition that insures the existence of a self-financing and Pareto-improving (SFPI) toll scheme is derived. Our derivation reveals that the toll authority can select a proper SFPI scheme to distribute the benefits from congestion pricing through a credit-based pricing scheme. Under mild assumptions, we prove that an SFPI toll always exists for concave VOT functions, of which the linear function corresponding to the uniform distribution is a special case. Existence conditions are also established for a class of rational functions. These results can be used to analyze more realistic VOT distributions such as log-normal distribution. A useful implication of our analysis is that the existence of an SFPI scheme is not guaranteed for general functional forms. Thus, external subsidies may be required to ensure Pareto-improving, even if policy-makers are willing to return all toll revenues to road users.