穿越易滑岩层小净距隧道开挖与量测控制要点

在我国中西部铁路扩建复线工程中,由于地质条件限制,不得不穿越滑坡区段,新建隧道施工时易引起隧道变形与滑坡体变形.小净距隧道是双洞隧道净距介于连拱隧道与规范要求上下行分离式隧道最小净距之间的一种特殊隧道结构形式,由于隧道净距小,施工时双洞相互影响较大,对隧道围岩,特别是中夹岩岩体稳定性有很大的影响.因此,探讨安全、合理、经济的高速公路小净距隧道施工方法十分必要.     

高速公路隧道扩建力学分析及方案研究

若原有隧道为双洞四车道分离式隧道,可在原有隧道附近新建双洞,将现有的隧道变为四洞八车道的小净距隧道群。新建隧道时,隧道周围的围岩应力场已经历过多次演变,并会在施工过程中以此为基础再进行多次演变。这种应力的多次改变会导致既有隧道在原有应力场基础上的受力变异,以及新建隧道的受力变异,从而使新建隧道和既有隧道产生复杂的安全性问题。结合某高速公路隧道扩建工程实例,通过分析,确定了其扩建型式及隧道开挖方案,为今后隧道扩建工程的设计、施工提供了科学依据并积累了经验。     

基于数值模拟分析的高速公路上跨高铁隧道方案研究

河南西部某高速公路改扩建工程在下穿的客运专线铁路上方施工,考虑施工及运营状态下隧道的安全,采用强度折减法对高速公路扩建前、扩建中及扩建后的隧道结构安全度进行了研究,同时对其防护措施及相应的效果加以探讨,以便为类似工程方案的选择提供借鉴。     

小净距隧道开挖方法浅论

小净距隧道是介于普通隧道和连拱隧道之间的一种隧道结构形式,正以其独特的优点引起了隧道界的关注.文章论述了间距为5 m左右的小净距隧道的围岩特点、开挖方法及工程实例.     

山区公路既有隧道扩建设计探讨

山区公路隧道在改善公路线型、缩短里程、保护生态环境等方面起着重要作用。文章结合内龙隧道扩建设计实例,分析了新建隧道设计和扩建隧道设计的差异,探讨了既有隧道扩建设计中需考虑的重点因素与隧道洞口、结构、防排水设计及岩溶处理方法,为今后类似隧道扩建设计提供参考。     

隧道原位扩建CD工法地表沉降预测研究

近年来,越来越多的隧道面临改扩建问题,隧道扩建工程往往呈现出大断面、小净距、隧道群等特点,而原位扩建隧道的地表沉降规律也呈现出自身的特性:地表沉降槽曲线沿隧道中心线不对称、存在局部突变值等.对泉厦高速公路大帽山隧道原位扩建工程采用CD工法施工引起的地表沉降实测规律分析,基于Peck公式及叠加原理,提出了适用于隧道原位扩建施工产生的地表沉降的简便预测函数关系式,并验证了函数关系式的适用性.应用研究表明:该函数关系式能正确反映隧道原位扩建施工地表沉降规律,计算值与实测结果较为吻合.研究成果为隧道原位扩建工程地表沉降的预测提供了新的思路与方法.     

超小净距隧道结构设计与施工稳定性分析

文章依托某城市地下互通式隧道工程中一处超小净距隧道工程,对超小净距隧道的三种结构形式进行比选,研究确定了无中隔墙的超小净距隧道结构方案,采用锚杆注浆加固中夹岩柱并加强一次衬砌和微震预裂爆破技术的分步挖掘施工方案;利用有限元数值模拟超小净距隧道支护施工过程,得到其各个施工步序下围岩及支护结构应力、应变状态,分析其稳定性,优化并验证设计参数,有效指导设计与施工。     

城市地下立交隧道交叉口施工方法研究

城市立交隧道施工的难点在于两条隧道合并为一条隧道的交叉口施工,该处存在特大断面隧道、偏连拱隧道和小净距隧道型式的多重转换,施工风险高,对工法、工艺要求苛刻。文章以杭州市紫之隧道的地下立交交叉口工程为依托,提出了一种小洞开大洞,然后再横向开挖,最后反向开挖的施工方法和施工工序。结合工程特点,采用有限元数值模拟和监控量测方法验证了该施工方法的合理性。结果表明:对隧道交叉口采用导洞爬坡反向施工方法可以保证分叉段施工安全,解决小洞往大洞方向开挖的难题;分叉隧道开挖过程中,围岩所受拉应力主要集中在拱顶、拱底及中间岩柱上,所受压应力主要集中在中间岩柱及大拱拱腰、小净距外侧拱腰处;衬砌结构最大拉应力出现在拱底,最大压应力发生在拱腰处。     

小间距大跨隧道施工引起地层变形规律及支护结构受力特征研究

小间距隧道施工引起的地层变形与两隧道间净距有很大关系,净距很小时,不能简单看作两个独立隧道施工引起地层变形的叠加.基于厦门机场路隧道小间距段为工程背景,采用有限差分程序(FLAC30)模拟分析了隧道间净距对地层变形和支护结构受力的影响,并通过实测数据分析了隧道开挖引起地层变形的横向影响范围,对工程的后续施工提供了指导,为大跨度小间距隧道的开发和施工设计提供了较确切的参考数据和理论依据.     

软弱围岩中大跨度小净距隧道爆破振动监测与分析

沈海高速公路泉州-厦门段扩建工程中隧道部份均采用小净距布置型式,隧道爆破将对既有隧道的围岩,尤其是对中夹岩稳定性造成较大的影响。为确定合理的爆破装药量以确保临近隧道围岩在爆破振动时的稳定性,通过现场监测,得到了软弱围岩中隧道爆破围岩的振动速度历时曲线和爆破地震波在小净距隧道中夹岩中的传播规律,并提出了确保工程稳定的合理装药量,研究成果为工程的设计与施工提供了科学依据。     

Support Form and Construction Sequence for Soft Rock Tunnels with Small Spacing,High Stress and Deformation北大核心CSCD

Increasingly, stations are being extended to tunnels due to the effects of topography on mountain rail-ways and the requirements of the stations. A forked tail tunnel arrangement is the most popular one, but the concomi-tant effect of the following tunnel on the antecedent tunnel during construction of a tunnel with small spacing causes cracking of the primary support and secondary lining as well as heaving of the invert, which continues to trouble en-gineers. Different problems are encountered by different tunnels because of the complexities and variations of geo-logical environments. Using the construction of two single-line sections with small spacing for the Xinchengzi tunnel on the Lanzhou-Chongqing railway as an example, the support form for a soft rock tunnel with small spacing and high geostress and deformation, as well as the invert construction sequence of the left and right lines and secondary lining, are analyzed and discussed. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

相邻隧道扩挖施工影响分析

采用现场实测和数值计算方法,对乌鞘岭志留系地层板岩夹千枚岩地段左线隧道扩挖施工引起右线隧道的围岩状况和既有支护结构的受力变化进行分析。结果表明,两相邻隧道在不同施工阶段进行导洞开挖和扩挖前后存在一定程度的群洞效应作用,扩挖施工引起右线隧道向左线隧道产生了较小的侧移;在左线隧道扩挖后,右线隧道既有衬砌的接触压力、结构轴力和弯矩均有明显增大,但衬砌结构的安全系数均满足规范要求,处于安全状态。     

复杂环境超小间距隧道盾构掘进施工技术北大核心CSCD

针对浅埋超小间距隧道盾构施工,文章以特拉维夫红线轻轨工程西标段双线盾构施工为工程背景,从隧道加固施工、盾构掘进控制、监测控制与应急管理等方面进行系统研究。结果表明,加固施工在小间距盾构隧道施工中至关重要,可有效降低隧道施工风险;对未加固的小间距盾构隧道施工,应保持土压平稳,加强土压精细化控制;严格控制出渣量,做好渣土改良,控制土体损失率低于0.3%;在盾壳外部注入膨润土或克泥效,可有效地减少邻近隧道的位移量;应结合实时监测数据,控制回填注浆量及注浆质量;隧道施工过程应加强对邻近既有建筑物的监测。     

On some experimental features of car-following behavior and how to model them

We have carried out car-following experiments with a 25-car-platoon on an open road section to study the relation between a car’s speed and its spacing under various traffic conditions, in the hope to resolve a controversy surrounding this fundamental relation of vehicular traffic. In this paper we extend our previous analysis of these experiments, and report new experimental findings. In particular, we reveal that the platoon length (hence the average spacing within a platoon) might be significantly different even if the average velocity of the platoon is essentially the same. The findings further demonstrate that the traffic states span a 2D region in the speed-spacing (or density) plane. The common practice of using a single speed-spacing curve to model vehicular traffic ignores the variability and imprecision of human driving and is therefore inadequate. We have proposed a car-following model based on a mechanism that in certain ranges of speed and spacing, drivers are insensitive to the changes in spacing when the velocity differences between cars are small. It was shown that the model can reproduce the experimental results well.     

小净距隧道群控制爆破技术

文章通过对大坪山隧道的工程概况、地形地质特点及工程施工难点的分析,并借助数值研究手段,有针对性地提出了YYK393+581~YYK393+621洞段中导洞超前、大断面循序跟进的施工方法;研究分析了炸药性能及尺寸等控制爆破技术要点及爆破参数,同时就施工安全措施提出了一些建议。     

紫坪埔隧道小净距段施工方案模型试验研究

为节约工程造价,董家山隧道汶川端设计为渐变小净距隧道与整幅修建的泯江大桥相接。该端隧道洞口段左、右线间距较小,围岩较差。为保证隧道的安全施工,利用模型试验对洞口小净距段岩墙的加固措施、开挖方式及支护体系等施工方案进行了研究,提出了该段合理的施工方法和岩墙加固措施的建议,为董家山隧道小净距段的顺利施工提供指导。     

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。     

富水区隧道环向盲管间距优化分析北大核心CSCD

富水区隧道涌水遵循“以堵为主、防排结合”的处置原则,其中排水体系构建的合理性是隧道安全施工与良好运营的关键因素。首先分析隧道排水体系,揭示其工作原理,然后利用FLAC 3D有限差分软件,对鸿图特长隧道富水断层区设置的不同环向盲管间距进行三维流固耦合模拟,通过分析渗水压力、锚杆受力及涌水量,揭示塑性区体积及分布区域特征。研究结果表明:沿隧道轴向,支护结构孔隙水压力大致呈周期性分布,其周期近似等于环向盲管纵向间距;加密环向盲管,在降低支护结构受力并减小塑性区体积的同时,会增加隧道排水量;随环向盲管间距的增大,注浆加固圈塑性区首先出现在围岩好的区域,断层区出现塑性区最晚;断层区锚杆加固效果较差,可通过减小钢拱架环向间距以提高结构刚度,使注浆加固圈沿轴向受力更合理。综合考虑各种因素,建议在建工程断层区环向盲管间距设置为3 m,断层附近区间距为4 m。     

Optimal stop spacing and headway of congested transit system considering realistic wait times

Abstract

This paper revisits the classical transit scheduling problem and investigates the relationship between stop spacing and headway, considering realistic wait time and operable transit capacity. Headway and stop spacing are important determinants for planning a transit system, which influence the service level as well as the cost of operation. A mathematical model is developed, and the objective function is user travel time which is minimized by the optimized stop spacing and headway, subject to the constraints of operable fleet size and route capacity. Optimal stop spacing and headway solutions are obtained in a numerical example. Sensitivity analysis is conducted, and the effect of model parameters on user travel time is explored.     

An experimental comparative study of autonomous and co-operative vehicle-follower control systems

This paper is a comparative study of the performance of constant-time-gap autonomous control systems and co-operative longitudinal control systems that use inter-vehicle communication. Analytical results show that the minimum time gap that can be achieved in autonomous control is limited by the bandwidth of the internal dynamics of the vehicle. Experimental results from typical sensors and actuators are used to show that in practice it is very difficult to achieve a time gap less than 1 s with autonomous vehicle following. This translates to an inter-vehicle spacing of 30 m at highway speeds and a theoretical maximum traffic flow of about 3000 vehicles per hour. The quality of radar range and range rate measurements pose limitations on the spacing accuracy and ride quality that can be achieved in autonomous control. Dramatic improvements in the trade-off between ride quality and spacing accuracy can be obtained merely by replacing radar range rate in the autonomous control algorithm with the difference between the measured velocities of the two cars (a rudimentary form of co-operation). As a baseline comparison, the experimental performance of fully co-operative control is presented. An inter-vehicle spacing of 6.5 m is maintained in a platoon of 8 co-operative vehicles with an excellent ride quality and an accuracy of ±20 cm. Extending this to a 10-vehicle platoon makes it possible to achieve theoretical maximum traffic flows of about 6400 vehicles per hour.Another issue of importance addressed in the paper is the need to accommodate malfunctions in radar (ranging sensor) measurements. Measurement errors can occur due to hardware malfunctions as well as due to road curves, grades and the highway environment in the case of large inter-vehicle spacing. The ability of a co-operative control system to monitor the health of the radar and correct for such errors and malfunctions is demonstrated experimentally.