Improving the existing roadway tunnels capacity by adding new tunnels—a structural approach

The roadway tunnel is considered a good solution for the success of modern roadway networks. It can help to overcome possible traffic congestion and considerably reduce journey time. The continuous growth of traffic volumes leads to increase congestion and decrease safety. This leads to the need for extra tunnel space. The extra tunnel space can be achieved either by the widening of the existing tunnel or by adding a new one. The choice of the suitable method is dependent on many factors like tunnels alignment, site conditions, construction method, tunnel operation, risk assessment…etc. The current research investigates the second alternative through a specific case study as an example. The method comprises adding two new tunnels to an existing twin roadway tunnels. The investigated problem considers the new tunnels to be added vertically or horizontally. The influence of the new tunnel construction on the existing tunnels is investigated considering both the variation of relative position and spacing distance in a parametric study context. Several numerical models are employed to check the construction sequence and the tunnelling safety. These models are used to evaluate the induced stresses in surrounding ground for two different soil types, straining actions in tunnels’ liner and deformations of both ground and liner. The result demonstration shows how to find out the minimum practical and safe spacing distance between the driven new tunnels and the existing ones without the need for the relatively expensive soil strengthening techniques.     

不同围岩类别小间距隧道施工过程模拟研究

从不同围岩类别出发,对3车道小间距隧道采用典型双侧导坑法的开挖施工过程进行了数值模拟研究。给出了不同围岩类型下的3车道小间距隧道在施工过程中的围岩破坏特征及其变形规律和变形规律的相似性,获得了洞周最大变形量值之间的相对比值关系。通过中隔墙的变形与塑性破坏规律分析,比选出了3车道隧道中隔墙最小间距的工程设计参考值。分析表明：II类围岩合理间距不应小于0.45B,III类围岩应在0.35～0.45B之间,IV,V类围岩可在0.2～0.35B之间选择,对信息化反馈施工,指出了必须重点监控与关注的位置。为小间距隧道的发展和施工设计提供了较确切的参考数据和理论依据。     

Interaction between two parallel tunnels

A series of finite element analyses were performed to study the behaviour of a system of two parallel and adjacent tunnels. Various sequences of excavation of the two tunnels and installation of tunnel liners have been simulated in the analyses. Influence of various parameters on the behaviour of the two parallel tunnels has been investigated. The important parameters considered in this study are: the width of the pillar separating the two tunnels; the tunnel depth; support condition; sequence of excavation; and, to some extent, the influence of plastic yielding in the medium surrounding the two tunnels.     

Traffic-related immissions and their impact on historic buildings: implications from a pilot study at two German cities

Besides the enormous improvement of air quality in Germany due to the reduction of sulphur dioxide emissions in the last decades, high immissions of nitrogen oxides and fine particulate matter are frequently observed at traffic-rich urban sites. The changed chemical composition of air pollution requires a new investigation of its impact on historic buildings constructed of natural stone. In a pilot study a multi-disciplinary approach was chosen to obtain information on the actual pollution situation of historic buildings and monuments at traffic hotspots in Germany. The study concentrated on the two German cities of Munich and Mainz of different size, traffic volume and stone inventory. Dose–response functions were calculated to demonstrate the change of impact of different pollutants over the last three decades, and for comparison of traffic hotspots and housing areas of both cities. Numeric modelling on a city-scale was used to identify the historic buildings and monuments affected by elevated traffic immissions. Because a relevant part of these pollutants is dominated by short-range transport, the differences of wind speed and deposition rates were calculated using a street-scale 3D flow and dispersion model regarding traffic volume, wind regime and adjacent buildings. Finally, particulate matter was sampled at different positions of two buildings heavily exposed to traffic emissions. Individual particles were investigated by environmental scanning electron microscopy. After classification of the particles into different chemical groups, the fraction of traffic-induced particulate matter was quantified. Summarizing the results, it must be stated that soiling by traffic-related particulate matter, deposition of nitrates deriving from exhaust emission and other diffusely emitted components bear a severe damage potential for natural building stone at least locally at traffic-rich urban sites.     

穿越东非大裂谷内马铁路隧道的抗震分析及断层位错设计

内罗毕—马拉巴铁路穿越东非大裂谷, 线路隧道穿越许多活动断裂带。在隧道结构设计中既要考虑地震作用, 还要考虑断层的位错作用。在隧道抗震和减震设计中, 将隧道结构设计成像链条一样的结构特性, 使得隧道结构随着地震作用和断层位错, 自动调整本身的变形, 而不会导致整体性破坏。为了分析隧道结构的地震响应规律, 建立了动力分析数值模型。将人工合成100 a超越概率2%的加速度时程作为水平地震作用, 在数值模型底部输入。计算分析了地震作用下隧道结构的响应规律和隧道结构的链条特性。计算表明链条一样的隧道结构能够很好地起到抗震消能作用。另外, 由于断层的位错作用造成隧道内限界减小, 使得隧道失去正常的通行功能。因此在断层位错设计中, 根据断层特点、接触网的型式, 综合考虑制定隧道断面扩挖尺寸。当断层位错发生影响正常交通运营时, 根据正断层的特点, 扩挖下盘隧道, 回填上盘隧道。调整线路坡度和接触网的绝缘距离、悬挂方式来消除断层的位错量, 从而实现隧道内线路正常通行条件, 而不用改建隧道二衬结构。     

公路长隧道通风排气孔构想与施工技术方法的探讨

针对现有公路长隧道通风排气不良的状况,结合国内先进的科技成果和技术能力,提出一种新式、经济的通风排气孔的构想,探讨公路长隧道通风排气孔施工技术的可行性。认为该通风排气孔构想不仅在交通工程,而且在矿山巷道、国防洞库等具有广泛的应用前景。     

基坑开挖对近邻运营地铁隧道影响规律研究

对某邻近基坑开挖的地铁隧道的水平位移和沉降的时空分布做了深入分析。由于软土的蠕变效应,应考虑基坑分块开挖的先后顺序造成的时空效应的影响,以及基坑围护体系的水平支撑结构对土体位移的限制作用。基坑开挖对邻近地铁隧道的影响范围为2.5倍开挖深度,而对于远基坑的右线,影响范围更低,甚至低至1.5倍开挖深度。将基坑和隧道的监测数据联系分析,得到比值与水平距离的关系曲线,将基坑监测数据代入拟合公式,对地铁水平和垂直位移进行估算。隧道水平位移与邻近的同深度土体水平位移的比值（?）,其最大累计位移点的? 较多地处在0.60～0.65范围,在底板浇筑都已完成后,稳定在0.60。隧道沉降与邻近地表沉降的比值（?）,其最大累计沉降点的?,较多地处在0.50～0.60间,底板浇筑完成后,稳定在0.52±0.05水平。     

突水矿井动水巷道骨料灌注截流可视化平台研制与试验研究

通过骨料灌注法进行动水巷道截流堵水是矿井淹没后进行救援和复矿的重要方法。为研究骨料灌注截流堵水机理,基于水头高度、流速、巷道尺寸、倾角、糙度、骨料粒径、灌注速度等因素建立大型骨料灌注截流试验平台,并依托平台进行单孔、多孔灌注试验,分析动水巷道骨料运移堆积规律。结果表明:骨料正常灌注期间堆积体具有向下游运移生长的特性,迎水面和背水面由涡流控制的坡脚形态存在差异化现象;低流速条件下骨料会快速接顶且孔间存在空腔,高流速条件下孔间堆积体逐渐接龙、灌注量在下游相互叠加;残余过水通道沿截面呈U形分布,存在扰流接顶效应、空气掏蚀效应、堵孔效应、溃坝冲刷效应等典型动力学现象;结合解析法和数值法,对骨料颗粒的起动速度及典型现象进行计算和模拟,验证了试验平台的可靠性;通过浆液灌注实验验证浆液配比和骨料粒径对注浆效果存在重要影响,浆液在骨料堆积体中存在“上多下少”的空间分带性。试验平台的研制对截流堵水工程技术优化具有指导意义。      

西安地铁隧道穿越地裂缝带的计算模型探讨

通过对西安地铁隧道穿越地裂缝带的大型物理模型试验成果的分析,提出在地裂缝活动时,穿越地裂缝带的地铁隧道有以下两个方面的变化特征：一是作用于隧道的荷载发生改变;二是在隧道底部产生脱空现象。这种脱空现象无论在整体式隧道还是盾构隧道中都会出现。造成隧道在界面上与土体脱空的原因是隧道和周围地层的变形不协调。脱空区域的大小对地铁隧道的变形与内力计算会产生明显影响。在对隧道变形特征分析的基础上,总结得出了西安地铁穿越地裂缝带隧道变形的4种计算模型：对于整体式长隧道,可以采用一端固定而另一端简支,或一端固定而另一端定向支承的计算模型;对于整体式短隧道,可以采用外伸梁模型;对于盾构隧道,可以采用一端固定而另一端定向支承的计算模型。最后,对脱空条件下隧道数值分析的建模问题进行了讨论。算例分析表明：在数值计算中,对于隧道与土体接触面的界面处理非常关键,否则将造成计算结果的重大误差。     

盾构隧道注浆对既有隧道影响的离心模拟研究

随着地铁网络不断完善,越来越多的新建盾构隧道近距离穿越既有隧道,然而对于盾构隧道近距离穿越既有隧道影响的研究尚不够完善。以上海典型软弱地层为背景,通过离心模型试验,研究了不同注浆率下的盾构上穿越施工对既有隧道以及周围地层的影响。选用排液法在离心场中模拟盾构施工,在不停机状态下成功模拟隧道开挖卸载、地层损失和注浆效应。分析了在不同的注浆率条件下,既有隧道在上穿越施工期和工后长期的位移、周围孔压和纵向应力的变化规律。试验结果表明,新建隧道近距离上穿越既有隧道时,隧道开挖的卸载效应等会导致既有隧道的隆起,但随着注浆率增大,既有隧道的隆起量减小。但过高注浆率对周围土体扰动较大,从而导致工后既有隧道的沉降也越大。     

Numerical Simulation of Explosion in Twin Tunnel System

Rapid growth of urban population in Indian cities have led traffic congestion leading to demand for scientific utilization of underground space. Immediate underground level and deep level underground below the major arterial roads are the sustainable spaces available for meeting the demand of the future traffic/transport. Due to recent increased transit activities it has become one of the soft targets by terrorists or prone to catastrophic accidents in recent years which have increased the importance of rock structures study under explosive loading. In this paper, the response of a underground metro tunnel subjected dynamic loads have been investigated including explosive capacity (30 kg TNT), ground characteristics, liner thickness and blast pressure characteristics. Blast pressure representing CONWEP air blast loading model with positive over pressure phase was applied to lining of tunnel. A three dimensional explicit finite element method was used to analyze dynamic response and damage in twin tunnels of underground metro. It is found that liner of thickness 28 cm will start deforming at the explosive loading of more than 65 kg TNT.     

陕南特长公路隧道水压致裂法地应力测量结果及工程地质意义分析

中国西部地区地势复杂,区域构造应力场各向异性显著,了解地区地壳应力状态是判断隧道设计阶段线路布设合理性的基础,也是预测隧道施工过程可能出现岩爆、断层滑动等其他工程灾害的重要参数。为了研究陕南特长高速公路隧道现今地应力状态,基于古仙洞隧道钻孔(ZK10钻孔)与化龙山隧道钻孔(ZK11钻孔)水压致裂地应力测量,获得了两隧道现今地应力分布特征。古仙洞和化龙山特长深埋隧道最大埋深处S_H值分别为13 MPa和22 MPa;古仙洞与化龙山隧道的应力关系分别为S_H>S_h>S_v和S_H>S_v>S_h,水平主应力起主导作用;S_H方向为近北西—北西西向,与区域现今构造活动背景基本一致,主要受秦岭造山带活动断裂影响。基于地应力测量结果、相关理论及判断依据认为:最大水平主应力方向与洞轴线夹角,有利于隧道围岩稳定,研究区内古仙洞与化龙山隧道的总体布置是合理的;采用岩石强度应力比法、陶振宇判据、Russenes判据和岩石应力强度比法综合判定研究区内两隧道不具备发生中等强度以上等级岩爆的可能;利用莫尔-库伦准则及拜尔定律,摩擦系数μ取0.6~1.0,对研究区内两隧道的现今地应力状态分析后发现,两隧道附近断裂带的地应力大小未达到地壳浅部断层产生滑动失稳的临界条件,处于较稳定的应力状态。      

川藏交通廊道雅林段水文地质结构控制的水热循环及隧道热害特征

川西藏东地区水热体系空间分布与川藏交通廊道布局关系的特殊性,使得隧道难以回避复杂多样的水热灾害.为系统分析工程面临的热害问题,对控制水热循环的水文地质结构进行辨识,辅以地球化学特征、钻孔温深关系解析,分析隧道穿越地热系统时可能遭遇热害的类型及灾变特征.活动性深大断裂与大型褶皱为区内重要控热构造,结合次级断裂、岩石富水性、热水出露特征,梳理出7类控制水热循环的水文地质结构;结合隧道与上述结构的空间关系、水热特征影响要素归纳出两大类、13小类的热害类型.典型案例分析显示康定1#隧道出口段、拉月隧道中段分别穿越折多塘温泉、拉月温泉水热系统排泄区,两段可能遭遇高温高压、突发性涌突水灾害.      

采用矿山法构筑区间盾构隧道渡线段的方案探讨

针对北京地区地质条件,提出了在区间盾构隧道之间采用矿山法构筑渡线隧道的方案,即先在最大开挖断面处拆除管片,沿横向扩挖出一条施工通道;然后在施工横通道侧壁开口,从大断面向小断面进行渡线隧道的断面渐变段、双联拱段和分离单洞的施工,从而在两条区间盾构隧道之间采用矿山法完成渡线隧道的施工;最后,应用FLAC数值计算软件,探讨了管片拆除及隧道断面扩挖引起的地表沉降和塑性区分布范围。研究结果表明,针对北京地区的地质条件,提出的在区间盾构隧道之间采用矿山法构筑渡线隧道的方案具有工程适用性。     

偏压、错台小间距隧道施工位移场动态模拟分析

采用三维非线性有限元法,对偏压、错台的浅埋小间距隧道在不同开挖顺序下的动态施工过程进行了模拟。通过对位移场的分析,研究了其施工力学特性。由于两隧洞之间的相互影响,并行小间距隧道对围岩的扰动程度大于两独立隧道作用的叠加;相互影响对中间岩柱的作用最为明显,对洞周、地表影响相对较弱。两洞开挖顺序不同,最终位移场的分布规律相同,但量值上存在一定差异。研究给出了在偏压、错台情况下的两洞开挖的合理顺序。     

静压沉桩引起邻近隧道水平位移计算方法研究

静压沉桩过程中会产生强烈的挤土效应,使得桩周土及邻近的地下电缆隧道产生扰动变形,如果变形过大,可能破坏隧道的防水结构,造成隧道渗漏水,严重影响隧道的正常使用及安全。在圆柱孔扩张理论及基床系数法的基础上,研究了饱和软土地区静压沉桩作用下周边地层及邻近既有电缆隧道应力及水平位移的理论计算方法;考虑群桩效应,推导了单排群桩施工造成邻近既有电缆隧道水平位移的理论计算方法,并研究了群桩效应影响系数的取值范围;最后,开展了实际工程的理论计算和数值模拟。研究结果表明：提出的方法可方便计算出单桩及单排群桩施工造成的邻近既有电缆隧道的水平位移,计算结果与数值模拟结果吻合性良好。研究可为有邻近桩基施工时电缆隧道的扰动预测及保护提供参考。     

小间距隧道施工性态监测与稳定性分析

在分岔隧道施工过程中,小间距段支护体系力学性态直接反映分岔隧道的稳定状况,结合沪－蓉线庙垭分岔隧道,对小间距中墙薄弱处侧向加固进行了理论分析,通过对围岩变形和围岩压力、钢支撑内力、锚杆轴力等支护体系监测成果的系统分析,以及中墙爆破振动现场试验研究,评判了小间距隧道的稳定状况,所得结论可为日后同类工程的设计、施工、监测提供有益的借鉴。     

Car owner attitudes to mass transit use: A Nigerian pilot study

The problem of traffic congestion is growing in intensity in Nigeria's urban centres. The remedy that has so often been prescribed is the introduction of mass transit modes of transportation in the cities. This suggestion presumes that when provided, private car owners will use the mass transit modes. This pilot study explores the likelihood of car owners using mass transit if provided. It finds that over half of the car owners would still stick to the use of their cars even when the best conditions of transit exist. It is contended, however, that the proportion of car owners willing to use mass transit would increase when good and well-organized mass transit modes are established. This would be more so as the inconveniences and hardships of traffic congestion become increasingly felt by the private car driver. Public policy priority in this regard should therefore be directed in the first instance towards the provision of a decent and efficiently operated municipal transit services.     

叠落盾构隧道受力分析及管片配筋

在现代城市轨道交通建设中,上下叠落地铁盾构隧道越来越多,这类叠落盾构隧道相互影响,塌落拱多次叠加,传统解析法计算隧道围岩压力存在困难,目前缺乏相应的叠落隧道围岩应力计算方法。为了研究叠落盾构隧道受力分析及管片配筋,以北京地铁6号线南锣鼓巷站—东四站叠落盾构隧道为工程实例,根据弹塑性理论模拟隧道开挖过程计算塌落拱多次叠加,结合强度折减法计算叠落隧道塑性区,然后根据塑性区计算塌落拱高度和围岩压力;根据厚壁圆筒理论,计算盾构施工和列车运营对下方隧道附加应力;根据以上分析,计算叠落隧道的下方盾构隧道管片内力并配筋。