Automatic Road Tunnel Crack Inspection Based on Crack Area Sensing and Multiscale Semantic Segmentation

The detection of crack defects on the walls of road tunnels is a crucial step in the process of ensuring travel safetyand performing routine tunnel maintenance. The automatic and accurate detection of cracks on the surface of roadtunnels is the key to improving the maintenance efficiency of road tunnels. Machine vision technology combinedwith a deep neural network model is an effective means to realize the localization and identification of crackdefects on the surface of road tunnels.We propose a complete set of automatic inspection methods for identifyingcracks on the walls of road tunnels as a solution to the problem of difficulty in identifying cracks during manualmaintenance. First, a set of equipment applied to the real-time acquisition of high-definition images of walls inroad tunnels is designed. Images of walls in road tunnels are acquired based on the designed equipment, whereimages containing crack defects are manually identified and selected. Subsequently, the training and validationsets used to construct the crack inspection model are obtained based on the acquired images, whereas the regionscontaining cracks and the pixels of the cracks are finely labeled. After that, a crack area sensing module is designedbased on the proposed you only look once version 7 model combined with coordinate attention mechanism (CAYOLOV7) network to locate the crack regions in the road tunnel surface images. Only subimages containingcracks are acquired and sent to the multiscale semantic segmentation module for extraction of the pixels to whichthe cracks belong based on the DeepLab V3+ network. The precision and recall of the crack region localizationon the surface of a road tunnel based on our proposed method are 82.4% and 93.8%, respectively. Moreover, themean intersection over union (MIoU) and pixel accuracy (PA) values for achieving pixel-level detection accuracyare 76.84% and 78.29%, respectively. The experimental results on the dataset show that our proposed two-stagedetection method outperforms other state-of-the-art models in crack region localization and detection. Based onour proposedmethod, the images captured on the surface of a road tunnel can complete crack detection at a speed often frames/second, and the detection accuracy can reach 0.25 mm, which meets the requirements for maintenanceof an actual project. The designed CA-YOLO V7 network enables precise localization of the area to which a crackbelongs in images acquired under different environmental and lighting conditions in road tunnels. The improvedDeepLab V3+ network based on lightweighting is able to extract crack morphology in a given region more quicklywhile maintaining segmentation accuracy. The established model combines defect localization and segmentationmodels for the first time, realizing pixel-level defect localization and extraction on the surface of road tunnelsin complex environments, and is capable of determining the actual size of cracks based on the physical coordinatesystemafter camera calibration. The trainedmodelhas highaccuracy andcanbe extendedandapplied to embeddedcomputing devices for the assessment and repair of damaged areas in different types of road tunnels.

Resilience analysis of road tunnels subject to refurbishment work

After some tragic fire events,Directive 2004/54/EC was issued to ensure a minimum safety level for tunnels belonging to the Trans-European Road Network longer than 500 m.Nowadays,most of the Italian road tunnels are still not in compliance with the minimum safety requirements,thus refurbishment works are often planned.By developing a traffic macro-simulation model,this paper aims at assessing the resilience of an existing twin-tube motorway tunnel when one of its tubes is partially or completely closed due to planned activities.Several scenarios were investigated,also considering the availability or not of an alternative itinerary in the surrounding transportation network.The average vehicles’speed was used as a functionality parameter,while the resilience metrics were the resilience loss,the recovery speed,and the resilience index.The findings showed higher resilience losses for complete closure rather than partial closure of the tube under planned refurbishment works.The implementation of digital technologies,such as variable message signs,might reduce the resilience loss of the tunnel system.This research might represent a reference for tunnel management agencies in the choice of the most appropriate traffic control strategy to improve tunnel resilience in the event of planned activities.

Determination of critical parameters in the analysis of road tunnel fires

The analysis of the fluid characteristics downstream of a fire source in transportation tunnels is one the most important factor in the emergency response, evacuation, and the rescue service studies. Some crucial parameters can affect the fluid characteristics downstream of the fire. This research develops a statistical analysis on the computational fluid dynamics(CFD) data of the road tunnel fire simulations in order to quantify the significance of tunnel dimensions, inlet air velocity, heat release rate, and the physical fire size(fire perimeter) on the fluid characteristics downstream of the fire source. The selected characteristics of the fluid(response variables) were the average temperature, the average density, the average viscosity, and the average velocity. The prediction of the designed statistical models was assessed; then the significant parameters' effects and the parameters interactive effects on different response variables were determined individually. Next, the effect of computational domain length on the selection of the significant parameters downstream of the fire source was analyzed. In this statistical analysis, the linear models were found to provide the statistically good prediction. The effect of the fire perimeter and the parameters interactive effects on the selected response variables downstream of the fire, were found to be insignificant.

Monitoring in Building Road Tunnel Across Coal Measures

In some cases coal measures,goaf,big caves,and huge faults,as well as high initial stress cannot be avoided in road tunnel excavation.These geological features may make it more difficul practical tunnel construction. So it is necessary to take strong precautious measures against gas outburst,water bursting and roof fall in a tunnel across coal measures with risk of gas outburst.The techniques,such as advance drilling exploration,multiple-cycle shallow depth hole controlled blasting,reinforced supporting,which include concrete grouting and twice supporting,and monitoring measures are often applied in the construction of tunnels and satisfied results are achieved. Results in this paper can help others to get experiences in road tunnel construction with similar geological features.

Applications of airtight concrete grouting to road tunnels

Road tunnel excavation often traverses coal strata, which is at risk of firedamp explosion that usually results in disaster. Airtight concrete grouting is popularly used in this kind of tunnel project. Based on the essential theory of mechanics of fluids in porous media, the principle of improving concrete airtight property and its influential factors are investigated. The proportioning tests and monitoring method for airtight concrete are introduced, which is illustrated by a case study applied to the project of the Huayinshan Tunnel. It is proved by engineering practices that the achievement of this research work is beneficial to tunneling project across coal strata.

An air cleaner for road tunnels

an air cleaner employing pulse induced plasma chemical process to remove dust and carbon monoxide (CO) in road tunnels is presented, which is composed of mainly a precipitator, a reactor, a flow control system, a power supply and a measurement system. Its performances are studied in simulated air conditions. It is found that the rate of dust removal is dependent on the voltage of the pulse power, the distance between the two dust collecting plates of the electrostatic precipitator, the effective length of the precipitator and the air flow rate in the precipitator, and that of CO removal is affected by the voltage and frequency of the super pulse power, the air flow rate in the reactor and the relative humidity of air. Applying such an cleaner of a proper design to the treatment of polluted air at a flow rate of 7 m/s can achieve the rate of dust removal up to 93 % and that of CO removal up to 72.6 %, which efficiently controls the concentrations of CO and dust under allowable limits. It is implied that the proposed air cleaner is a potential solution to air control in road tunnels, and is prominent for its performances and saving the huge cost of longitudinal ventilation tunnel or vertical vent and ventilation facilities.

Connection of the prefabricated updeck of road tunnels by a short lap-spliced joint using ultra-high-performance fiber-reinforced concrete

Prefabricated internal structures of road tunnels,consisting of precast elements and the connections between them,provide advantages in terms of quality control and manufacturing costs.However,the limited construction space in tunnels creates challenges for on-site assembly.To identify feasible connecting joints,flexural tests of precast straight beams connected by welding-spliced or lap-spliced reinforcements embedded in normal concrete or ultra-high-performance fiber-reinforced concrete(UHPFRC)are first performed and analyzed.With an improvement in the strength grade of the closure concrete for the lap-spliced joint,the failure of the beam transforms from a brittle splitting mode to a ductile flexural mode.The beam connected by UHPFRC100 with short lap-spliced reinforcements can achieve almost equivalent mechanical performance in terms of the bearing capacity,ductility,and stiffness as the beam connected by normal concrete with welding-spliced reinforcements.This favorable solution is then applied to the connection of neighboring updeck slabs resting on columns in a double-deck tunnel.The applicability is validated by flexural tests of T-shaped joints,which,fail in a ductile fashion dominated by the ultimate bearing capacity of the precast elements,similar to the corresponding straight beam.The utilization of UHPFRC significantly reduces the required lap-splice length of reinforcements owing to its strong bonding strength.

THE TRANSIENT AERODYNAMIC CHARACTERISTICS AROUND VANS RUNNING INTO A ROAD TUNNEL

In this article,the processes of vans running into a one-way two-lane road tunnel are simulated numerically using the dynamic mesh technique and RNG k ？ ε turbulence model.The transient aerodynamic characteristics around vans are obtained in three cases：a single van,two vans side-by-side and two vans one after another running into the tunnel,respectively.Through a comparison with the results of the wind tunnel experiment,the transient simulation method is verified.The results show that,when a van runs into the tunnel,the aerodynamic drag coefficient increases near the tunnel entrance,and after entering the tunnel,the side force is generated,pointing to the tunnel wall nearer to the van.When two vans run into the tunnel side-by-side,their drag coefficients increase by 50%,and the side force varies sharply with directions changing twice near the tunnel entrance.When two vans run into tunnel one after another,the aerodynamic characteristics around the van in the front is similar to that of a single van,but the aerodynamic forces on the van behind do not have obvious change.Among the three cases,the aerodynamic forces have a sharp change when two vans run side-by-side,so driving side-by-side into a tunnel should be avoided for safety.

An exploratory study on road tunnel with semi-transparent photovoltaic canopy-From energy saving and fire safety perspectives

Road tunnels consume a large amount of energy,especially in the Canadian cold climate,where the roads are heated electrically or deicing during the winter.For a more sustainable and resilient road tunnel energy system,we conducted an exploratory study on installing a semi-transparent photovoltaic(STPV)canopy at the entrances and exits of a tunnel under a river.The proposed system generates solar-powered electricity,improves thermal and visual conditions,and reduces energy loads.In this study,field measurements of road surface temperature and air temperature were conducted,and numerical simulations with and without STPV were performed to study air and road surface temperatures under different traffic speeds.The field measurements show the road surface temperatures are higher than the air temperature on average.The interior air and road surface temperature were measured to be above 0°C,even though the outdoor temperature is far below 0°C,thus significantly reducing the need for deicing in winter using salts.The simulations show that the air and surface temperatures elevate due to the solar transmission heat through the STPV canopy,thus reducing deicing energy consumption significantly.The fire safety analysis also showed that the proposed system's top opening should be located near the tunnel entrance instead of the canopy entrance for better smoke exhaust during a fire.

Supporting decision-making processes for selecting fire safety measures for road tunnels

Selecting fires safety measures for road tunnels relies mainly on strict regulatory requirements. However, the choice should also be based on many different criteria and ranking of alternatives should take place. Existing methods exhibit lack in dealing rigorously with measures’ selection amongst different alternatives. This paper contributes to the body of knowledge by proposing a novel method, named EVADE, which aims to incorporate diverse stakeholders’ views and provide a meaningful ranking of alternatives.To do so, it estimates the tunnel level of safety taking into account only any standard measures existing. Subsequently, the performance of additional measures is examined.Then, a list of the most significant criteria that are valuable to judge the appropriateness of selected measures is introduced. The relative importance amongst the decision criteria is calculated through the Analytic Hierarchy Process, based on the expert opinion. Sensitivity analysis through Monte Carlo simulation is embedded to allow for a meaningful prioritization of the decision criteria. Thus, the alternatives’ ranking comes as a distribution instead of a single number, providing the decision-maker richer information for selecting the most suitable measure(s) according to the specific tunnel situation. At last, a typical tunnel is examined to showcase the utilization of the method.

Impacts of opening baffle of city road tunnels on natural ventilation performance

Based on the opening baffle mode for natural ventilation of city road tunnels,this paper studies the impacts of opening baffle on natural ventilation performance by verifying numerical simulation through model tests.By analyzing the impacts of installation angle,dimension,location,and quantity of opening baffle on ventilation performance,the paper reached the conclusions as follows:1)When installation angle is larger than 45°and tunnel ventilation is well operated,the baffle exhaust could increase by at least 30%compared to when there is no baffle.2)The baffle reaches its optimal performance when the length of the baffle is equal to the width of the city road tunnels.3)Baffle exhaust could increase by 30%when it is installed in the downstream of openings.4)The performance of a single baffle is better than that of multiple baffles.

Evaluating the role of risk assessment for road tunnel fire safety: A comparative review within the EU

Fire is the foremost critical event for road tunnels’ safety. Therefore, the European Commission introduced the Directive 2004/54/EC for enhancing tunnels’ safety since they constitute a key element of the Trans-European Road Network. The Directive has established a common ground for tunnels’ safety evaluation providing certain minimum requirements while introducing officially the use of risk assessment. Despite the signifi-cant progress, this paper illustrates that further efforts are needed. Through a comparative review of the risk assessment methods, questions about the level of harmonisation of the framework are raised. Moreover, considerable problems are highlighted, like the incorporation of the new trends emerging from the literature or the deficiencies on addressing significant issues of the analysis, such as the risk acceptance criteria and the behaviour of trapped-users. These problems can affect the risk assessment process causing both significant discrepancies and deficiencies at the estimated level of tunnels’ safety.Uncovering, thus, the deficiencies and limitations of the methods, this paper contributes to i) the discourse for initiating relevant studies to enhance tunnels’ fire safety in Europe and worldwide, and ii) the harmonisation of risk assessment methods.

公路隧道地面效应对双火源火焰合并特性影响的试验研究

为研究自然通风隧道内发生双重火灾时地面效应对双火源火焰合并特性的影响,利用1:10小尺寸隧道模型开展了一系列试验。重点探究了双火源表面与隧道地面平齐时火源间距对火焰合并概率与火焰合并点高度的影响。结果表明:火灾烟气从隧道两端开口流出,由隧道两端补充进的新鲜空气产生的风速导致火源间距更大时火焰依然会发生互相倾斜,在间距足够大时,火焰倾斜角度约为10°。引入一个无量纲量表示火焰合并概率随着火源间距、热释放速率的改变而变化的规律。另外,将本文的试验数据与前人的工作做了比较,发现地面效应对隧道纵向布置的双火源火焰合并行为具有极大的促进作用。同时给出了火焰合并点高度与隧道高度的比值与改良后无量纲热释放速率的关系式。

上覆软弱路基加固对既有地铁隧道沉降的影响规律

为研究道路施工引起下方既有地铁隧道的沉降问题,在地铁隧道上方斜穿施工道路的基础上,进行了现场隧道沉降变形实测研究,分析了道路在路基注浆加固、路床和路面结构层施工阶段中地铁隧道的沉降曲线。建立地铁隧道-土体-道路模型对道路施工的注浆加固过程及路床和路面结构层施工进行模拟,通过比较地铁隧道沉降计算结果与现场实测值,验证了该精细化模型的准确性。基于此,分析了路床和路面结构层总施工厚度、道路土体性质、隧道下卧土层、隧道衬砌强度等关键参数对地铁隧道的沉降影响规律。结果表明:地铁隧道的沉降值与施工厚度呈正相关关系;道路的存在对隧道的沉降影响越小,其弹性模量和泊松比对地铁隧道沉降几乎没有影响;卧土层的弹性模量越大,土层越不易变形,且地铁隧道沉降越小;衬砌弹性模量增大对地铁隧道沉降影响反而越小。

基准排放因子更新对隧道需风量的影响研究

为解决交通车辆持续更新导致的城市隧道内通风系统设计浪费和运营闲置,研究基准排放因子更新对隧道需风量的影响,并建立2种应对车辆更新的基准排放因子计算方法.首先,通过理论分析明确需风量计算式中随时间更新的关键参数为基准排放因子;随后,根据定量分析得到基准排放因子和纵坡-车速系数更新对需风量的影响;最后,结合国外理念和实际设计经验,提出2种考虑时间更新的基准排放因子计算方法.研究结果表明:我国道路隧道通风设计规范在制定基准排放因子时参考了世界道路协会(PIARC)通风报告,并分析得到了参考理由;与2000年相比,2021年的CO、NOx和PM基准排放限值分别降低了81.6%、76.7%和97.9%;建立了使用机动车污染物排放限值作为基准排放因子的最不利设计方法,计算出2018年各污染物基准排放因子(CO为0.0011 m^(3)/(辆·km),PM为0.4610 m^(2)/(辆·km)),相比于2014年《细则》分别降低84.3%和77.0%.建立并验证了基准排放因子计算方法,为城市道路隧道通风系统设计提供参考.

城市道路隧道晚高峰环境参数时空差异性分析

隧道内晚高峰的出现会导致交通流量的时空分布发生很大的变化,并进一步影响隧道内的环境参数及CO浓度。为了改善隧道内环境质量,研究人员于晚高峰时段对玉涵路隧道内空气温度、风速、CO浓度、CO_(2)浓度和颗粒物浓度进行了详细的现场实测。测试结果表明:节假日的交通晚高峰时长更短以及高峰车流量更低,从而引起节假日的风速、温升、CO_(2)增量较工作日平稳且状况更优;工作日洞内风速减小1.7~3.2 m/s,纵向温升为6.1~7.7℃;随着车辆行驶速度延迟时间的增大,风速、温升、CO_(2)增量延迟时间呈增大趋势,最大延迟时间可达70 min;工作日隧道通风应考虑交通高峰开始后20 min至交通高峰结束后70 min时间段的延迟时间。

支管排烟作用下双层隧道顶棚温度分布试验研究

针对下层隧道采用支管排烟模式的双层盾构隧道,通过开展缩尺寸模型试验对烟气温度分布进行系统研究,探讨火源功率、排烟口开启方案(排烟口数量和距离)和排烟量等关键因素对火灾烟气温度分布的影响。结果表明:随着排烟口距离的增加,顶棚烟气温度逐渐升高;开启距离火源最近的两个排烟口时,顶棚烟气温度最低;随着排烟量的增大,在远离火源的区域顶棚烟气温度逐渐降低;火源上下游顶棚下方温度沿隧道纵向呈现指数衰减规律,在不同的排烟量和火源功率下,相对温度衰减ΔT_(x)/ΔT_(max)的值变化不大。通过对试验数据进行拟合分析,推导出支管排烟模式下,火源上下游顶棚烟气温度纵向衰减预测模型。

带上盖开发隧道通风流场特性及射流风机偏转角度研究

带上盖开发的隧道结构复杂,通风流场紊乱,隧道运营通风能力难以得到保障。揭示这类隧道的通风流场特性,优化隧道风机布置参数具有重要意义。以广州市某珠江过江隧道工程为背景,利用数值模拟方法,探究不同风机偏转台数、偏转角度工况下隧道通风流场特性、风机升压能力。结果表明:带上盖开发隧道风机安装位置受限、复杂结构通风阻力大,导致隧道通风流场分布不均,风机升压能力较差,风机难以提供可靠的运营通风能力;带上盖开发隧道设置3台吊顶式风机时,通过合理的设置风机偏转台数和风机偏转角度,能够稳定隧道通风流场,提高平均风速,优化隧道内通风效果;当3台吊顶式风机全部偏转布置或风机偏转角度大于5°时,虽能增大未安装风机一侧的通风风速,但会导致射流分布不均,安装风机一侧风速降低,过多射流偏转也将携带更多动能撞击隧道壁面,导致射流遭受的能量损失增大,不利于隧道通风流场的稳定;采用2台吊顶式风机偏转2°~5°布置时,此时隧道内流场分布均匀,射流风机升压系数为0.7~0.8,隧道内风机射流阻力损失约28~29 Pa,可提升风机升压力,减小风机射流阻力损失,利于带上盖开发的隧道运营通风。研究结果可为优化带上盖开发隧道射流风机布置方式和保障运营通风效果提供参考。

我国城市地下空间盾构法隧道工程技术新进展

基于盾构施工特点,对盾构法施工技术的发展过程和创新进展进行调查研究,总结盾构法施工技术在地铁、市政公路、城市铁路、城市水工隧洞、城市综合管廊等工程中的最新应用,阐述城市盾构法隧道在地质条件多样化、越江跨海常态化、结构断面多元化、地面条件复杂化、隧道结构耐久性等方面面临的技术挑战。介绍超大直径盾构装备、大直径泥水盾构常压换刀、多模盾构、类矩形盾构隧道建造、联络通道机械法施工、软硬极端悬殊地层掘进、富水砂卵石地层土压平衡盾构、地下高地震烈度盾构隧道减隔震抗震和超长距离综合施工等技术创新成果;总结不良地质识别、设备状态实时感知、同步推拼连续掘进、盾构自动驾驶技术、盾构智能化管控平台等盾构智能掘进技术进展;指出城市地下空间建设盾构法隧道工程的发展趋势,地铁隧道、城市道路、综合管廊、城市给排水等设施需要不断更新,并网络化,盾构法隧道技术需要不断发展,盾构法隧道智能化施工需日趋精益。未来盾构装备将朝着“多模式、无刀化、外星化”等多元化,多源信息感知、管片智能拼装、地质探测预报、自主感知掘进决策等智能化以及特大直径、超长距离、超大埋深、超高水压等方向发展。

新建隧道爆破开挖对路基边坡稳定性影响分析

为分析隧道爆破开挖对邻近路基边坡稳定性的影响,以三峡枢纽茅坪港疏港铁路十里坪隧道并行三峡翻坝高速路基边坡工程为依托,采用理论计算和midas GTS NX数值模拟的方法,研究了隧道爆破开挖对邻近高速公路路基边坡稳定性的影响。研究结果表明,采用经验公式计算的边坡峰值振速为1.06~2.66 cm/s,数值模拟计算的边坡峰值振速为0.882 cm/s,均小于3 cm/s,并且隧道建设前后,路基边坡的安全系数均大于1.35,因此新建十里坪隧道爆破施工对于翻坝高速路基边坡的影响可控。研究成果可为类似公铁并行的涉路工程设计及安全技术评价提供参考。