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.

Discussion on Structural Health Monitoring of Urban Underground Road Tunnel

The number of urban underground road tunnels in China is increasing year by year,and health monitoring of tunnels is an effective management method to ensure their structural integrity.However,for shorter underground road tunnel projects,insufficient investment often leads to less frequent application of health monitoring systems.The application of intelligent structural health monitoring means can not only reduce the project cost but also help workers fully understand the actual situation of the tunnel structure.Therefore,this paper analyzes the characteristics,problems,and design of the urban underground road tunnel structural health monitoring system,and discusses the implementation of the urban underground road tunnel structural health monitoring system.

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.

Limiting Nuisance for Traffic during the Refurbishment of the Heinenoord Tunnel in The Netherlands:In Search of Resilience Possibilities

The Heinenoord Tunnel in The Netherlands connects the Hoeksche Waard Island with the city of Rotterdam.The tunnel is 614 m long,consists of two unidirectional tubes(3 lanes each)and has an average daily traffic load of 92,100 vehicles.The tunnel was opened for traffic in 1969.The structure is basically still sound,but a full refurbishment of the installations and systems is required,because they are end of life.A long closure of the tunnel(or even one tube)is not possible,because alternative routes are scarce and require significant extra travel time,not suitable for the high traffic load.Thus,various scenarios were considered to assure the accessibility of the Hoeksche Waard during the works,scheduled for 2023-2024.Multi-criteria analyses were performed for each scenario,taking into account the total project cost,societal cost(due to extra travel time)and the total required time span for the works.Refurbishment through“parallel assembly”proved to be optimal.This concept means that the new installations and systems are installed next to the current ones,that will remain in service until the end phase of the refurbishment.The existing installations and systems are only dismantled after integral testing has shown that the completed new ones work properly.This approach allows most of the works to be carried out during a series of night and weekend closures of just one tube.This limits nuisance,because one driving direction is always left undisturbed,while the closure for the other driving direction takes place in low-traffic periods.This paper describes the applied method to select the optimal refurbishment approach,as well as the(partly unconventional)measures that are implemented to enhance the resilience of the tunnel system to assure as much availability for traffic as possible,also during future maintenance works.

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.

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.

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.

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。

基于云模型的某近间距盾构隧道施工风险评估案例研究

相较于一般的盾构施工,近间距盾构施工中后行隧道施工不仅难度大、风险高,还会造成既有隧道的结构变形和位移,降低既有隧道的安全性,因此需要对近间距盾构施工进行风险识别和评估,为制定控制措施提供支持。依托某市轨道交通七号线三阳路过江超大直径隧道近间距盾构施工实例,根据其工程特点归纳出典型风险指标,并基于熵权法计算指标权重,采用云模型评估方法对各个风险进行评估。实际施工中结合评估等级采取针对性措施,保证了工程施工安全,同时也验证了此方法的有效性和可行性,可为类似工程风险评估提供参考。

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。

高桥隧比条件下桥隧相连的隧道洞口联络道设计探讨——以重庆巫溪至陕西镇坪高速公路为例

为确定高桥隧比条件下高速公路桥隧相连的特长隧道洞口联络道的转换长度和结构形式,采用数值模拟方法,选用18.1 m的长头铰接列车为典型车辆,针对10 m~30 m五种左右幅间距及0°~45°四种行驶转换角度,模拟车辆行驶轨迹并计算联络道通行的最小长度。结果表明:1)在满足转换车道基本长度的前提下,模拟隧道洞口联络道推荐长度采用30 m或40 m;2)基于模拟结果推荐的联络道长度,为超高桥隧比的巫镇高速隧道洞口联络道设计提供了重要的基础依据;3)在运营期间,该高速的洞口联络道实现了养护维修或异常工况下的交通转换,有效提升了道路防灾减灾和运营养护能力,为类似工程的设计提供了有益参考。

空气净化技术在超长水下公路隧道通风中的应用研究

空气净化技术是解决公路隧道机动车废气污染的一种重要手段,但目前国内相关应用案例和研究成果较少,无法指导超长水下公路隧道通风设计。本文结合国内某超长水下公路隧道案例,提出了3种可行的净化通风方案;并通过理论计算得到了不同交通工况下隧道内典型污染物沿隧道长度的浓度分布情况,分析了不同净化通风方案的污染物控制效果。通过经济性、环保性、可实施性等多方面比选,确定了适合应用在超长水下公路隧道的空气净化通风方案。

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.

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。

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。

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。

隧道坡度对烟气蔓延特性及临界风速影响研究

隧道长大纵坡产生的“烟囱效应”增加了火灾烟气控制难度。为研究隧道坡度对烟气蔓延规律的影响,采用理论分析和数值模拟相结合的方法,探明了隧道坡度对烟气蔓延特性的影响,建立了适用于有坡隧道的临界风速计算模型。结果表明:1)火源上游烟气长度减小的变化率大于火源下游烟气长度增长的变化率;2)拱顶较高一侧烟气的稳定流速与隧道坡度呈二次方增长关系;3)无坡度隧道与单面坡隧道内最高温度升温曲线变化趋势不同,隧道无坡度时,温度先迅速升高后趋于一条直线,当隧道存在坡度时,温度随时间变化先升高后降低,最后逐渐趋于平稳;4)距离火源30 m左右为隧道内横断面上可视度分布规律变化的临界距离,坡度越大,人眼特征高度2 m处最低可视度越高;5)提出了坡度隧道临界风速修正系数,建立了适用于有坡隧道的临界风速计算模型,给出了不同火灾规模的烟气控制措施。

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。

中东欧国家与中国公路隧道防火理念对比研究——以黑山南北高速公路项目为例

为指导中国企业在中东欧国家进一步开展公路隧道建设,以中国企业在欧洲建设的最大公路基建项目黑山南北高速公路为例,进行公路隧道防火理念对比研究。黑山南北高速公路具备各类长度隧道16座,全过程基本采用欧洲标准建造,由欧洲公司进行监理,所选设备基本都在欧洲当地生产,因此其隧道防火理念可反映中东欧国家乃至整个欧洲地区的技术水平和建设理念,具备典型代表意义。采用比较分析法对隧道火灾风险评估报告、防火主设计、实施情况等进行分析研究,其中隧道火灾风险评估报告由具备欧盟认可的防火资质且独立于公路建设业主的第三方进行评估。评估主要针对与火灾安全相关的隧道设施配置规模,评估结论需提交给业主,并要求设计单位严格依据评估结果开展设计。同时也对中东欧国家和中国在公路隧道火灾安全风险评估、疏散逃生、消防救援、防火安全设计等理念上的差异进行综合对比。结果表明:中东欧国家公路隧道关于整体防火、防火分区、消防救援等防火理念相比中国更具有安全性、智能性,因此可为中国隧道防火安全建设提供一定借鉴,同时也可用于指导中国企业在中东欧乃至整个欧洲开展公路隧道建设。