Drivers'fixation transfer characteristics in urban tunnels

To improve the safety performance of urban tunnels,the fixation transfer characteristics of drivers with different driving experience levels in urban tunnels were investigated.First,a real vehicle test was performed in an urban tunnel,and the eye movement data of 10 drivers with different driving experience levels were collected using a Dikablis eye-tracking system.Second,the driver fixation range was divided into eight areas of visual interest by using the K-means clustering method,and the fixations in different sections of the tunnel were comparatively analyzed.Finally,on the basis of the divided areas of visual interest,fixation transfer rules and the stationary distribution characteristics of drivers with different driving experience levels on different sections of the tunnel were discussed using Markov theory.Results indicate that drivers'probability of repeated fixation is greater and that the efficiency of visual search is lower at internal sections of tunnels than in external sections.Drivers obtain information mainly from the straight upper front and straight lower front areas,and the probabilities of fixation points in these two areas at the threshold and exit sections are significantly higher than those in other sections.Relative to experienced drivers,novice drivers allocate little attention to the straight upper front area and rear-view mirrors.Hence,they have weak fixation when looking forward,and they lack experience in obtaining information on rear-approaching vehicles and controlling speed.

Research on Deformation Control Indicators and Standard of Urban Traffic Tunnel Construction Adjacent to High-rise Building

The biggest environmental problem caused by the construction of tunnels adjacent to high-rise buildings is the settlement of buildings.The paper analyzes the influence of tunnel excavation on the deformation of the superstructure and the deformation mode of the superstructure.It introduces the indicators and standards for the construction control of tunnel adjacent to the building at home and abroad.Combined with the Yuzhong tunnel project under construction in Chongqing,the main monitoring indicators and control standards of the Yuzhong Tunnel passing through the main buildings are given after comprehensive analysis and considerations,which provide a reference for the deformation control indicators of similar urban traffic tunnels adjacent to high-rise buildings.

Effect of pipe characteristics in umbrella arch method on controlling tunneling-induced settlements in soft grounds

Recent developments in tunneling have stimulated design practitioners to more effectively utilize the underground spaces.However,tunneling at shallow depth in soft grounds gives rise to concerns associated with tunnel instability.Umbrella arch method(UAM),as a pre-reinforcement approach of tunnels in complex geological conditions,is widely used to maintain the tunnel stability.Quantitative assessment of the impacts of the entire approach and forepoling pipe features on tunnel stability remains challenging due to the complex nature of the UAM application.This study aimed to assess the effect of pipe design parameters on reinforcing the tunnels excavated in soft grounds.This practical investigation considered the actual field conditions attributed to the tunneling procedure and UAM deployment.Then,the tunneling process was modeled and the tunnel excavation-induced settlements were calculated.The post-processed results confirmed that deploying the UAM substantially reduced the tunnel crown and ground surface settlements by 76%and 42%,respectively.Investigation of various design parameters of pipes underscored the significance of incorporating the optimum value for each individual parameter into design schemes to more effectively control the settlements.Additionally,contrasting the settlement reduction rates(SRRs)for pipe design variables showed that the tunnel stability is more sensitive to the changes in the values of diameter and length,compared to values of the installation angle and center-tocenter distance of the pipes.

A practical approach for seismic risk assessment of underground structures:A case study of Iranian subway tunnels

Active geological and young faulted zones have made Iran's territory one of the most seismological active areas in the world according to recent historical earthquakes.Some of the deadliest earthquakes such as Gilan 1990 and Kermanshah 2018 caused tens of thousands fatalities.If such violent earthquakes affect strategical structures of a country,indirect losses would be more concerning than direct losses.Nowadays there is no doubt about the vital role of tunnels and underground structures in urban areas.These facilities serve as nonstop functional structures for human transportation,water and sewage systems and underground pedestrian ways.Any external hazard subjected to underground spaces,such as earthquake could directly affect passenger's lives and significantly decrease whole system reliability of public transportation.Commonly two earthquake levels of intensities,Maximum Design Earthquake(MDE)and Operating Design Earthquake(ODE)were used in seismic design of underground structures.However,uncertain nature of earthquakes in terms of frequency content,duration of strong ground motion,and level of intensity indicate that only the two levels of earthquake(ODE and MDE)cannot cover the all range of possible seismic responses of structures during a probable earthquake.It is important to evaluate the behavior of tunnel under a wide range of earthquake intensities.For this purpose,a practical risk-based approach which is obtained using the total probability rule was used.This study illustrates a framework for evaluation seismic stability of tunnels.Urban railway tunnels of Tehran,Shiraz,Ahwaz,Mashhad,Isfahan and Tabriz were considered as study cases.Nominal value of seismic risk for three main damage states,including minor,moderate and major were calculated.

Simulation Analysis of CO Concentration Distribution in Beijing Yuntong Tunnel

In this paper, the concentration distribution of CO emitted by motor vehicles in Beijing Yuntong Tunnel is simulated and analyzed based on Fluent numerical simulation software. Firstly, the physical model of tunnel geometry is established. Secondly, the suitable control equations and boundary conditions are selected to describe the diffusion distribution of pollutants in the tunnel. At the same time, the reliability of the model is verified according to the measured data, and the distribution law of CO concentration in the tunnel is observed through the simulation results. The tunnel is unorganized at the entrance of the tunnel. In the simulation results, the CO concentration at the entrance of the tunnel is far more than the CO unorganized emission limit in Beijing. The CO emission of the tunnel should be purified to prevent pollution of the urban environment.

新建隧道正交下穿既有城市道路稳定性研究

为了评估新建隧道正交下穿既有城市道路的稳定性,本文通过分析货车车辆荷载作用下不同覆土厚度对隧道安全系数的影响,探讨了隧道与既有道路之间的相互影响机制。研究表明,当覆土厚度较浅时,隧道安全系数保持在安全水平以上,并随覆土厚度增加而上升,至5.72 m时达到峰值。随后,随覆土厚度进一步增加,安全系数虽有所下降但幅度较小。这表明隧道在正交下穿城市道路时具有良好的稳定性,但在浅覆土条件下与既有道路相互作用较为强烈。研究为隧道设计与施工提供了重要参考。

富水软土地区盾构近距离下穿地铁运营隧道的施工保护措施

[目的]富水软土地区盾构近距离下穿地铁运营隧道施工导致既有隧道结构变形控制困难,有必要对盾构下穿地铁运营隧道的施工保护措施进行研究。[方法]以南京地铁5号线盾构近距离下穿既有南京地铁1号线区间工程为例,运用MIDAS/GTS NX有限元软件对盾构近距离下穿施工进行了有限元模拟,提出了既有隧道主动保护措施,以及新建隧道盾构掘进控制措施。采用施工监测的方法,对盾构下穿期间既有隧道竖直方向位移和水平方向收敛进行监测。[结果及结论]具体施工保护措施包括:在盾构下穿施工前,对既有隧道受影响区段进行加固,通过微扰动注浆、永久性环向支撑和纵向拉紧条等措施有效降低了隧道变形,并使之符合变形控制标准;在盾构下穿施工中,基于既有隧道沉降量实时调整土压力和出土量,采取同步注浆、上下孔注浆量分配等方法进一步控制隧道变形。在盾构下穿施工完成后,针对地层的后期沉降问题,在盾构下穿段隧道内准备充足的补压浆材料和设备,根据沉降监测情况进行后续补压浆加固。上述措施能够有效减小盾构下穿施工对既有隧道的影响。

Tunnelling performance prediction of cantilever boring machine in sedimentary hard-rock tunnel using deep belief network

Evaluating the adaptability of cantilever boring machine(CBM) through in-depth excavation and analysis of tunnel excavation data and rock mass parameters is the premise of mechanical design and efficient excavation in the field of underground space engineering.This paper presented a case study of tunnelling performance prediction method of CBM in sedimentary hard-rock tunnel of Karst landform type by using tunneling data and surrounding rock parameters.The uniaxial compressive strength(UCS),rock integrity factor(Kv),basic quality index([BQ]),rock quality index RQD,brazilian tensile strength(BTS) and brittleness index(BI) were introduced to construct a performance prediction database based on the hard-rock tunnel of Guiyang Metro Line 1 and Line 3,and then established the performance prediction model of cantilever boring machine.Then the deep belief network(DBN) was introduced into the performance prediction model,and the reliability of performance prediction model was verified by combining with engineering data.The study showed that the influence degree of surrounding rock parameters on the tunneling performance of the cantilever boring machine is UCS > [BQ] > BTS >RQD > Kv > BI.The performance prediction model shows that the instantaneous cutting rate(ICR) has a good correlation with the surrounding rock parameters,and the predicting model accuracy is related to the reliability of construction data.The prediction of limestone and dolomite sections of Line 3 based on the DBN performance prediction model shows that the measured ICR and predicted ICR is consistent and the built performance prediction model is reliable.The research results have theoretical reference significance for the applicability analysis and mechanical selection of cantilever boring machine for hard rock tunnel.

Evaluation of a Micro-scale Wind Model's Performance over Realistic Building Clusters Using Wind Tunnel Experiments

The simulation performance over complex building clusters of a wind simulation model（Wind Information Field Fast Analysis model, WIFFA） in a micro-scale air pollutant dispersion model system（Urban Microscale Air Pollution dispersion Simulation model, UMAPS） is evaluated using various wind tunnel experimental data including the CEDVAL（Compilation of Experimental Data for Validation of Micro-Scale Dispersion Models） wind tunnel experiment data and the NJU-FZ experiment data（Nanjing University-Fang Zhuang neighborhood wind tunnel experiment data）. The results show that the wind model can reproduce the vortexes triggered by urban buildings well, and the flow patterns in urban street canyons and building clusters can also be represented. Due to the complex shapes of buildings and their distributions, the simulation deviations/discrepancies from the measurements are usually caused by the simplification of the building shapes and the determination of the key zone sizes. The computational efficiencies of different cases are also discussed in this paper. The model has a high computational efficiency compared to traditional numerical models that solve the Navier–Stokes equations, and can produce very high-resolution（1–5 m） wind fields of a complex neighborhood scale urban building canopy（～ 1 km ×1km） in less than 3 min when run on a personal computer.

New Model for Environmental Impact Assessment of Tunneling Projects

Designers of infrastructure are aware that the government, owners and users become more and more concerned about negative environmental impacts of tunnels, so environmental assessment of tunnels are becoming an issue in the process of tunnel design. In this study, to assess tunnels in construction and operation phases, the matrix method, through which the “Impacting Factors” and “Environmental Components” are determined, is also outlined. The affected environment was divided into thirteen components, such as Ecology, Surface water, Air quality, etc. In this paper, matrix method was applied to evaluate the impact of tunneling in three typical tunnels and compare them with standard diagrams of Environmental Components that were derived and introduced. These tunnels were: Urban Utility tunnel in Tehran, Eurasia tunnel in Istanbul and Tsuen Wan drainage tunnel in Hong Kong. Based on the acquired results, the present paper finally concluded that among three cases, Tsuen Wan drainage tunnel affects the environment in construction phase more than others, while Eurasia tunnel effects on air quality are more significant in operation phase.

高铁路基近距离上跨既有市域铁路隧道结构安全影响分析

路基近距离上跨施工对下方既有隧道结构极为不利,路基挖方会引起下方隧道上浮,路基填方将增加既有隧道结构荷载,严重影响结构安全。依托新建成渝中线路基近距离上跨既有市域铁路璧铜线云雾山隧道工程,借助有限元MIDAS构建隧址区三维数值模型,用于还原路基上跨既有隧道施工现场,通过分析隧道变形及结构受力来判定铁路路基建设运营后既有结构安全性。研究结果表明,路基建设前后既有隧道结构受力规律未发生明显改变,但由于附加上方填土荷载及列车荷载,下方隧道结构应力增加,结构最大受拉为0.54 MPa,最大受压为3.69 MPa,同时,路基填方导致下方隧道结构整体沉降,相较而言,隧道拱顶处受影响程度更大,拱顶最终沉降变形为4.672 mm,现场监测验证了数值计算的合理性。荷载结构法计算表明,路基修建前后下方既有隧道结构最小安全系数分别为6.22、4.50,路基修建对下卧隧道有一定影响,但仍在安全可控范围内。

Air quality nearby road traffic tunnel portals: BTEX monitoring

A monitoring campaign of BTEX （benzene, toluene, ethylbenzene, o- m- and p-xylene） was carried out nearby two tunnel portals in the urban area of Naples with the aim to verify air quality in this kind of urban sites. Sampling was carried out using the active adsorption technique. Sampling time was 1 h. Ambient temperature and traffic flow measurements were carried out during each sampling operation. The results indicate that average benzene concentrations at both sites exceed the limit value of 10 μg/Nm^3 established by the European Community （EC） （Dir. 2000/69）. Concentration levels of other BTEX are relatively high as well. A correlation between BTEX concentration and two wheeler vehicle flow was observed.

Blast responses of polyurea retrofitted utility tunnel reinforced with basalt fibre reinforced polymer bars

Polyurea coating and carbon fibre reinforced polymer reinforcing techniques were applied to retrofit a severely damaged urban utility tunnel(UUT).The blast responses of the retrofitted UUT were investigated through in-filed explosion experimental tests,and the displacements,strains,accelerations,and damage were compared.The retrofitted UUT exhibited comparable or even better blast resistance than the intact UUT.Although the polyurea coating was flexible,it exhibited excellent performance in improving the blast resistance of the damaged UUT.As the UUT reinforced with basalt fibre reinforce polymer(BFRP)bars has smaller damage compared with the UUT reinforced with steel bars,its retrofitting is simple,and the cost is low.The roof was simplified as an elastically simple support one-way slab.Euler beam theory was adopted to analyse the dynamic responses of UUT roof considering the interaction between soil and structure,which agree well with the experiments in the first three cases.

城市浅埋隧道自然排烟竖井临界间距研究

竖井间距会改变竖井内外压差,当竖井内外压差为0时,隧道火灾烟气将无法排出,此时竖井对应位置为竖井临界间距。由竖井内外口压差理论分析,给出竖井临界间距理论模型,再采用FDS模拟进行仿真验证。结果表明:设置竖井可明显降低隧道温度,竖井间距为临界间距时,温度下降幅度接近150℃,人员疏散路径温度低于60℃,竖井排烟效率在55%~80%,可有效进行竖井排烟;当竖井间距大于竖井临界间距时,隧道内烟气压强小于竖井出口处风压,竖井排烟效率低于50%。

城市交通隧道电动汽车火灾安全研究进展

城市电动汽车数量增加给城市交通隧道消防安全带来了新的挑战。论文首先归纳了隧道内电动车辆火灾研究的科学问题和关键技术问题,总结了电动汽车火灾成因及研究手段、火灾燃烧热特性、燃烧产物特性等领域的研究成果,分析了隧道狭长受限空间结构对电动汽车火灾发展过程的影响,探讨了城市交通隧道电动汽车火灾的消防救援。根据现行消防标准规范及隧道消防设计指南,讨论了应对电动汽车火灾交通隧道消防系统设计需要改进的要点。研究表明,新能源车火灾场景比燃油车火灾场景更复杂,主要表现在电池不稳定的喷射火源、持续时间、峰值热释放和峰值温度、汽车带电风险等方面。目前电动汽车火灾实体试验研究主要是在大空间或者开放空间中进行,隧道受限空间对电池燃烧特性影响、电动汽车火灾羽流特性以及有毒烟气蔓延及控制还缺乏系统性研究。研究成果能够为城市交通隧道的消防设计、安全运营以及应急救援预案制定提供参考。

城市连续隧道交织区主线交织车辆换道点选择行为研究

基于城市连续隧道交织区分析主线交织车辆换道点选择行为,以实地采集的车行轨迹数据为基础,利用随机森林模型分析主线车辆换道点选择行为特征及影响行为决策的影响因素,而后分别采用支持向量机模型与随机森林模型进行换道点选择行为决策建模和对比分析。研究结果表明:影响主线交织车辆换道点选择的主要因素为目标车辆状态以及本车道的后车状态,且经特征筛选之后建立换道决策模型的精度更高,其中支持向量机模型可以较好的刻画换道行为,模型的预测精度不低于85%。研究成果有助于在仿真模型中更准确描述换道点选择行为,同时为城市连续隧道交织区的优化和辅助驾驶策略制定提供支撑。

城市轨道交通超长隧道双车追踪模式下火灾烟气控制与人员安全疏散研究

[目的]城市轨道交通发车间隔一般较短,在超长隧道内会出现同方向行驶两列列车的情况,一旦发生火灾容易造成重大财产损失和人员伤亡,因此需对超长隧道双车追踪模式下的火灾烟气蔓延规律和人员安全疏散策略进行研究。[方法]采用FDS(火灾动力学模拟)软件和Path-finder软件,建立超长隧道火灾模型和人员安全疏散模型,对双车追踪模式下的火灾烟气蔓延规律,以及人员疏散进行仿真分析。[结果及结论]双车追踪模式下,前车尾部着火,通过临界风速纵向通风可保证前车火灾安全;火源下游烟气前锋的蔓延速度为3.20 m/s,至600 s时烟气蔓延至后车,620 s时烟气可完全覆盖后车;烟气温度沿隧道纵向衰减很快,且温度衰减符合双指数模型规律。双车追踪模式下,减小联络通道间距可减少人员疏散总时间,对人员疏散时离开列车的时间影响不大;开启列车端门和疏散平台一侧车门,可显著减少人员疏散时间。在超长隧道双车追踪的最不利火灾场景下,人员疏散存在困难,可通过减小联络通道间距保障人员疏散安全。

城轨项目基坑施工对综合管廊盾构井的影响分析

本文以广州市天河智慧城科韵路段综合管廊K4井为研究对象,进行临近城轨项目基坑施工对综合管廊盾构井的影响分析。利用岩土工程专用软件Midas/GTS进行有限元模拟,通过对关键施工步骤的数据统计,分析了临近基坑开挖对K4井地层位移、地连墙位移、内支撑轴力的变化及其影响规律,并提出了合理的建议和措施,保证了基坑的安全施工。

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.

软土地层盾构隧道管片上浮影响因素有限元分析

为了研究掘进速度和浆液凝胶时间对盾构隧道管片上浮的影响,依托苏州地铁5号线通园路站-星港街站盾构区间,采用Winkler弹性地基梁建立盾构管片三维有限元荷载结构模型,考虑同步注浆和二次补浆对管片产生的动(静)上浮力,分析掘进速度和注浆凝胶时间对管片上浮和错台的影响。研究结果表明:管片上浮和错台随着盾构掘进速度的增加而增大,上浮主要出现在浆液未凝固段管片底部,错台主要出现在浆液未凝固段与盾尾段和浆液凝固段的交界处,为避免管片上浮量和错台量超过规范要求,盾构掘进速度不能超过10环/d;随着浆液凝胶时间的延长,管片上浮量和错台量逐渐增大,选用速凝早强的双液浆进行背后注浆有利于控制盾构隧道上浮。