Tunnelling and Underground Space Technology最新文献

{"title":"Improving the effect of air chambers on micro-pressure waves from tunnel portals: Moderate underdamping","authors":"","doi":"10.1016/j.tust.2024.106016","DOIUrl":"10.1016/j.tust.2024.106016","url":null,"abstract":"<div><p>This research explores the ability of multiple small air chambers, distributed along railway tunnels, to suppress wavefront steepening and aims to find an effective method to prevent the radiation of unacceptable pressure disturbances from tunnel portals. It does so by utilizing the existing idle space in the tunnel, such as under walkways, and investigates the influence of moderately underdamped air chambers on wavefront evolution. This complements previous work, in which the chambers are assumed to be overdamped. In the early part of the paper, the validity of the numerical method used in this paper is verified through various means, including experiments with specially constructed air chamber model. Next, differences in the indicative influence of the wavefront, between underdamped and overdamped chambers, are compared. The asymptotic state of the wavefronts, in tunnels equipped with underdamped chambers, is then considered, along with a corresponding sensitivity study, centred on a specific base case. After that, the reasons for the large wavefront gradient caused by the underdamped chamber are discussed. Finally, the effect of installing a check valve at the chamber connection on wavefront evolution is explored. It is found that a moderately underdamped chamber may have a greater potential to suppress wavefront steepening to that of an overdamped chamber, especially for wavefronts with amplitudes up to 4 kPa. However, the presence of significant inertia at the chamber connection could result in the wavefront continuing to steepen for a distance of 2–3 km. Therefore, it is advisable to exercise more caution when employing underdamped chambers in shorter tunnels. While the check valve may have a certain degree of mitigating effect on wavefront steepening, but its impact is not significant.</p></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142006975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamics of in-station time within metro systems: Measurement and determining factors","authors":"","doi":"10.1016/j.tust.2024.106006","DOIUrl":"10.1016/j.tust.2024.106006","url":null,"abstract":"<div><p>Worldwide, people living in mega cities are increasingly dependent on metro systems. Their travel experience, however, has not been closely examined. In particular, travel time estimates often do not consider in-station time, which can be significant, especially at large interchange stations with multiple exits and platforms. This study represents a novel attempt to measure in-station time dynamics systematically, considering a wide range of factors such as station design and layout, passenger volume and interaction, and operational schemes. An agent-based modelling approach is used to simulate movement dynamics within metro stations. Then, a robust quantile regression model is built to capture the variability of in-station time and analyze the underlying factors. Four operation scenarios are simulated for the weekday peak, the weekday non-peak, the weekend peak, and a festival holiday peak at two major metro stations in Hong Kong. The findings reveal that the in-station time distribution is the longest during the festival holiday peak, followed by weekday non-peak, weekend peak and then weekday peak. The in-station time varies from 2.5 to 27.5 min, which represents up to 10 times of the in-vehicle time for metro trips within the urban core. Based on the findings, the study recommends both long-term measures, such as increasing the number and density of entrances/exits, and short-term measures, such as providing more escalators at entrances/exits, augmenting the number of inbound ticket gates, improving the experience of transfer passengers, streaming flows to escalators at platforms, and optimizing headways. By adopting these measures, the goal of improving in-station time and travel experience can be achieved more effectively. Overall, this study provides valuable insights into in-station time dynamics and highlights its importance in travel time estimations. This study makes a methodological contribution of developing an agent-based model that takes into account the total passenger experience in relation to the station design and layout, train schedules, operations management and passenger characteristics, such as the total volume, walking speed, trip origins, trip destinations and their interactions.</p></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142006880","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental study of flame morphological behaviors and wall heat flux profiles from an adjacent fire with different separation distances in a longitudinally ventilated tunnel","authors":"","doi":"10.1016/j.tust.2024.106025","DOIUrl":"10.1016/j.tust.2024.106025","url":null,"abstract":"<div><p>An understanding of sidewall incident heat flux exposed to an adjacent fire source is important for evaluating flame wall interactions and the performance of structural systems in longitudinally ventilated tunnels. This work experimentally investigated the total heat flux profiles from an adjacent fire to a tunnel wall surface under the action of longitudinal flow velocity ranging from 0 to 2.5 m/s. A total of 192 tests were conducted, in which the separation distances between the fire and sidewall were also varied (5∼15 cm). Square sand-filled burners with dimensions of 5 and 10 cm were placed near the wall at four heat release rates (11.67, 17.43, 23.33, and 29.16 kW) to generate buoyant-controlled diffusion flames, and gaseous propane was employed as the fuel. Flame morphological behavior was recorded by two digital cameras from both the side view and downstream view. The heat flux profiles on the sidewall surface were measured by a total of 48 heat flux gauges. The flame transition behavior from persistent touching-wall flame to non-touching conditions, was discussed based on the analysis of the interactions among the longitudinal flow inertia, buoyancy and pressure thrust. The heat flux mappings of the wall surface were obtained for different burner-sidewall distances and heat release rates, which were consistent with the flame morphological behavior. The location of the peak heat flux migrated downstream at lower heights with increasing longitudinal flow velocity. In still air, the peak total heat fluxes upon the wall surface decreased with increasing separation distance, and raised with increasing heat release rate. Then, a correlation of the peak heat flux in still air was developed to describe the data well in the current work. While peak total heat fluxes presented an earlier increasing and later decreasing trend with a modified Froude number <em>u</em>²/<em>gS</em> under the effect of longitudinal flow velocity, which was well interpreted based on the change in radiative and convective heating effects on the wall surface, together with the cooling effect caused by forced flow.</p></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142002225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Three-dimensional numerical analysis of twin tunnelling in two-layered soil strata","authors":"","doi":"10.1016/j.tust.2024.106028","DOIUrl":"10.1016/j.tust.2024.106028","url":null,"abstract":"<div><p>Tunnelling induces stress change and displacement in the ground. The excavation of a new tunnel in stratified soil can trigger different patterns of stress redistribution, which may adversely influence nearby tunnels. Research on multi-tunnel interaction has mainly been performed on the assumption of a uniform ground. The effects of different soil stratifications on tunnelling interaction remain poorly understood. In this paper, three-dimensional numerical parametric studies verified by previous centrifuge tests were carried out to analyse the twin tunnelling effects in two-layered soil. An advanced hypoplastic constitutive model that can capture stress-, path-, and strain-dependency of soil behaviour is adopted. Numerical cases investigated include perpendicular twin tunnelling in two sand layers with different relative densities and the location of the interface between the two sand layers. It is revealed that larger settlements and a wider surface settlement trough occur when tunnelling in two-layered soil strata than in a uniform ground. This is because of the wider and larger soil arch induced in two-layered soil strata. The structural response including tunnel deformation, induced bending moment, and induced hoop stress of the existing tunnel can be greater when tunnelling in layered soil strata than in a uniform ground owing to larger stress relief. Moreover, the combination of bending moment and hoop stress can exceed the M−N failure envelope of the structure in layered soil. A conventional simplified assumption of a uniform ground can underestimate of the influence of new tunnel excavation on existing tunnels, resulting in unsafe designs.</p></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141998294","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Shaking table test for near-valley underground station: Influence of diaphragm walls","authors":"","doi":"10.1016/j.tust.2024.106030","DOIUrl":"10.1016/j.tust.2024.106030","url":null,"abstract":"<div><p>Diaphragm walls are commonly employed as a permanent support for the building of metro stations near urban valley, and in conjunction with the interior sidewalls of the station structure to withstand the pressure from surrounding soils. Despite their prevalent use, the effect of underground diaphragm walls on the seismic response of stations is not yet fully understood. In this paper, a series of 1-g shaking table tests is designed to investigate the seismic response of a near-valley station with underground diaphragm walls within the elastic range. Modeling the stratum-structure-diaphragm walls system is accomplished by employing granular concrete reinforced with galvanized steel wires and synthetic model soils, and a station without diaphragm walls is included, serving as a benchmark for comparative analysis to understand the influence of diaphragm walls on the seismic behavior of the station. The experiment was designed for three depth-to-width ratios (DWRs), i.e. 1/3, 1/4, and 1/8, of arc-shaped valley topography, as well as the seismic excitations for the test include actual seismic records with the amplitude of 0.2 g, 0.4 g, and 0.8 g, respectively. Results show that the underground diaphragm walls enhance the lateral stiffness of the near-valley station compared to structures without diaphragm walls, and thus significantly reducing the racking deformation of structure during earthquakes. The presence of diaphragm wall would decrease the amplification of dynamic earth pressure caused by valley effect at the structural sidewalls, and significantly reduce the lateral vibration and shear effect of the station near a valley with a larger DWR. Notably, bending moment response at the connection between the diaphragm walls and structural sidewalls are dramatically amplified under strong seismic loading, and such adverse effects gradually increase with the DWR of the valley.</p></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141992636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical study on rock blasting assisted by in-situ stress redistribution","authors":"","doi":"10.1016/j.tust.2024.106022","DOIUrl":"10.1016/j.tust.2024.106022","url":null,"abstract":"<div><p>During tunnel blasting at deep depths, the rock mass is frequently subjected to high in-situ stress. Except for explosive detonation, the in-situ stress itself, particularly the stress concentration due to stress redistribution, also possesses the potential to cause rock fracture. Then there is a possibility of utilizing the stress redistribution to assist rock fragmentation during blasting. However, this concept has not garnered sufficient attention and systematic research in the field of tunnel blasting. The present study numerically investigated the rock fracture resulting from blasting with assistance of stress redistribution under various in-situ stress conditions with a focus on the full-face blasting of a deep circular tunnel. Based on the numerical modeling, the blasting parameter change required to maximize the auxiliary effect of in-situ stress redistribution was discussed. The results show that blasting of the previous round of blastholes creates a temporary cavity that induces in-situ stress redistribution. The redistributed stress generates cracks in the rock mass assigned to blasting of the current round of blastholes, particularly under high and anisotropic in-situ stress as well as large cavity conditions. The presence of these pre-generated cracks, together with their enhanced reflection of explosion stress waves, contributes to an increase in the degree of rock fragmentation during blasting. By utilizing the auxiliary effect of in-situ stress redistribution, there is a significant reduction in the amount of explosive required, with a saving of up to 30% demonstrated in the used computation example. The assistance of in-situ stress redistribution on rock blasting is particularly pronounced in the rock mass aligned along the orientation of minor principal stress and with larger cavities. As a result, increasing the blasthole burden in the orientation of minor principal stress and equipping the blastholes in the outer rounds with a larger burden contribute to maximize the auxiliary contribution of in-situ stress redistribution and expand the scope of rock fragmentation during blasting.</p></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141993666","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Distributed fibre optic sensing and novel data processing method for tunnel circumferential deformation – A case study of an ageing tunnel at CERN","authors":"","doi":"10.1016/j.tust.2024.106014","DOIUrl":"10.1016/j.tust.2024.106014","url":null,"abstract":"<div><p>The European Organization for Nuclear Research (CERN) is one of the largest nuclear research centres in the world, operating the most powerful particle accelerator housed in a massive 80 km-long underground tunnel network. Over the decades, regular site inspection has observed the ongoing development of structural defects, such as widened cracks, water infiltration and misalignment of the particle accelerator beamline caused by differential tunnel floor settlements. Such ongoing tunnel deterioration necessitates long-term field monitoring and assessment of the continuous deformation behaviour of the tunnel lining. Recently, distributed fibre optic sensing (DFOS) has emerged as a promising tool for monitoring civil structures by providing spatially continuous strain measurements using fibre optic cables. Conventionally, a fibre optic cable can be continuously bonded onto a structure with a flat surface for continuous strain measurement (e.g., pile foundations, retaining walls). Nevertheless, to monitor tunnel circumferential movement, fibre optic cables usually can only be deployed at some discrete fixing points around a curved tunnel surface. The raw DFOS data obtained by this fixing-point method cannot be directly processed into continuous strain measurements due to the discrete nature of the installation. This poses a challenge for accurately analysing tunnel structural performance. To address the limitations of the fixing-point method, this paper presents an optimized data processing method for analysing DFOS strain measurements of curved circumferential tunnel behaviour at the CERN tunnel. The proposed method enables the determination of the actual stepwise strain profile between fixing points and its conversion into tunnel convergence by integrating along the path. The converted DFOS tunnel displacements offer a more realistic and intuitive representation of the tunnel deformation mode than the DFOS strain profile alone. Additionally, the results of tunnel displacement demonstrate agreement with convergence measurements obtained by the conventional total station method, indicating the enhanced capability of DFOS for existing tunnel monitoring and assessment. The DFOS method has the potential to provide highly accurate deformation measurements, with a much higher resolution than the typical measurement accuracy, for example, by total stations.</p></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0886779824004322/pdfft?md5=f1fab02d9778dc42a14b7ee237b3b176&pid=1-s2.0-S0886779824004322-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141990472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental response of a fusible PVC pipe with service connections to axial pullout","authors":"","doi":"10.1016/j.tust.2024.106018","DOIUrl":"10.1016/j.tust.2024.106018","url":null,"abstract":"<div><p>This paper investigates the axial pullout response of a fusible polyvinyl chloride (FPVC) main pipe with two service connections. A large-scale pullout experiment in dense sand was conducted to investigate the behaviour of service lines to axial pullout of the main pipe and the impact of service connections on the main pipe’s axial pullout resistance, axial force distribution, and moment distribution. The study assesses the response of both crosslinked polyethylene (PEX) and copper service lines as well as the role of goosenecks. Distributed fibre optic sensors (DFOS) have provided insight into the strain distributions along the main pipe and service lines. The experimental results have shown that service connections significantly increase the axial pullout resistance of the main pipe when compared to a previous test on an identical pipe without service connections. The movement of the service connections was found to reduce the earth pressure in a region behind the service connection. Hinging of the service saddles was observed to result in single curvature bending of the service lines. DFOS data along the main pipe has been used to approximate the individual load-displacement responses of the PEX and copper service connections.</p></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S088677982400436X/pdfft?md5=ef7f87a7db42252488bda48fbf4f9d44&pid=1-s2.0-S088677982400436X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141990470","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Model test and numerical verification of surrounding rock stability of super-large-span and variable-section tunnels","authors":"","doi":"10.1016/j.tust.2024.106020","DOIUrl":"10.1016/j.tust.2024.106020","url":null,"abstract":"<div><p>There are great risks and difficulties during the construction of super-large-span and variable-section tunnels, as it is very easy to cause tunnel rock instability, landslide, roofing and other accidents. Through the case of Qizishan Tunnel Project, the second phase of Suzhou International Rapid Logistics Corridor, a model test system has been established for the mechanical effect study of the construction of super-large-span and variable-section tunnels. The construction has been simulated of the tunnel’s multi-arch section turning to large-span and variable section in this paper. In this way, the mechanical effect of super-large-span and variable-section road tunnel construction has been explored. Based on the monitoring data, the overall mechanical response and the stress change of the surrounding rock in the tunnel space have been studied during the change of construction section. By monitoring the deformation and stress change of the surrounding rock, the deformation and stress release mechanism of the surrounding rock has been revealed during the construction of super-large-span and variable-section tunnels. The results of the study show that the bias pressure caused by the geometric asymmetry at the variable section of the tunnel makes the lining stress at the right sidewall relatively large. The excavation of the upper step has a great impact on the vertical displacement of the surrounding rock at the tunnel vault, and the settlement change of the vault caused by the excavation of the left half of the upper step is smaller than that of the right half. The vault settlement reaches the maximum when the excavation passes through the monitoring section of the variable section. The upper step supports the surrounding rock at the vault, and the remaining excavation steps have little effect on the settlement of the surrounding rock at the vault. The numerical simulation results of super-large-span and variable-section tunnels are basically consistent with the deformation law of surrounding rock in the model test results, which shows good accuracy of the model test.</p></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141990471","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ground-tunnel geological prospecting and treatment methods of small-diameter TBM crossing shallow buried water-rich tunnel: A case study","authors":"","doi":"10.1016/j.tust.2024.106024","DOIUrl":"10.1016/j.tust.2024.106024","url":null,"abstract":"<div><p>Water inrush disasters occurred many times when the small-diameter TBM of Yinchaojiliao Project passed through the shallow water-rich section. The effective detection and timely treatment of the water structures ahead of the tunnel face of small diameter TBM is very important to ensure the safe tunneling of TBM. In order to avoid the recurrence of water inrush disaster, the ground-tunnel geological prospecting and treatment methods is put forward. The ground-tunnel prospecting methods include the ground ERT and the tunnel resistivity are established. The ground electrical resistivity tomography (ERT) is used to detect the shallow water-rich tunnel section of small-diameter TBM in advance, and the resistivity range ahead of the tunnel face is obtained, which provides an initial model for the data inversion of tunnel resistivity method. Through the detection results of tunnel resistivity and ground ERT methods, the position of water-bearing structures ahead of the tunnel face is comprehensively judged on the basis of geological analysis, which provides the scope and depth of treatment for small-diameter TBM crossing shallow water-rich tunnel. The ground grouting is used to grout and plug the water-bearing structures range and depth delineated by the advanced detection. At the same time, the chemical grouting is used to plug the water outlet point in the tunnel. Through the above measures, the small-diameter TBM successfully passed through the shallow buried water-rich tunnel section. This paper provides a valuable reference for similar projects through the case study of small-diameter shallow-buried water-rich tunnels in Inner Mongolia, China.</p></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":null,"pages":null},"PeriodicalIF":6.7,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141985314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}