Tunnels are an integral part of the transportation system playing a significant role both in people and freight transportation. Many countries around the world have developed hundreds of kilometres of these channels and networks connecting different points passing through plains and areas having varying slopes and also potential natural obstructions. The focus on tunnel safety has increased significantly over the years pertaining to various catastrophic accidents. In case of a fire inside the tunnel, hot smoke and combustion products rise and reach the ceiling, wherein depending upon the ventilation conditions, either are pushed outside the tunnel or lead to a phenomenon of reverse flow in the direction opposite to the ventilation thrust called as backlayering with the minimum ventilation velocity needed to prevent this flow called as the critical velocity. The current work analyses the ventilation requirements for Khor Fakkan Tunnel (KFK) situated in the United Arab Emirates, passing through the Hajar mountains, and is verified using both the 1D and 3D analysis with the softwares – IDA Tunnel and ANSYS Fluent. The section TK1 of the KFK tunnel is focussed, wherein critical sections are identified pertaining to wind and stack effects and the thermal and visibility parameters are evaluated in coherence with the NFPA 130 standard. A preliminary study is carried out where the critical velocity is calculated using both the NFPA 502-2017 and NFPA 502-2020 standards for the two fire sizes selected based on the NFPA 92 standard. The results of the 1D analysis provide the groundwork for the CFD simulation and the modelling is carried out to visualize the varying gradients of both the temperature and velocity. The results reveal the existence of the backlayering phenomenon inside the tunnel with the ventilation velocity being lower than that of the minimum needed. The thermal properties along the egress pathway for evacuation are also checked so as to ensure tenability along the route of escape.
Le gallerie sono parte integrante del sistema di trasporto e ricoprono un ruolo fondamentale sia per il trasporto passeggeri che per quello delle merci. Molte nazioni in tutto il mondo hanno sviluppato centinaia di chilometri di rete e gallerie per connettere aree differenti, passando per zone pianeggianti, con diverse pendenze e anche potenziali ostacoli naturali. L’aspetto della sicurezza ha acquistato notevole importanza durante gli anni, a seguito di incidenti catastrofici. In caso di incendio all’interno di una galleria, i fumi e i prodotti di combustione raggiungono il soffitto dove, in base alle condizioni di ventilazione, sono spinti all’esterno o generano un fenomeno di flusso inverso, chiamato backlayering, in direzione opposta al flusso di ventilazione. Per evitare questo fenomeno è richiesta una velocità minima di ventilazione, chiamata velocità critica. Questo elaborato analizza i requisiti di ventilazione per il Khor Fakkan Tunnel (KFK), situato negli Emirati Arabi Uniti e tra le montagne Hajar, utilizzando analisi 1D e 3D con i software IDA Tunnel e ANSYS Fluent. In particolare, è stata presa in considerazione la sezione TK1 della galleria KFK, dove sono state identificate delle sezioni critiche circa gli effetti del vento e l’effetto camino. Sono stati analizzati sia i parametri termici che di visibilità, in accordo con quanto previsto dalla normativa NFPA 130. È stato effettuato uno studio preliminare dove è stata calcolata la velocità critica utilizzando le normative NFPA 502-2017 e NFPA 502-2020, considerando due diverse dimensioni di incendio come riportato nella normativa NFPA 92. Il risultato dell’analisi monodimensionale (1D) ha fornito la base di partenza per la simulazione CFD, quindi è stata effettuata una modellizzazione che ha permesso di visualizzare le variazioni dei gradienti di velocità e temperatura. I risultati ottenuti hanno evidenziato l’esistenza del fenomeno di backlayering all’interno del tunnel con velocità di ventilazione inferiori alla minima richiesta. Sono state verificati anche gli aspetti termodinamici per quanto riguarda la sicurezza delle vie di fuga in caso di evacuazione.
Design analysis for the emergency ventilation requirements of railway tunnels. The case study of Khor Fakkan tunnel
SHAIK, MUHAMMAD RIZWANULLAH
2019/2020
Abstract
Tunnels are an integral part of the transportation system playing a significant role both in people and freight transportation. Many countries around the world have developed hundreds of kilometres of these channels and networks connecting different points passing through plains and areas having varying slopes and also potential natural obstructions. The focus on tunnel safety has increased significantly over the years pertaining to various catastrophic accidents. In case of a fire inside the tunnel, hot smoke and combustion products rise and reach the ceiling, wherein depending upon the ventilation conditions, either are pushed outside the tunnel or lead to a phenomenon of reverse flow in the direction opposite to the ventilation thrust called as backlayering with the minimum ventilation velocity needed to prevent this flow called as the critical velocity. The current work analyses the ventilation requirements for Khor Fakkan Tunnel (KFK) situated in the United Arab Emirates, passing through the Hajar mountains, and is verified using both the 1D and 3D analysis with the softwares – IDA Tunnel and ANSYS Fluent. The section TK1 of the KFK tunnel is focussed, wherein critical sections are identified pertaining to wind and stack effects and the thermal and visibility parameters are evaluated in coherence with the NFPA 130 standard. A preliminary study is carried out where the critical velocity is calculated using both the NFPA 502-2017 and NFPA 502-2020 standards for the two fire sizes selected based on the NFPA 92 standard. The results of the 1D analysis provide the groundwork for the CFD simulation and the modelling is carried out to visualize the varying gradients of both the temperature and velocity. The results reveal the existence of the backlayering phenomenon inside the tunnel with the ventilation velocity being lower than that of the minimum needed. The thermal properties along the egress pathway for evacuation are also checked so as to ensure tenability along the route of escape.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/167399