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Title: Fire safety in existing road tunnels and confined spaces of Hong Kong
Authors: To, Chi Wing
Degree: Ph.D.
Issue Date: 2020
Abstract: In Hong Kong, buildings and other structures are statutorily required to provide active and passive fire safety provisions as prescriptively stipulated in different Codes and Standards that are in-forcing during the time of construction. However, these designs might not be able to cater for new challenges caused by technology advancement, living habits changes, use of new vehicular construction materials as well as increases in population and traffic volumes. In this thesis, new challenges faced by road tunnels nowadays would be elaborated in detail. Fire safety provisions in tunnels were reviewed. A horrible fire that happened in 1999 at the Mont Blanc Tunnel caused 39 decreases. The fire was originated from a heavy good vehicle carrying flour and margarine. Post-fire investigation revealed the fire temperature was over 1,300°C and cause extensive structural damage in the tunnel. 15 days were required for cooling down the tunnel to allow the entry of investigation team. Countless serve road tunnel fires had claimed the lives of people and caused huge monetary loss. Having learnt from the tragic experience of road tunnel fires, researchers suggested that a tremendous amount of heat would be released in a heavy goods vehicle fire occurs inside a road tunnel. Means must be provided for tunnel structure protection and fire spread prevention; while the installation of fixed fire-fighting system is a feasible solution to the problem. In the first part of the thesis, the integrated performance of fixed water-based fire-fighting systems and a longitudinal ventilation system was studied by performing full-scale burning tests. A section of tunnel under construction, with dimensions of 100m in length, 12m in width and 6.5m in height, was utilized for the venue of full-scale burning tests. Water-spray systems, with or without AFFF foam additives, were used to suppress a 20MW fire in different testing scenarios. The longitudinal ventilation was set at the critical velocity, i.e. a wind speed of 3ms-1. Diesel or wood pallets were used to fire fuel. Temperature profiles, both in upstream and downstream positions, would be studied and compared. Video camera would also be used to record the development of fire and as well as the movement smoke. Top shield and side shield would be provided to simulate the shielding effect of vehicle compartment and adjacent tall vehicle respectively. A total of eight scenarios with different testing parameters combinations would be conducted for evaluating the coupled performance of water-spray fire-fighting systems and longitudinal ventilation, the activation sequences of these two systems and the shielding effects. These results would be valuable for formulating statutorily requirements on fixed fire-fighting systems and provide a solid scientific foundation on the holistic assessment in the engineering analysis for road tunnels. Moreover, the introduction of clean fuel for vehicles also posted new challenges to the road tunnel design. In the second part of the thesis, the explosion and thermal hazards associated with the clean fuel vehicles would be studied through Computational Fluid Dynamics software, namely Flame Acceleration Simulator (FLACS) in a garage and a section of short vehicular tunnel. A garage with a design commonly seen in Hong Kong was used to demonstrate thermal hazards of vehicles using LPG and hydrogen as fuel. The simulation results on post-explosion pressure and temperature surges could provide in-sight on determining appropriate protection measures for the maintenance garage. Furthermore, a section of SVT of 12m in length with concealed spaces under the roadways was used to illustrate the explosion hazards of LPG vehicles which further highlighted the problem regarding old / existing designs might not be able to cater for new challenges. Two case studies in road tunnels of Hong Kong were used to intensify the idea. According to the findings, a recommendation was made to strengthening fire safety management as an interim measure. Through continuous dynamic risk assessment, potential risks and areas requiring strengthening could be identified while the use of performance-based design provides a scientific platform to holistically review the integrated performance of existing active and passive fire safety provisions as well as their synergy with enhanced and tailor-made fire safety management measures.
Subjects: Tunnels -- Fires and fire prevention
Tunnels -- Safety measures
Roads -- Design and construction -- Safety measures
Traffic safety -- China -- Hong Kong
Hong Kong Polytechnic University -- Dissertations
Pages: xv, 179 pages : color illustrations
Appears in Collections:Thesis

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