Proceedings:
18th Australasian Tunnelling Society Conference
Publication Date:
Nov 2023
Authors:
Nick Agnew, Zavlangas, D. and Miles, P.
The project invested in fire testing to understand the HDPE combustion hazard during construction, and to assess the benefits of water mist suppression as a potential risk mitigation measure. It was found that the material was difficult to ignite and did not promote fire spread. Misting was demonstrated to be effective at suppressing a fire involving HDPE liner.
Outcomes of the testing informed a wider risk assessment. A suite of engineering and operational controls was developed. To complement “business as usual” measures, other novel controls were implemented, including a misting system behind the TBM trailing gear and innovative misting “fire breaks” distributed along the length of the tunnel at 1500 m intervals.
With the efforts made to minimise the hazard of fire and the potential for localised flashover and spread, and to facilitate self-evacuation, it was concluded that the plastic liner materials do not unacceptably increase risk to life or asset, relative to other tunnels without a combustible liner.