TBM excavation was imperative to the Doha Metro project; thereby minimizing any interference to the day-to-day lives of people working and living in Doha. In all, 15 Herrenknecht TBMs were ordered for the Metro project, 11 of which will be fitted with custom-engineered MineARC Emergency Refuge Chambers to provide an immediate safe-haven for workers requiring shelter in the event of a fire, a fall of ground, or similar emergency.
Each of the 11 MineARC Refuge Chambers can shelter up to 20 people for a minimum of 30 hours and features a number of important life support systems, including: primary and secondary oxygen supplies and a carbon monoxide/carbon dioxide scrubbing system to regenerate the air and remove the harmful chemicals as they build up thanks to the occupants own breathing activity.
It’s also vital that each chamber maintains positive internal pressure at all times – effectively sealing the chamber by preventing the ingress of potentially compromised air from the outside. Each refuge chamber therefore features an automatic overpressure system. Special sensors constantly monitor the relative pressure both inside and outside the refuge chamber, and relay this information to the chamber’s internal air systems. Based on the readings, a precise amount of air is periodically released into the refuge chamber, ensuring positive internal air pressure of at least 200 pascals above outside air pressure at all times.
All of these vital safety features ensure the chambers meet the very latest industry safety legislation pertaining to refuge chambers. This includes the current British Standard and the 2014 ITA Guidelines for the Provision of Refuge Chambers in Tunnels under Construction.
Phase 1 of the Doha Metro project is due for completion in 2018, and consists of four newly constructed sections: The 11 km twin-running underground section of Red Line North, the 16 km twin-running underground section of Green Line, the recently awarded 13.8 km twin-running underground section of Red Line South, and the 13 km twin-running tunnel of the Gold Line, the contract for which is expected to be awarded later this year.
Future scope for the Metro project includes the 17.5 km underground section of the semicircular Blue Line that will link Airport City and West Bay Central and the extension of the Green Line, which are both yet to get under way.