Cast Lining at the Legacy Way Tunnel Cross Passages
Brisbane’s Legacy Way tunnel is a 4.6 km long twin tube TBM driven road tunnel. Transcity, a joint venture between Brisbane-based BMD Constructions, Italian tunnelling company Ghella and Spanish tunnelling and civil infrastructure company, Acciona Infrastructures won the design and construct contract. Two 12.4 m double shielded Herrenknecht TBMs excavated the tunnel in record breaking time, achieving 30 day maximums of 787.8 m and 818.9 m respectively and total time of 6 months and 9 months for each TBM drive.
The Transcity JV won the 2013 ITA tunnelling award category Major Tunnelling Project of the Year (Over $500M) for the Legacy Way tunnel, which is due for completion in 2015.
The two tunnels are connected by 37 underground cross passages, spaced every 120 metres along the length of Legacy Way. Each passage is 4 metres wide, 3.5 metres high and 10 metres long. Excavation consisted of rock hammer, road header and where necessary drill and blast. Ground support comprised a temporary steel or synthetic fiber reinforced shotcrete lining, followed by a cast in situ synthetic fiber reinforced permanent arch lining.
Following form work set-up, the permanent arch lining was poured in one 8 to 12-hour shift. The arch lining was up to 1m thick in places and solely reinforced with 4 kg/m3 of Elasto Plastic Concrete’s Barchip synthetic fiber reinforcement. Design specification called for a maximum crack width of 0.2 mm. FEA Analysis undertaken by Barchip and on-site in-situ trials undertaken by Transcity combined with 12-hour and 3-day beam testing showed that Barchip’s synthetic fiber reinforcement was able to meet the design specification.
Barchip synthetic fibers are capable of meeting high performance design requirements without any of the problems normally associated with traditional steel reinforcement. Barchip’s fibers eliminate the need to set up steel mesh, are less damaging to equipment and are non-corrosive, ensuring long term durability. Barchip synthetic fiber concrete reinforcement do not suffer embrittlement, minimise maintenance down time and are the highest performing fiber on the market at the lowest cost per joule.