The two NFM machines driving parallel tubes for the Shiraz metro, in Iran, achieved first hole throughs in late February. Arriving at the partly built open box cut for Station No 6 (Zahra Blvd) on 21 February and 26 February, respectively, the 6.88m diameter EPB TBMs are under maintenance and should be re-launched in early April.
While they finished almost neck-and-neck, the first of the TBMs began boring in September 2004 and the second machine three months later. They bored from the launch box that will later become Station No 1 (Gol e Sorkh Sq), at Allah Square near Shiraz international airport.
Over the twin 4.7km drives contractor Bamrah Construction achieved a best weekly advance rate of 117 rings with the second TBM, and 21 rings in a day with the first TBM. The 300mm thick rings (5+1 segments), manufactured using moulds supplied by CBE of France, give a finished internal tunnel diameter of 6.0m.
Cover to the tunnel crown ranges from about 7.5m to 16.5m. Geology along the route passing through silty clay and dense clayey gravel with silt and sand, and there are several pressurised lenses of sandy silt, silty sand and fine grained gravel.
The TBMs will each excavate a total of 14km for the new metro line, which also includes cut and cover, NATM and at grade works. Consultant for the civils works is local firm Omran Mohit Zist.
The entire line runs 24.1km from the south east to the north west of the city in Fars province, via 21 stations. Shiraz Urban Railway Organization (SURO) plans to open the line in 2009.
