Tunnelling began on the three-line network in July 2014 and 21 TBMs have been used to drill and line 111km of tunnels, using 470,497 concrete segments to form 70,071 tunnel rings.
Tunnelling was completed on the Green Line in April with a breakthrough at Education City station, while the final section of tunnel on the Gold Line was holed through at Msheireb station in May.
Qatar Rail says the construction of the Doha metro is now 50% complete. In addition to the tunnels, 7.5km of viaducts have been completed and foundations have been constructed at 33 stations.
A full-size mock-up of the Kinki Sharyo metro train for Doha will be unveiled before the end of the year.