10. Nezam Abad Metro Station (Earth Works & Retaining Structure)
General Technical Specification of the Project:
Principally the main operations related to this project include preparing the site of the station for excavation and implementing the retaining structure. Due to the depth of excavation, around 30m, a main and complementary retaining structure is needed. The main retaining structure is consisted of piles with 1m diameter which are located all around the station. Before concrete work, a reinforced bar with metal profiles is located inside these piles. Then with excavation work in each level braces are installed such as lateral brace, straight (horizontal brace), and truss (end brace). For preventing the local weathering, lateral walls were concreted. By destroying prefabricated paries of tunnel and excluding them to the final level, excavation operation and retaining structure was finished.
Temporary Decks Installation on Station:
Metal decks are installed after excavating in order to conserve the access to streets in upper levels of the station. Due to the height of the decks (18-25m) and the traffic of heavy vehicles, vibration originates around the station. But by installing junction parts between decks and heavy asphalt, vibrations were reduced.
Demolition of Tunnel Segment:
Before installing station operations, Tehran's metro lane 2 tunnels were done by a boring machine. Paries of this tunnel was made of high strength prefabricated concrete segments.