THIRUVANANTHAPURAM: The Balaramapuram - Vizhinjam underground railway connecting Vizhinjam port to Balaramapuram railway station is being constructed using the New Austrian Tunneling Method (NATM), which is not much familiar in the tunneling industry in the country. This method, which revolutionized modern tunneling, has become the model for many tunnels around the world. NATM is considered to be the most suitable method for soils with the presence of limestone etc. The 9.2 km long single-lane tunnel will be shaped like a horseshoe when completed. Excavated soil, rock, etc. during construction can be reused during tunnel construction. Machinery used inside the tunnel can be moved back to other areas at any time.

Explosives for digging tunnel

Instead of trying to uniformly reinforce the entire tunnel wall, the method of reinforcement will depend on the structure of the tunnel rocks. The tunnel will be dug using explosives. At each stage, machines will be used to fill the area to be drilled with explosives. Small explosions will be made.

First in the Alps
NATM was first used for tunneling under the Alps. This method is also known as the sequential excavated method and sprayed concrete lining method.