Soft Rock Problems Force Rethink on SLBC Tunnel
Officials consider alternative routes to avoid fault zones and ensure safe project completion.
Hyderabad: The February 22 collapse of a section of the SLBC tunnel in the Nagarkurnool district has prompted serious discussions on drafting a plan to prevent repeat incidents of a similar nature in the future, including digging bypass tunnels.
The SLBC tunnel is being dug simultaneously from two sides – Tunnel-I, which is the inlet near the Srisailam reservoir, were the collapse occurred, and Tunnel-II, which is the outlet end in Nalgonda district.
The plan that is being talked about is stopping digging the tunnel along the current alignment as there are serious and legitimate fears that the machines and the workers could encounter more fault, or shear, zones that may result in further collapses.
Of the 44-km-long tunnel, stated to be the world’s largest when completed, just around 10 km remains to be dug. Following the collapse at the Tunnel-I side, sources said there was concern over the presence of rocks along the route.
Instead, the digging of two bypass tunnels, each five metres wide, is being considered. These tunnels will be dug in the hard rock portion under the Nallamala hills where the SLBC tunnel is being built.
“This proposal will have to be fully studied. Geological studies will be required to be done by the likes of NGRI and GSI. This will take some time but it is an option that is being looked at so that the project can be completed safely,” a government official said.
Meanwhile, officials said teams from NGRI and GSI were continuing their overground study on the location inside the Amrabad tiger reserve on top of the spot where the tunnel collapsed.
