With one TBM lost under debris, the second machine—awaiting repairs—must now complete the 10 km remaining.
Domalapenta: The collapse of a section of the SLBC tunnel, not only resulted in the now confirmed destruction of the tunnel boring machine (TBM), but it also means a yet-to-be-assessed delay in completion of the project to take 30TMCft of water from Krishna river from the Srisailam reservoir to the erstwhile Nalgonda district.
And amidst these unexpected turn of events, the second TBM, which has been stuck for the past few years waiting for spare parts to arrive so work can begin again, will have to do all the heavy grinding and lifting to complete the Srisailam Left Bank Canal tunnel project. All was going well with the original plan of digging the 44 km long tunnel from two ends with both TBMs expected to come face to face marking the completion of the tunneling works.
However, the TBM in Tunnel-I - the inlet side section beginning from Domalapenta village - having been all but destroyed as it lies in a mangled heap of 1,500 tonnes of steel and metal under tons of mud and rocks and has been reduced to the status of scrap metal, all hopes of the project’s completion now rest on the second TBM.
So far, between the two TBMs, around 34 km of the tunnel has been dug and another 10 km of tunneling is still left.
“There is no scope for a new TBM to replace the destroyed one,” one of the project’s engineers told Deccan Chronicle on Wednesday. The precast permanent lining segments made of cement concrete and steel that have been placed till where the TBM now stays ‘lost’ will have to be removed if a new TBM has to take the place of the old one, which will first have to be removed in bits and pieces. “The tunnel while digging, is wider than the 9.2 metre width of the completed structure. Removing the segments is out of the question as this can lead to more collapses. The only option is to use the other TBM to complete the job,” the engineer said.
The TBM in Tunnel-II, the outlet for the SLBC tunnel project near Teldevarapally village in Champapet mandal of Nalgonda district, has been waiting on the arrival of a critical spare, a giant bearing that is needed to repair the machine, so it can start working again. “That is still at the Chennai port and as of now, no one is thinking about it as everyone is focused on what happened here, and staff from that site have been deployed here in the wake of the accident to assist in rescue and recovery,” an official from Jaiprakash Associates, the company building the tunnel said.
