SLBC Tunnel Work Likely to Resume Next Month

Hyderabad: Resumption of work on the Srisailam Left Bank Canal tunnel could begin next month, or latest by November, and advanced tunneling methods using explosives that will be triggered by delayed detonators are to be used to complete the balance of around 9 km of the tunnel work.

It is learnt that basic geophysical studies at the ground level have been done to ensure that once work resumes, it can be done safely and avoid disasters like the one on February 11 when a portion of the tunnel roof collapsed resulting in the death of eight workers, six of whose bodies have not been found so far.

To avoid the shear zone and soft rock portions at the collapsed site, plans have been made for a ‘transition curve’, in the tunnel alignment which will see a sideways digging towards the left from the existing tunnel face where the collapse occurred.

It is learnt that this bypass could be around 300 metres and once it crosses the soft rock zone, it will realign with the original designed path of the tunnel.

Since the work from now on will follow the drill and blast method, the tunnelling will be different from that which was done until February when a tunnel boring machine was being used.

The blasting will start at the top of the tunnel and once the rock debris is removed, then the lower sections of the rock will be tunnelled through to ensure safety, which will be monitored continuously with supports set up to prevent any rock fall or collapse as the work progresses further, it is learnt.

The existing conveyor belt system will also be extended as required and will be used for debris removal, and the rest of the studies, including an aerial geophysical survey are expected to be completed by the end of this month.

Government has drafted plans to restart work at the Srisailam Left Bank Canal tunnel

· Basic geophysical studies at the ground level completed for safety.

· Aerial geophysical survey expected to be completed by September-end.

· New tunnel portion to have 300-metre bypass to avoid disaster-hit spot.

· Work to follow the drill-and-blast method as against the use of a tunnel boring machine earlier.

· Conveyor belt system will be extended as required.

· 8 killed in tunnel collapse on February 11, bodies of six victims not found so far.