New Delhi:

IIT Delhi professor Dr Jagdish Telangrao Sahu, who is a member of the high-level government committee that framed guidelines for tunnel construction, design and maintenance, spoke to NDTV on the tunnel crisis.

Dr. Jagdish Telangrao Sahu said that we have to pay more attention to the side investigation, that is, the place where the excavation is being done. It should be found out what kind of stones are there. What is its structure, there are no loose stones, there is no fault there. We do not know many things at the time of excavation. All this should be ascertained before digging. All these things should be included in the design input, taken seriously during the preparation of excavation.

He said that the stones in the Himalayan region are quite deceptive, because their type changes at a distance.

Dr. Sahu said that during the construction of the tunnel, two aspects are important. Before digging, you can gather information through side checks, non-destructive testing, or through bore holes. The second aspect is the design that we do with the method of building the new Austrian tunnel. If you do it through this, you also keep taking feedback mechanisms during excavation. If there is a loose stone somewhere, you modify the design of that place. Feedback loop tunneling is necessary during tunnel construction, which is not being followed right now.

"We have to do the ground investigation in a more detailed manner before digging," he said. Side checks should be very informative. Apart from this, we should also do hydro-geological surveys along with it. On the other hand, when we dig tunnels, we should take safety measures seriously. For example, there may be an escape tunnel at the time of excavation, along with a small hume pipe if the tunnel is small. All this should be mandatory for tunnel construction.

Dr. Sahu said that NHAI's decision to audit all under-construction tunnels is right, it is a good lesson after the accident. Also, railway tunnels and hydropower tunnels should also be audited. The tunnel is a risk India venture, but if side investigation is done well, then the risk can be reduced.

In this case, there was no Scape Tunnel, which is unfortunate. The scape tunnel is not necessary during the construction of a small tunnel, but we should have safety options such as pipes.