New technology speeds up tunnel plans in Jammu and Kashmir

SRINAGAR: The first successful tunnel boring machine (TBM) operation to construct a 'head race tunnel' for a power project in Jammu and Kashmir has encouraged construction companies for faster execution of works. The news comes at a time when several tunnel projects are being planned in hills states including J&K, Himachal Pradesh and the northeast.

So far, drill and blast, and New Austrian Tunnelling Method (NATM), also known as Sequential Excavation Method (SEM), were used for building tunnels.

A spokesperson of infrastructure major Hindustan Construction Company (HCC), which is executing the 330 mw Kishanganga hydroelectric power project, said the tunnel construction will be completed on Tuesday.

The work for the National Hydroelectric Power Corporation ( NHPC) project involving Rs 2,726 crore started in 2007. HCC claimed power generation will start in 2016.

"We used two methodologies to construct the head race tunnel of six meter diameter. Of the 23.65 km tunnel, 14.75 km was constructed using TBM. The rest 8.9 km from the dam side is constructed using the conventional drill and blast method. We will have 'daylight break' (read completing tunnel) on Tuesday," said project manager Arackal Benny.

He added while the average monthly progress was only 100 meter on the other side using the conventional method, it was at least 400 meter on the stretch constructed using TBM. Benny said TBM method saved time and was safer.

"To make this successful, we ordered the suitable double shield TBM from Italy after different studies were carried out. Some of the features of the TBM had to be improved from its original design, such as increase in pushing and boring power," the HCC spokesperson said.

But it was not a completely smooth operation. After initial boring of 1.4 km, engineers faced a major challenge as the geology changed and loose soil was encountered instead of hard rock. These impediments were addressed to push the work.

Benny said the toughest task was to ensure that the tunnel being bored from both sides finally met. "We carried regular studies to ensure this. It was a tough task since the highest overburden under which TBM passed was over 1.4 km," he added.