Safer to do horizontal drilling to rescue labourers trapped in Silkyara tunnel: Experts

It will be safer to do horizontal drilling to rescue the 41 labourers trapped inside the Silkyara tunnel in Uttarkashi, a former GSI official said on Tuesday.

Tribhuwan Singh Pangti, who retired as the additional director general of the Geological Survey of India (GSI) told PTI that the disaster could have been averted had the construction company prepared a pilot tunnel first to study the rock mass of the area and installed a proper support system.

It will be safer to do horizontal excavation to save the 41 labourers trapped inside the tunnel for 10 days but if vertical excavation is to be done, it should be started from a point where the depth is minimum, Pangti said.

When rescue operations are carried out in a tunnel, certain set standards of safety must be kept in mind, he added.

Rescue operations are being carried out on a war footing since portions of the tunnel collapsed following a landslide early on November 12, leaving the workers trapped behind a huge mound of debris.

The Silkyara tunnel, about 30 km from the district headquarters of Uttarkashi and a seven-hour drive from the Uttarakhand capital Dehradun, is part of the ambitious Char Dham all-weather road project of the central government.

''The Silkyara disaster is the result of excess blasting in tunnel excavation, ignoring experts' opinion and a negligent attitude towards maintaining safety, standards,'' Pangti said.

''The company did not even install necessary instruments in the excavated part of the tunnel which also contributed to the present crisis,'' he added.

The high-performance machines which were brought from Delhi and Indore, Madhya Pradesh, after the incident and delayed the rescue efforts could have been kept on stand-by and pressed into service immediately after the tunnel's partial collapse, Pangti said.

Citing his 37 years of experience as a geologist with the GSI, Pangti said in seismically active regions like the Himalayas, geology becomes significant and to begin any infrastructure or communication projects in such areas, a thorough knowledge of its geological situation is essential -- a fact which seems to have been neglected in this project.

This disaster could have been avoided if the construction company had prepared a pilot tunnel first to study the rock mass of the area and installed a proper support system, Pangti said. A pilot tunnel is excavated over a larger tunnel to explore ground conditions.

''The private companies that are coming to construct road tunnels, communication or hydro projects in the Himalayan region, don't conduct a prior analysis of the geological and tectonic situation of that particular place, that is why several such projects are failing,'' he said.

In the Himalayan region, the geological formation varies at different locations. So designs of projects should be prepared according to the rock formation of that particular area, said Pangti.

A detailed geological and glaciological study of the Himalayan region must be done before launching any infrastructural project in the region, he said.

''Though tunnels are a viable option to construct roads in the region, it should not be done without studying geological and glaciological conditions of a particular area,'' he said.

A committee of experts should be formed to study proposed infrastructural projects before giving them clearance, Pangti said.

Several measures are taken while constructing a tunnel to create a support system if an emergency exit is needed like cement grouting, rib support system, and rock bolting but in this case, all these safety norms seem to have been ignored, the former GSI ADG said.