Context: Recently, an under-construction Silkyara-Barkot tunnel in Uttarakhand collapsed trapping 40 workers inside.

Issue

• About 40 workers are trapped inside a tunnel after the under-construction tunnel structure collapsed in Uttarakhand on November 12.

• The workers are trapped in the Silkyara Tunnel located on the Uttarkashi-Yamnotri Road.

• The collapse happened about 270m from the entrance of the Silkyara side.

• The tunnel is a part of the Char Dham all-weather road project which commenced in 2016.

• This has prompted the authorities to launch a mega search and rescue operation.

Possible reasons for the collapse of the tunnel

• Loose patch of rock: It could have happened due to a loose patch of rock, which wasn’t visible during the construction.

• The patch might have consisted of fractured or fragile rock with a lot of joints that may have made it weak.

• Water seepage: Water could have entered through loose patch, eroding the loose rock over time creating a void on the top of the tunnel, which can’t be seen.

• Shear zone: It is created when there is movement between two rocks and the rock gets crushed.

• This crushed rock can change its behaviour, it may have clay, or it may get weathered over time.

The rescue operations

Agencies involved

• The National Disaster Response Force (NDRF), the State Disaster Relief Force (SDRF) and the police are among the main figures in the multi-agency rescue operations.

Current situation

• As per the officials, the labourers are safe, and are being provided with food, water and oxygen.

• The people trapped were contacted through walkie-talkies, through which it was learned that all of those trapped were unharmed.

• As per their request, food was provided through a compression pipe. The distance to reach those trapped is approximately 60 meters.

Under-Construction Uttarakhand Tunnel Collapsed 

• The tunnel is located on the Yamunotri National Highway near Silkyara and was being constructed under the Chardham Highway Project.

• Accident spot located near Main Central Thrust of the Himalayas and this area is extremely sensitive to earthquakes and frictional shear rocks are present in this area.

Experts raised questions on geological and geotechnical surveys for the project and said that mainly two types of incidents occur during tunnel construction in Uttarakhand — 

• Sudden release of large amounts of water and 

• Unexpected encounter of sheared rocks (worn by rubbing against each other).

Silkyara Bend-Barkot Tunnel in Uttarakhand

• Silkyara Tunnel: It is around a 4.5 Km long two-lane Bi-Directional tunnel with an escape passage on Dharasu –Yamunotri.

• The double-lane tunnel is pegged as one of the longest tunnels under the Char Dham all-weather road project and aims to reduce the journey from Uttarkashi to Yamunotri Dham by 26 kilometres.

• From the Silkyara side, 2.3km of tunnel has been constructed, while 1.6km of tunneling work has been completed from the Barkot end. Approximately, a 400m stretch of the tunnel is yet to be constructed.

Significance

• This tunnel will provide all-weather connectivity to Yamunotri, encouraging regional socio-economic development, trade, and tourism within the country. 

• It will reduce the travel distance from Dharasu to Yamunotri by about 20 km and travel time by about an hour.

Char Dham Highway Project

• The project aims to enhance road connectivity and ensure the safety and convenience of pilgrims traveling to Uttarakhand’s 4 major shrines viz. Badrinath, Kedarnath, Gangotri, and Yamunotri.

• The project involved widening and upgrading existing roads, constructing new roads, and implementing measures to make the journey smoother and safer. 

What are the challenges in constructing tunnel in Himalayan region?

• Young mountain: Himalayas are still growing due to the collision between the Indian and the Eurasian tectonic plate.

• Geological complexity: They are characterized by a complex combination of rock types, fault lines, and seismic activity.

• Extreme weather variations: Heavy snowfall and freezing temperatures in winter to intense monsoons and landslides during rainy season significantly impact tunnel construction projects.

• High altitude: The challenges include logistical complexities, limited accessibility and increased transportation costs for manpower and construction materials.

• Seismic vulnerability: The Himalayas are situated in a seismically active zone, making earthquake preparedness a top priority during tunnel construction.

Road Ahead

• Guidelines on safety practices in tunnel construction prepared by the International Tunnelling and Underground Space Association say that particular attention should be given “to the means of escape in an emergency situation in contingency planning”.

• Periodic monitoring of the tunnel construction is important.

• Time and resources must be spend on studying the rock before starting the tunnel project.