Rohtang Pass Tunnel Case Study — Geotechnical Monitoring & Instrumentation

Rohtang Pass, now known as Atal Tunnel, is a very famous and popular mountain pass, almost 13,058 ft, situated on the eastern Pir Panjal Range of the Himalayas around 51 km from Manali. Especially known for its mesmerizing landscape, the pass connects the Kullu Valley with the Lahaul and Spiti Valleys of Himachal Pradesh, India.

Known for its scenic beauty, Rohtang Pass holds strategic importance for India. Every year, during July to September, the road becomes a passage to the people of Lahul valley transporting their cash crop, potatoes and peas to the markets across Atal Tunnel to Kullu and earning money for the unstable weather period of 9 months.

The construction of the tunnel was very much awaited and was finally inaugurated on Oct 3rd 2020 by India´s Prime Minister Narendra Modi.

Now that we have introduced the Rohtang Atal Tunnel, let’s see Encardio-rite’s project overview, the instrument used, and the services provided.

Project Overview:

Recognized as one of the highest trafficable passes in the world, the Rohtang pass is designed to create an all-weather route to Leh and Lahaul and Spiti valleys in Himachal Pradesh. The Rohtang Pass Highway Tunnel is situated in the Western Himalaya region of Northern India with its altitude of 3,980 m. With a length of 9.02km, it is also the longest tunnel in the world at an altitude of over 3,000 metres or 10,000 feet above mean sea level.

For about four months, the pass is covered with white sheets of heaviest snowfall and blizzards, making the route inaccessible for anyone.

Renamed after the former Prime Minister of India, Mr. Atal Bihari Vajpayee, the tunnel reduces the travel distance from 4 to 6 hours to only 30 minutes. It also reduces the distance between Manali and Keylong by about 46 km (28.6 mi).

The Rohtang Atal Highway Tunnel with its 8.8km of length is the longest road tunnel in India situated at a high altitude. Apart from high altitude and uncooperative climate, the geological condition in the Himalaya was a big challenge faced by the Encardio Team. Braving the freezing weather, snowfall, frequent floods and thin air, the team soldiered forward, providing with the most accurate sensors and instrumentations.

The rocks found within the tunnel area are mainly schist and migmatite with expected disturbed zones and in some individual areas, high squeezing rock was also found.

Rohtang Pass Tunnel Details:

Shape (cross-section) of the tunnel: Horseshoe

• Finished width: 10.00 m (32.8 ft) at road level.
• Construction technique: Drill & Blast with NATM.
• Overburden: Maximum 1,900 m, average more than 600 m.
• Emergency tunnel: A 2.25 m high and 3.6 m wide emergency tunnel is integrated into the tunnel cross-section beneath the main carriageway. There are 18 egress tunnels, with an opening after every 500 metres in case of any hazard or emergency.
• Other safety measures include telephone connections at every 150 metres for emergency communication, fire hydrant mechanisms at every 60 metres, auto incident detection system with CCTV cameras at every 250 metres, air quality monitoring at every one Km, evacuation lighting/exit signs and broadcasting system throughout the tunnel among others.
• The Atal Rohtang Tunnel will be able to take a traffic of 3000 cars or 1,500 trucks per day, capping the speed limit at 80 km/hr. It also has the state of the art electromechanical system including a semi-transverse ventilation system.
• There are pollution sensors in the tunnel that monitor the air quality in the tunnel. If the quality is below the recommended level, fresh air is injected into the tunnel with the help of two heavy duty fans on each side of the tunnel.

Monitoring Services for Rohtang Pass Tunnel

Encardio-rite was awarded the subcontract for the complete monitoring solutions for the tunnelling work. Let’s have a look at its monitoring solutions.

Being an expert and experienced in geotechnical monitoring, Encardio-rite provided world-class monitoring services during tunnelling. Apart from that, their team also made sure that they were one step ahead of any mishap by continuously conducting geophysical prediction by Tunnel.

Seismic Prediction System (TSP) before tunnelling which recognizes any early signs of fault or fracture zones, or zones where the rock mass characteristic changed. A geological prognosis could be given that enabled the tunnel site management to determine necessary forthcoming tunnelling measures.

Apart from that, a number of turnkey services were provided which are listed below …[Continue reading]