Chenani Nashri tunnel, also known as Patnitop Tunnel, is a road tunnel in the state of Jammu and Kashmir on NH44. The work had started in 2011 and was inaugurated by Prime Minister Narendra Modi on 2 April, 2017. It is Asia’s longest road tunnel. Built at Rs 3720 crore, the tunnel will reduce the distance between Jammu and Kashmir to Srinagar from 41 km to just 10.9 km, potentially saving 99 crores of rupees per year, and a staggering 27 lakhs of fuel money per month. At 50km/hr speed, the tunnel is a 12-15 min drive, cutting travel time by 2 hrs.
The Chenani Nashri tunnel is located on the lower Himalayan range at an altitude of 1200m. It has been excavated starting from about 2km from Chenani town, south of Patnitop to Nashri village, north of Patnitop. The construction involved nearly 1500 engineers, geologists and labourers, besides skilled workers.
The Chenani-Nashri tunnel comprises two tubes that run parallel to each other — the main traffic tunnel of diameter 13 m, and a separate safety or escape tunnel of diameter 6 m alongside. The two tubes — each approximately 9 km long — are connected by 29 cross passages at regular intervals of every 300 meters along the entire length of the tunnel.
These passages add up to about 1 km of tunnel length, and the main and escape tubes, plus the cross passages make up about 19 km of the length. Since such a long tunnel could present the problem of a lack of oxygen, to ensure that there is no excessive carbon-dioxide build up inside, there are several exhaust meters that will check the air all through the length of the tunnel.
With inlets, every 8 meters, bringing fresh air into the main tube, and exhaust outlets every 100 m opening into the escape tube, the tunnel is the country’s first — and the world’s sixth — road tunnel with a transverse ventilation system. Transverse ventilation will keep tailpipe smoke inside the tunnel at a minimum level in order to prevent suffocation and keep visibility at acceptable levels, especially since the tunnel is so long.
The 29 cross passages between the two tunnels will be used to evacuate, through the escape tunnel, a user who might be in distress, or to tow away any vehicle that might have broken down in the main tunnel. A total of 124 cameras and a linear heat detection system inside the tunnel will alert the Integrated Tunnel Control Room (ITCR) located outside the tunnel to the need for intervention. In case of traffic violation, the Control Room will inform the traffic police deployed outside the tunnel, who will fine the errant drivers on the spot.
SOS boxes installed every 150 m will act as emergency hotlines for commuters in distress. To connect to the ITCR to seek help, one would only need to open the door of the SOS box and say ‘Hello’, said the IL&FS (Infrastructure Leasing & Financial Services Ltd) Project Director J S Rathore. Commuters can use their mobile phones inside the tunnel. To prevent diminution of vision as a result of change in the light while going in or coming out of the tunnel, the lighting inside has been adjusted at a gradient of luminous strength.
The Chenani Nashri tunnel is built with fire safety measures. As soon as sensors detect fire, a safety protocol will kick in, and the pushing of fresh air will stop and only exhausts will function. Longitudinal exhaust fans installed at regular intervals will concentrate on 300 m on either side of the fire, pushing the smoke upward. Ambulances or vehicles carrying foam will rush through the escape tunnel to evacuate commuters and fight the fire.
The heat detection system inside will record rises in temperature in the tunnel — the result of excessive emissions which may be caused by one or more vehicles. In such cases, the ITCR will get in touch with staff inside the tunnel, and the offending vehicle will be pulled over into a lay-by and subsequently removed by a crane through the parallel escape tunnel.
Despite having been excavated in difficult geographic conditions, both tubes are completely waterproof.
The Chenani Nashri tunnel will also bypass 44 avalanche and landslide-prone spots on the highway. It is an all-weather tunnel and is said to enable an increase in trade and tourism in the state. Deputy commissioner of Ramban, Aijaz Asad said, “This state-of-the-art tunnel will also have parking spots in case of vehicle break-downs”.