Updated: March 30, 2017 8:19:41 am
The 9.2 km-long road tunnel that bores through the belly of the lower Himalayas between Chenani in Udhampur district and Nashri in Ramban district is an achievement of engineering that incorporates India’s first fully integrated mechanism to externally control everything from the movement of vehicles to the inflow and outflow of air, and even the evacuation of passengers or vehicles in distress.
The tunnel, built at the cost of Rs 3,720 crore in a record time of 5 and a half years by Infrastructure Leasing & Financial Services (IL&FS) Ltd, is located at an altitude of 1,200 metres (nearly 4,000 feet) in difficult Himalayan terrain. It will reduce the travel time on National Highway 44 between Jammu and Srinagar by about 2 hours by shortening the distance between the cities by 30 km, and will altogether bypass Kud, Patnitop and Batote, locations where the highway is prone to being blocked by snow and landslides.
The 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 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 tunnel length.
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With inlets every 8 m bringing fresh air into the main tube, and exhaust outlets every 100 m opening into the escape tube, the Chenani-Nashri tunnel is the country’s first — and the world’s sixth — road tunnel with a transverse ventilation system, IL&FS Project Director J S Rathore said. Fresh air coming into the main tube will push vehicle exhaust upwards and into the other tube; exhaust fans in the parallel escape tunnel too will suck stale air from the main tube and throw it outside, Rathore explained.
Transverse ventilation will keep tailpipe smoke inside the tunnel at a minimum level — this is important, Rathore said, 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.
The heat detection system, Rathore explained, will record rises in temperature in the tunnel — the result, perhaps, of excessive emissions from 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.
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’, Rathore said. The SOS boxes are also equipped with first-aid facility and some essential medicines. In case of breathlessness, claustrophobia or other discomfort, or in case of breakdown of a vehicle, the commuter will be expected to inform the ITCR the number of the nearest crossway, and an ambulance or crane will be rushed through the parallel escape tunnel, Rathore said.
Commuters will also be able to use their mobile phones inside the tunnel. BSNL, Airtel and Idea have set up facilities inside the tunnel to carry signals. 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. Fire safety is an overriding concern, Rathore said. 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.
Despite having been excavated in a difficult Himalayan region, both tubes are 100% waterproof. There will be no seepage of water from the ceilings or any of the walls of the tunnels, Rathore said.
OTHER KEY TUNNELS in J&K
JAWAHAR TUNNEL: Named after India’s Pandit Jawaharlal Nehru, the 2.85 km long tunnel connecting Banihal in Jammu with Qazigund in the Valley was built at an elevation of 2,194 m by two Germans, Alfred Kunz and C Barsel. Work began in 1954; tunnel was opened in December 1956. The Border Roads Organisation renovated it in 1960, giving it a 2-way ventilation system, pollution and temperature sensors, lighting system and emergency phones. While designed for the passage of 150 vehicles on each side daily, the tunnel now sees traffic of nearly 7,000 vehicles every day.
NANDNI TUNNELS: 4 tunnels constructed at a cost of Rs 101.31 crore beneath the Nandni wildlife sanctuary, of lengths between 210 m and 540 m, adding up to a combined length of 1.4 km. They bypass several kilometres of twisty roads, reduce Jammu-Udhampur travel time by more than 30 minutes.
BANIHAL-QAZIGUND: 11.215 km tunnel is India’s longest and Asia’s 4th longest railway tunnel. At an elevation of 1,760 m, the tunnel is 8.4 m wide and 7.39 m in height, and passes under the Jawahar tunnel. The tunnel brings Qazigund and Banihal closer by 17 km — the road distance between the towns is 35 km.
UDHAMPUR-KATRA: There are 7 tunnels of total 11 km length (the longest is 3.15 km) on this 25 km stretch of railway line built at a cost of Rs 1,132 crore.
JAMMU-UDHAMPUR: There are 20 tunnels (the longest being 2.5 km) on this 53 km stretch of railway tracks.
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