Manali. Prime Minister Narendra Modi in October 3 inaugurated the world’s longest 9km mountain tunnel through the Himalayas, all-weather Atal Tunnel connecting the Northern Indian state of Himachal Pradesh with the centrally administered Ladakh region, cutting travel time for civilian and military traffic by four hours.
“Atal tunnel will give new strength to India’s border infrastructure. It is an example of world-class border connectivity. There have been demands to improve border infrastructure but for a long time, such projects either couldn’t get out of planning stage or got stuck midway,” Modi said.
At present, the Leh-Manali Highway, is one of only two routes to Ladakh for the movement of civilian traffic and military supplies to the Line of Actual Control (LAC) with China as also the Siachen Glacier but is motorable for only four months a year due to heavy snowfall. The other route is through the Zoji Lah on the Srinagar-Drass-Leh Highway that also gets blocked by snow for nearly four months in a year. Construction of a 14 km long tunnel under Zoji La has also been planned.
At 3,100 metres, the single tube 10-metre-wide double-carriageway Atal Tunnel, incorporates a host of safety features and is expected to daily cater to some 3,000 cars and 1,500 trucks, including transporters of heavy tanks like the T-90. It has been built over a 10 year period at a cost of Rs. 4,000 crore ($300 million).
Vehicular management and checking pollution is a priority. For this, there is a telephone facility at every 150 metres, emergency exits every 500 metres and turning caverns every 2.2 km.
CCTV cameras have been placed every 250 metres and will be connected to two monitoring rooms on both ends of the tunnel. Sensors to check the pollution level will keep on updating data and if the record is above the desired level, the quantity of fresh air injected inside the tunnel – through two heavy duty fans each on both openings – would be increased. Pollution level will be controlled within 90 seconds.
The tunnel has a semi-transverse ventilation system, where large fans would separately circulate air throughout the tunnel length. Another safety feature is that if a fire were to erupt inside the tunnel, it will be controlled within an area of 200 metres and fire hydrants will be provided on specific locations.
The tunnel also has a public announcement system to make important announcements in emergency situations for which loudspeakers have been installed at regular distances.
The latest Austrian tunnelling method and ventilation system – semi transverse type considered as safest – has been adopted for the project. Heavy snowfall in the Rohtang Pass area is a major concern, especially on the approach roads to the tunnel and avalanche-control structures have been constructed to prevent damage to the roads and to ensure the safety of the roads and tunnel users alike.
The most challenging task was to continue the excavation during heavy snowfall in winter. Excavation for tunnelling was done from both ends. However, as Rohtang Pass closes during the winter, the north portal was not accessible during winter and the excavation was being done only from the south portal in winter. Only about one-fourth of the entire tunnel was excavated from the north end and three-fourths from the south end. There were more than 46 avalanche sites on approaches to the tunnel.
Other challenges to the progress of the tunnel included difficulties in disposing more than 800,000 m³ of excavated rock and soil, heavy ingress of water (as much as 3 million litres per day in June 2012) that required constant dewatering, costlier treatment and slowed the progress of excavation from 5-metre per day to just half a metre a day and unstable rocks that slowed blasting and digging. A cloud-burst and flash flood on August 8 2003 killed 42 labourers who were building the temporary access road. Questions were also raised on the impact of cutting down more than 700 trees on the ecology but these were found to outweigh the benefits of the tunnel.
On November 22, 2017, patients were allowed to be carried through the under-construction tunnel only in the gravest of emergency when the helicopter service was not available and not to allow civilians to enter the tunnel before completion due to risks of falling rocks, lack of oxygen in the tunnel as ventilation system was yet to be installed and likely interruption in construction work due to presence of civilians.
The trial run of a bus service started through the yet-incomplete tunnel on November 17, 2019. A Himachal Road Transport Corporation bus carrying 44 passengers entered tunnel from the south portal and the passengers alighted at the north portal. The bus ran once a day over the next five winter months till the Rohtang Pass opened.
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