Within a span of five months, it's for the second time that the work at the strategic Rohtang tunnel has been hit. After unexpected water ingress affected the excavation work, now it's the debris flowing from a cavity beneath the mighty 13,051-foot Rohtang Pass that has thrown another geological challenge for the engineers.
The excavation work on the south portal of the tunnel at Dhundhi, 27 kilometres uphill the tourist town Manali, has come to a grinding halt. "There has been debris flowing from the cavity in the mountains. The work's progress has been hit adversely," chief engineer, Rohtang tunnel, HS Sharma told Hindustan Times over telephone from Dhundhi.
So far, the workers at Rohtang tunnel have been able to clear 10,000 cubic metres of debris. Engineers are hopeful that the excavation work on the north portal would resume by next week.
"By next week, we shall be able to resume the work," says Sharma. "Right now, we are not able to bore even a meter of rock," he added.
With engineers spending much of their time and energy in plugging the water ingress, there is a growing fear that there could be more geological challenge. "We expect that there will be difficulty in boring the tunnel for another 700 meters," says Sharma, adding, "There is a possibility of the more water ingress in the tunnel."
Continuous flow of water has already slowed down the excavation work at the tunnel. Engineers have undertaken chemical grouting and using polyurethane procured from Switzerland to strengthen the rocks inside the tunnel. Apart from this, rock-bolting and pipe umbrella-roofing are being used to stabiles the overhead rock.
What's adding more difficulty for the workforce at the tunnel is the intermittent snowfall and subzero temperature. The temperature at Dhundhi drops to -20 in December and January.
The work on the north portal at Sisu has been stopped following the official closure of Rohtang Pass for vehicles. Rohtang Pass remains under snow cover for almost a six months a year.
"The work at north portal has been stopped since the Rohtang Pass has been official declared closed for vehicles," says Sharma. The work at north portal will resume only in May after the Border Road Organisation (BRO) undertakes massive snow-clearing exercise. About 1,300 meters of the tunnel has already been bored in the north portal which is approachable from Leh.
Anticipating that the rock strata inside the tunnel could throw more challenges, the BRO has already imported hi-tech and automated equipment, few of them are being used for the first time in the country. Instead of manually-operated boomers, an Austrian company is now using computerised boomers. The project is scheduled to be completed in 2015. The project was inaugurated in June 2010.
The idea of cutting a tunnel across Rohtang Pass was conceived in 1983. The Rs 1,700-crore project is aimed at providing an all-weather route to Lahaul and Spiti in Himachal Pradesh and Ladakh in Jammu and Kashmir. The horse shoe-shaped 8.8-km tunnel will reduce the distance by 46 kilometres.
The importance of having the tunnel was greatly felt during the Kargil conflict in 1999 when the Srinagar-Leh highway came under attack from the Pakistani intruders. During the conflict, all the supplies to the war zone were done through the Manali-Leh highway. The tunnel will reduce the road distance by 46 km and travel time by about three hours when it is completed by 2015.