When a country like India that is constantly transitioning from developing to a developed belt, there are a lot of infrastructural developments that happen in the background. One such engineering marvel, Rohtang Tunnel is a highway tunnel being built under the Rohtang Pass in the eastern Pir Panjal Range of the Himalayas on the Leh-Manali Highway. This is the world’s longest road tunnel at an altitude of more than 3,000 metres above sea level. This tunnel reduces the distance and commute time between Manali and Keylong by 47 kilometres and 4 hours respectively. This tunnel aims to ensure all-weather connectivity to the landlocked Lahaul valley from the rest of India.
Rohtang tunnel is one of the most important infrastructure projects, which was initiated in 2010 and inaugurated on 3rd Oct 2020. ACC delivered more than 1,60,000 metric tonnes of cement, which was used for different grades of concrete mix, ranging from M-25, M-30, M-40 to M-50 grade concrete. Beyond this, it was used for different applications like the inside lining of the tunnel, rigid concrete pavement, grouting and other allied works. The precast elements were also casted with ACC cement.
Challenges and Solution
Resolving challenges in the constructional journey paves way for a better foundation. The construction team faced a few challenges, but they surely came with benefits. The most challenging task was to continue the excavation process during extreme snow conditions. One-third of the entire tunnel was excavated from the north end, and two-third was excavated from the south end. The progress on the northern end of the tunnel was highly dependent on how negotiable the pass was. As a result, work on the northern end was discontinued during winters (from November to May), and work on the tunnel could be continued only for 10 months from the southern portal.
Rohtang pass is the bottleneck due to heavy snowfall in the region, which made it impossible to drive. However, completion of the tunnel serves as a solution to this problem and ensures all-weather connectivity. With an efficient team and our timely supply support, the entire 475 kilometres long Manali-Keylong-Leh highway, is now motorable round the year. It’s not easy to build a tunnel through the Himalayas. Located 3,000 meters above sea level, the nine-kilometre tunnel that’s part of the Rohtang Tunnel Project is the longest in the world at this altitude. The working conditions were tough, Team ACC performed reliably and safely, navigating through snowfall and avalanches, to ensure cement availability for the construction work, even when roads were washed away.
#Better Building Practices
Extreme low temperature can significantly slow down the hydration of concrete impacting its strength. Here are some recommended precautions to be applied while preparing concrete in cold weather.
- Store the cement in warm and dry storage conditions.
- Ensure heated water is used for concrete mixing. Concrete should be kept warm, at around 10°C, to cure properly. Prior to preparing the concrete, it is recommended to preheat aggregates and sand.
- Ensure heaters are used for keeping accelerators and other admixtures at specified storage temperature. Avoid freezing of liquid chemical admixtures, store them in heated environment to maintain specified storage temperature.
- Avoid pouring concrete over frozen ground. Use heaters to thaw the ground before pouring concrete.
- Maintain a low slump, and minimal water to cement ratio, to reduce bleeding and decrease setting time. Wait until all bleed water has evaporated before finishing.
- To prevent freezing of concrete and to maintain the concrete at an optimal curing temperature use insulated formwork or blankets.