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Saturday , 25 June 2022

High-altitude infrastructure construction

A case of the world’s highest road through Umling La Pass

At 19,300 ft, Umling La is literally perched on top of the world. Constructing a road there could pose unimaginable challenges.

Man and machine working in tandem to blacktop the world’s highest motorable road in Eastern Ladakh at 19,024 ft.

As India celebrated 75 years of independence on 15 August 2021, the Border Roads Organisation (BRO) hoisted the national flag on Umling La Pass in Ladakh, at an altitude of 19,024 ft. This ‘highest motorable Pass’ lies just 15 km from the Line of Actual Control. It is located between Chisumle and Demchok villages in the beautiful Indus Valley. BRO constructed the 52-km long tarmac road through Umling La Pass, setting a record better than a road in Bolivia connecting to its volcano Uturuncu at 18,953 ft. To put things in perspective, this road has been constructed at an altitude higher than both the base camps for Mt Everest. The South Base Camp in Nepal is located at an altitude of 17,598 ft while the North Base Camp in Tibet is at 16,900 ft. The road is also much above the altitude of Siachen glacier, which is at 17,700 ft.

Umling La has a harsh climate, with 60% less oxygen than normal and extremely low temperatures of -40 ºC. This potent combination made constructing the road very difficult as machines and equipment were seriously derated, and human ability severely compromised. This took a toll on BRO workers, who suffered from bouts of nose bleed, dizziness, high blood pressure, and breathing difficulty.

Lining of Sela main tunnel and Nechiphu tunnels in progress on the Balipara-Charduar-Tawang road in Arunachal Pradesh.

The Chisumle–Demchok road takes off from Chisumle on Koyul-Photile-Chisumle-Zursar road, snaking across the hills astride the Umling Nala and ascending continuously for 24 km before it plateaus out for about one km to reach Umling La. From there on, the road descends steeply into the Indus Valley plains at Umlung Zing, through various hairpin bends for 16 km. Thereafter, the road runs along the Indus River for another 12 km, before it terminates at Demchok village.

The high altitude and prevalent climate in Chisumle–Umling La–Demchok restrict construction activities in the period May to September. In order to ensure that the road remains firm and retains its smooth driveability throughout its design life, it had to be ensured that the pavement is free from heaving and thawing effects. Accordingly, the chosen layer composition was non-frost susceptible sub base (NFSSB), with larger particles and no sand, rather than the conventional granular sub base, which is normally used at lower altitudes. This has prevented uneven settlements on the Chisumle–Demchok road due to frost heaving and freeze thawing.

All the four layers of road construction—non-frost susceptible sub base, crushed stone base, dense bituminous macadam and bituminous concrete—lie completely above 18,000 feet. This construction had to be undertaken in a short five-month period, necessitating the deployment of a large amount of resources and manpower. Being a single-lane road, with no alternate roads/tracks available, the deployment of resources itself became a challenge.

The challenge was further accentuated by the hard rock strata. The flexible pavements were constructed under adverse weather conditions within limited time frames, forcing BRO to use the latest and practical methods to minimise the detrimental effects of extreme cold on the road. The effects of adverse weather on BRO personnel were obviated by a smart rotation, wherein everybody worked two days at 18,000 ft followed by one day rest at 15,000 ft. The heavy equipment were maintained by experts, keeping the vehicles on road during the brief working season.

Today, the road is emerging as a tourism hot spot. As traffic flow increases, the road will lead to socio-economic development of the region. From an industry perspective, it can become a test bed location for validating numerous traffic management, road construction and maintenance-related practices.

Paving of roads using M50 grade concrete blocks at Sela top (13680 ft).

Construction in high altitudes using new technologies

Since its inception in 1960, BRO has focused on infrastructure development in border areas, especially in the high-altitude terrain of the Himalayas. Accordingly, it has progressively acquired niche road construction capabilities. Some of the key high-altitude infrastructure projects executed by BRO, in the recent past, are the Umling La Pass at 19,024 ft and the Atal tunnel at 10,500 ft. Another high-altitude under-construction project is the strategically-important Sela and Nechiphu tunnels in Arunachal Pradesh. Once completed, the Sela tunnel will be the longest twin tunnel to have been constructed above 13,000 ft.

The most significant challenge in infrastructure development in these areas relates to the execution of civil engineering construction works. Restricted and frequently-interrupted working seasons, limited availability of skilled manpower in remote locations, challenging weather and terrain conditions, coupled with a significant diurnal variation in temperature, make the execution of both cementitious and bituminous works even more challenging. Some of the innovative and new techniques utilized by BRO to overcome these challenges are described below.

1400 ft Col Chewang Rinchin extra wide Bailey bridge constructed using micro-piling technology by BRO at 14,650 ft.

Non-frost susceptible sub base technique

The construction of the 52-km road through Umling La Pass at 19,024 ft, connecting the villages of Demchok and Chisumle in Ladakh, made use of the non-frost susceptible sub base technique. The pavement was designed to withstand the effects of heaving and thawing while ensuring that the road retains strength and has a good riding surface throughout its design life.

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