The Border Roads Organisation (BRO) has been executing tunnel projects in some of the most difficult terrains of the country. Despite dealing with challenges such as extreme temperatures and difficult geographic conditions, the organisation has successfully completed four tunnel projects in India including Atal Tunnel, Sonapur Tunnel, Theng Tunnel and Chamba Tunnel. At a recent India Infrastructure conference, Lt. General Rajeev Chaudhary, VSM, Director General, Border Roads, discussed the ongoing progress of BRO’s tunnelling projects, the construction challenges, the measures to mitigate challenges and the key lessons learnt. Excerpts…
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The BRO is a premier road construction executive force which provides support to, and is an integral part of the Indian Armed Forces under the MoD. It is predominatly involved in development of road infrastructure in border regions of the country which not only enhances the operational capability of our Armed Forces but also provides last mile connectivity by integrating our untouched border villages with the heartland. BRO has its presence in 11 states and three union territories (including Andaman & Nicobar Islands) and friendly foreign countries such as Bhutan. Over a span of 63 years, BRO has constructed more than 60,000 km of roads and is currently maintaining about 23,000 km of roads, of which 15,000 km of roads are under maintenance and 8,000 km of roads are being upgraded. A further 14,000 km of roads under construction while about 3,000 km are under planning. Of the 13 highest roads in the world, 10 have been constructed and are being maintained by BRO at present. The budgetary allocations for BRO have surged, especially in the last two to three years. In 2022-23, it stands at Rs 135 billion, up from Rs 93.75 billion in 2021-22 and Rs 87.63 billion in 2020-21. In 2023-24, the Ministry of Finance approved an allocation of Rs 50 billion against the capital head, which is a twofold increase from the budget estimate (BE) for 2021-22. This is an unprecedented jump of 100 per cent within a span of two years, which is a reward for good work done by BRO.
“Of the 13 highest roads in the world, 10 have been constructed and are being maintained by BRO.”
BRO has undertaken a fourfold process to train key personnel so as to enhance their expertise in tunnel project execution. Selected engineers are sent abroad for tunnel-specific courses, after which they conduct in-house training to train the staff. In addition to this, site visits to completed projects are also conducted so as to provide hands-on knowledge regarding the complexities of executing tunnel projects in harsh conditions.
So far, BRO has completed four tunnel projects that include Atal Tunnel in Rohtang in 2020. It is a 9.02 Km-long tunnel and is recognised as the world’s longest highway tunnel, at an altitude above 10,000 feet. It is a single-tube, double-lane, horseshoe-type tunnel with a design speed of 80 km per hour. Last year, BRO has also constructed Chamba Tunnel, which is 440 m long and has been constructed under the town on Rishikesh- Dharasu road in Uttarakhand. It entailed an investment of Rs 0.88 billion. It is a horse shoe-shaped tunnel. The completion of this tunnel has helped increase connectivity to far-off places in the Garhwal region of Uttarakhand. Apart from this, BRO has completed the construction of the 578 m-long Theng Tunnel on the Chungthang-Mangan highway in North Sikkim. This bi-directional tunnel is the longest in Sikkim. It has improved connectivity to the border regions. Similarly, the 120 m-long cut-and-cover Sonapur Tunnel in Meghalaya has improved movement by enabling all-weather connectivity between Meghalaya and the Barak Valley District in Assam.
At present, BRO is constructing 11 tunnels in the State of Arunachal Pradesh, Sikkim and UT of Jammu & Kashmir and of Ladakh. These 11 ongoing tunnels are Sungal Tunnel (2,790 m), Naushera Tunnel (700 m), Bhimber Gali Tunnel (1,100 m), Kandi Tunnel (260 m), Tunnel on DS DBO Road (920 m), Sela Tunnel (2,535 m), Nechiphu Tunnel (500 m) and, Tunnel on the Sela-Chabrella feeder road (105 m), two cut and cover tunnels of length 170 m and 60 m on the Tahiha-Nacho Road and one tunnel of length 140 m on the Hapori-Sarli-Huri Road. Furthermore, some of the upcoming tunnels in the pipeline are the Hamboting La Tunnel (2,200 m), Key La Tunnel (8,200 m), Shinku La Tunnel (4,100 m), Tangla La Tunnel (1,500 m), Lachung La Tunnel (15,260 m), Baralacha La Tunnel (13800 m), Donkya La Tunnel (1,400 m), and the Brahmaputra Under Water Tunnel (9,800 m).
Apart for this, two tunnels on the Namik La and Fotu La passes of length 2.50 km and 1.70 km respectively on the Zozila-Kargil-Leh Road are also under active consideration under the Ladakh Development Package through their funding.
Construction challenges and remedies
BRO has faced many challenges in the execution of tunnel works because of the location and the geographic complexities of the projects undertaken by the organisation. The key challenges include limited and risky working spaces, complex and unknown geographical conditions, areas prone to frequent landslides, steep slopes with unstable strata, and the constant risk of calamities. Apart from this, a pertinent challenge faced in tunnelling in these geographies is the supply of material and equipment. Owing to the rugged and difficult terrain, it is extremely difficult to induct the equipment to the project location.
Another big challenge faced is the lack of trained manpower. Further, out of the organisation’s 31,000-strong work force, nearly 88 per cent are deployed at higher altitude areas every three to four years, thereby affecting their health. The temperature reaches as low as -40°Celsius. Working under such harsh conditions, the organisation has nearly 250 causalities on a yearly basis.
“Over a span of 63 years, BRO has constructed more than 60,000 km of roads and is currently maintaining about 23,000 km.”
During the course of execution of Atal Tunnel, the most difficult challenge was the Seri Nala Fault Zone, encountered between chainage 1,887 and chainage 2,474.5. A shear zone of such length (587.5 m) had never been encountered in a single stretch of any highway tunnelling project in the world before, and took almost four years to overcome. From chainage 1,887 onward, the quality of rock started deteriorating, and at chainage 1,950, the condition at the face became devoid of rock. Muck, along with water, started flowing from the face inside the tunnel due to the weathering caused by Seri Nala, under which the tunnel was passing at that time. Remedial measures undertaken to overcome this challenge included pipe roofing, chemical grouting, pilot tunnelling, micro-piling and waterproofing of membrane. The roof was required to be strengthened to carry out excavation underneath. The strengthening was carried out using large-diameter seamless perforated pipes of long length (12-15 m). An umbrella of pipes was created in the tunnel crown at the required spacing. Externally deployed remedial measures included three different types of treatments/structures by NHPC Limited for diverting Seri Nala’s discharge from its natural course to the South Portal of Atal Tunnel.
The way ahead
BRO is the pioneer in the construction and maintenance of tunnels in some of the most difficult areas across the world and has made persistent efforts in providing all-weather connectivity to the remotest parts of the nation. The tryst with such sustainable connectivity is not yet over and projects such as Shinku La tunnel for connectivity to Leh, Sela and Nechiphu tunnels for connecting Tawang, and an underwater tunnel under the Brahmaputra river are in the offing. The high quality of work in the Atal Tunnel executed by BRO has been recognised, with the tunnel being awarded many prestigious awards. With BRO’s foray into the departmental construction of tunnels, there is no doubt that BRO will emerge as one of the leading agencies worldwide in the field of tunnel construction.