The tunnelling market is largely dominated by the hydropower, railway, road and highway, metro rail and irrigation, water and sewerage sectors. Large-scale projects have been developed in each of these sectors using innovative technologies. Some key projects along with implementation strategies, issues faced and lessons learnt are discussed below.
One of the first rail tunnels to be built in India dates back to the nineteenth century. Some of the landmark projects in the early years were the Kalka-Shimla line constructed in 1903 and the Konkan rail line completed in 1998. Indian Railways (IR) is currently implementing the biggest railway tunnelling project in the country – the Jammu-Udhampur-Katra-Qazigund-Baramulla rail line in Jammu & Kashmir. It involves the development of a total tunnel length of 123.9 km by 2016-17. Another major project being implemented by IR is the Jiribam-Tupul rail line which involves construction of 35 tunnels. The project is being developed by IR’s subsidiary, North East Frontier Railway, and most of the construction work for this line has been awarded to Hindustan Construction Company Limited.
Railway tunnels are predominantly excavated using drill-and-blast (DBM) heading and benching or classical methods. This is due to the fact that most of the tunnels are constructed in difficult terrain in the Western Ghats, and the northern and north-eastern regions, for which DBM is the most suitable method. More recently, project developers have started to use the semi-mechanised, New Austrian Tunnelling method (NATM) for tunnel construction.
In terms of number of tunnels in the railway sector, Himachal Pradesh has the maximum number at various stages of development – recently completed, under implementation and planning. The state is followed by Maharashtra, Jammu & Kashmir and Uttarakhand. The government’s focus on all-weather connectivity in strategic and sensitive areas is the key driver for a large number of tunnel works in Jammu & Kashmir. The railway tunnelling segment offers a huge pipeline of projects in the planning/preliminary stage with detailed project report (DPR) preparation initiated for a few. The maximum length of tunnels is planned in Jammu & Kashmir and Uttarakhand. Two major upcoming
projects in the region are the Rishikesh-Karanprayag railway line (81 tunnels; 105 km) and the Bilaspur-Mandi-Leh new railway line (360 km).
Roads and highways
Tunnels have been a part of road and highway projects in the country since the 1950s. The highest number of road tunnels has been constructed in the Western Ghats and the Himalayan region. Major project developers involved with tunnels in the road sector are the National Highways Authority of India (NHAI), the Border Roads Organisation (BRO) and state road development entities such as the Maharashtra State Road Development Corporation (MSRDC) and the Himachal Pradesh Public Works Department. Tunnel projects undertaken by the BRO are generally strategic roads in difficult terrain, while national highways and state highways/roads are undertaken by NHAI and state agencies respectively. A state-wise analysis shows that Maharashtra and Jammu & Kashmir have the maximum tunnels in terms of number and length. The longest tunnel currently under implementation is on the Chenani-Nashri section of National Highway 1A in Jammu & Kashmir. The 9 km tunnel is being developed on a build-operate-transfer basis by IL&FS Transportation Networks Limited at an investment of Rs 37.2 billion. The project is expected to be completed by end-2016.
The tunnelling segment in the road sector is likely to get a big push in the coming years with a huge pipeline of projects under the National Highways Development Programme (NHDP) coupled with recent policy initiatives to simplify project implementation and create an investor-friendly environment. The maximum opportunity for tunnel construction is in Jammu & Kashmir, Maharashtra and Karnataka. Tenders for the Zojila pass tunnel project in Jammu & Kashmir, worth Rs 100.5 billion, are expected to be invited soon. The project was initially awarded to IRB Infrastructure; however, the government has decided to rebid the project.
Based on recent trends, the majority of these upcoming tunnels are expected to use the drill-and-blast method or NATM. For hilly areas, NATM will continue to be a preferred method as it is highly adaptable and can be modified according to ground conditions.
Metro rail projects are the most recent entrants in the tunnelling segment. Kolkata metro rail was the first to operationalise an underground system, way back in the 1980s. However, tunnel development in this sector received an impetus from the Delhi metro rail project, which initiated tunnel construction in 2001. Since then, other Tier I cities across the country have launched metro rail projects, with several sections running underground. In terms of length of tunnels, Delhi and Chennai have the longest tunnel network.
Tunnel boring machines (TBMs) are the most commonly used technique in metro rail construction. TBMs were first used for the Delhi metro Phase I project. Subsequently, most of the metro works have been or are being executed using TBMs because of the inherent challenges of construction in urban areas. The use of TBMs minimises disturbance to the surrounding ground and are thus suitable for use in densely populated areas as compared to the traditional cut-and-cover method. At present, all TBMs are designed and supplied by foreign manufacturers. Some of the major suppliers are Herrenknecht (Germany), Hitachi-Zosen (Japan), Okumura (Japan), Robbins (USA), STEC (China), Mitsubishi Heavy Industries (Japan) and Terratec (Australia).
Tunnel construction is expected to pick up pace in the next five years, as Tier II cities initiate their metro projects. Growing urbanisation and the need for an integrated transport system are the two biggest drivers in the sector.
Irrigation, water supply and sewerage
The irrigation, water supply and sewerage sectors have been among the biggest markets for tunnels in the country and have grown steadily since the 1950s. Among these, irrigation projects have presented the maximum opportunities for the tunnelling industry, followed by urban water supply projects.
State-wise, Maharashtra leads tunnel construction in terms of length and number, followed by Rajasthan and Karnataka. While analysing tunnels with respect to shape, horse-shoe appears to be the most dominant. However, in terms of length of tunnels, the circular shape is foremost. Data also suggests that the horseshoe shape is the most common in irrigation and sewerage tunnels while the circular shape is the most popular for urban water supply tunnels.
Further, with respect to tunnelling methods and techniques, drill-and-blast and TBMs are the most commonly used methods of tunnelling in the sector. Generally, for longer tunnels, TBMs are considered more cost-effective than drill-and-blast or excavation techniques because of their higher advance rates. (The advance rate is the average rate of TBM progress in a specified period of time.)
Growing urbanisation and increasing demand for food will be the two biggest drivers for tunnelling in the irrigation, water supply and sewerage sector. Going forward, interlinking of rivers planned by the central and state governments will present significant opportunities for tunnel development.
The hydropower sector requires the most amount of tunnelling work due to the large tunnel size associated with dam projects. Further, a large fraction of the potential hydropower resources in the country is yet to be tapped. As per the Central Electricity Authority (CEA), about 75 per cent of the hydropower potential is yet to be developed in Jammu & Kashmir, 41 per cent in Himachal Pradesh, 75 per cent in Uttarakhand, and over 90 per cent in the Northeast. Prospective projects in these states, when developed, will present a huge opportunity for tunnelling work. At present, the majority of the tunnel works in the hydropower segment are carried out in the Himalayan geology.
The hydropower sector is likely to receive a big fillip in the coming years given the huge pipeline of projects in the planning stage as well as the recent government initiatives to promote clean energy in the country. A state-wise analysis shows that the maximum number of hydropower tunnels is in Arunachal Pradesh, Himachal Pradesh and Uttarakhand. These tunnels are generally horseshoe or circular in shape, and most of them are excavated using drill-and-blast or conventional methodology.
With 10.8 GW of capacity increment targeted during the Twelfth Five Year Plan (2012-2017) and the increasing focus of the government on reviving stalled projects, private investment is also expected to increase in the sector.
The tunnelling segment has a very large number of projects in the pipeline. However, in the past, issues such as delay in land acquisition, financial crunch, and termination of contract due to lack of coordination between parties involved in the project have hampered growth of the sector. For successful implementation of upcoming projects, steps such as greater mobilisation of funds in a decentralised manner and simplification of the land acquisition process need to be urgently taken.