Tunnel construction has become an integral part of infrastructure development in India. It has seen significant growth in the past few years, owing to development across key infrastructure sectors, including urban rail, roads and highways, hydropower, irrigation and water. The introduction of initiatives such as the Pradhan Mantri Krishi Sinchayee Yojana, the Interlinking of Rivers Programme and the Jawaharlal Nehru National Urban Renewal Mission for the exploitation of water resources has given a fillip to tunnel construction for irrigation, water supply and sewerage. Similarly, increasing development in the metro rail sector has spurred tunnelling activity. The roads and highway tunnels are also witnessing a rise, especially in the hilly regions.
Current market size
According to projects tracked by India Infrastructure Research, India has more than 2,500 km of completed tunnel length. A sector-wise analysis indicates that the hydropower sector has the highest share of completed tunnels of over 1,200 km, followed by irrigation (more than 470 km), railways (more than 270 km), metro tunnels (more than 240 km), water and sewerage (more than 230 km) and roads (more than 60 km).
With regard to upcoming tunnels, the tunnelling sector offers a strong pipeline of around 1,300 tunnels, spanning a length of more than 3,600 km. In terms of upcoming (under planning, under bidding and ongoing categories) tunnels, Jammu & Kashmir offers the largest pipeline with around 200 tunnels, followed by Maharashtra (around 140 tunnels), Himachal Pradesh (more than 100 tunnels), Andhra Pradesh (around 90 tunnels) and Arunachal Pradesh (around 80 tunnels). In terms of upcoming length, Maharashtra has the maximum share with over 1,100 km, followed by Jammu & Kashmir with over 460 km and Uttarakhand with more than 280 km.
Construction techniques 
Advancements in tunnel techniques and underground space engineering have played a pivotal role in enabling faster and more efficient construction. According to projects tracked by India Infrastructure Research, more than 200 km of tunnels, in total, are coming up in the future and are deploying the DBM technique in construction. In these projects, the DBM is also being used in combination with other techniques.
The New Austrian Tunnelling Method (NATM) is gaining prominence in the country. NATM is the preferred technique in uncertain geological and hydrogeological conditions. It is now being used in sectors such as railways, metros, roads and highways. A total of over 280 km of tunnels are using the NATM technology for construction in the upcoming tunnels (also includes a combination of techniques used along with NATM). Tunnel boring machines (TBMs) are also gaining traction in tunnel construction, especially in the roads and highway and metro sectors, as these are suitable for tunnel construction in urban areas. TBMs are being used as an alternative to the DBM and other conventional methods. More than 350 km of tunnels are upcoming that are using TBMs for construction, along with other techniques in combination. Micro-tunnelling, also known as trenchless or pipe-jacking technology, is an emerging tunnelling technique in the country. It is being used mostly to lay water supply pipelines and sewers in congested areas. It is used for laying large diameter gravity sewers in cities where open cut installation is difficult, particularly with diameters ranging from 600 mm to 3,000 mm. It is best suited for tunnels under roads with high traffic volumes, railways, rivers, etc.
Modern tunnels
In recent years, contractors have started exploring modern techniques for tunnel construction. These include advanced features such as video surveillance, integrated tunnel control systems, entrance detection control, wireless communication systems, electrical fire signalling systems, SOS call boxes, sequential excavation and ground freezing, among others. Moreover, innovative materials such as fibre bolts, lining stress controllers, geosynthetics and steel anchors are being used in the construction. The Zojila tunnel in India is being developed as a smart tunnel with safety features such as a fully transverse ventilation system, CCTV monitoring, emergency lighting, traffic logging equipment and a tunnel radio system. Many new technologies are also being used in tunnel construction for better geological and geotechnical investigations. Aerial and photogrammetry-based surveys are being conducted and GPS-based systems with high accuracy levels are being adopted for mapping difficult terrain.
New and innovative materials are being used to improve the durability and strength of tunnels. The application of unique and cutting-edge materials has become essential due to the increasing complexity of tunnel construction, especially in the Himalayan and peninsular regions. Tunnel contractors have begun utilising a variety of innovative materials, such as mechanical single bolts, expanding friction bolts, self-drilling rock bolts, steel- and fibre-reinforced polymer active anchors, steel passive anchors, etc., for increased construction efficiency.
Pain points
The tunnelling sector in India continues to face several issues and challenges. Key amongst them are inappropriately designed contract documents and inadequate contracting practices. The contracts are drafted on age-old norms, and leave substantial room for ambiguity in the roles of the implementing agency and contractors. Another challenge faced by tunnelling contractors is the shortage of skilled manpower for handling sophisticated tunnelling equipment. Due to inadequate training, many tunnel construction personnel prefer machinery expertise and are unable to address the obstacles that occur. Other challenges include lack of safety in tunnel construction and maintenance, inadequate investigations, risk management, and undefined methodologies for working out rates for extra items and deviations in the design or construction requirements. These challenges eventually lead to considerable cost and time overruns in tunnel construction projects.
Growth opportunities
Going forward, the overall outlook for tunnel development in the country remains promising. Many new projects are in the pipeline, which are expected to create opportunities for contractors, consultants, and technology and equipment providers. The schemes and programmes of the government such as the Gati Shakti Master Plan are expected to boost the infrastructure capabilities in the country and thereby provide a fillip to the tunnelling sector.
Future tunnel construction projects are anticipated to draw interest from Indian and foreign joint ventures, and more players are expected to enter the market. To ensure on-time and successful completion of projects, it is necessary to address pressing issues including the lack of skilled manpower, contract disputes and delays in land acquisition.
