Tunnel development in India has accelerated over the past decade or so. This is driven by increased investments in the hydropower, railway, road and highway, metro rail, and water and sewerage sectors. According to India Infrastructure Research, over 1,600 tunnels spanning over 2,750 km are at different stages of development – completed, under construction and awarded. In terms of length, about 63 per cent of this tunnel length has been completed, 36 per cent is under construction and the remaining 1 per cent has been awarded recently. Sector-wise, hydropower has the maximum length of tunnels (over 1,484 km), followed by railways (over 512 km), irrigation, water supply and sewerage (over 332 km), metro rail (over 202 km) and roads (over 95 km).
In the past few years, India has seen the development of several challenging projects. India’s longest road tunnel, the 9 km landmark Chenani-Nashri tunnel on the Jammu-Srinagar national highway, was operationalised in April 2017. The 8.8 km Rohtang tunnel on the Leh-Manali highway is being built at an altitude of 10,000 feet. The world’s longest tunnel built using tunnel boring machines (TBMs), the 43.5 km Alimineti Madhava Reddy (AMR) project is currently under construction in Andhra Pradesh. Another ongoing project in the state is the Godavari lift irrigation tunnel, Phase III, with a tunnel length of 84.5 km. India’s first underwater 520 metre twin tunnel is also being constructed as a part of the 16.6 km long East-West metro project in Kolkata. While the first underwater tunnel is complete, the second one is expected to be completed soon.
The structure of the tunnelling industry is constantly evolving, with the entry of new domestic and foreign players. Domestic players are entering into tie-ups and strategic alliances with global players to bring in the latest technology and equipment. On the global front too, consolidation and business expansion has been a key feature of the tunnelling industry.
New designs, technologies and construction techniques for tunnelling are becoming a growing area of interest for the industry. Advanced mechanised techniques such as the use of TBMs and the New Austrian Tunnelling Method (NATM) are gaining prominence with increased tunnelling activity in congested urban spaces, primarily for metro rail and urban water supply projects. Typically, these mechanised techniques involve higher equipment and transportation costs in comparison to conventional methods like drill-and-blast and cut-and-cover. However, they have higher advanced rates (the average rate of TBM progress in a specified period of time), and hence save construction time. Also, traffic disruptions, quantity of debris and associated environmental impacts are much less when mechanised methods are used.
For the construction of water supply and sewerage tunnels, a variety of new trenchless technologies such as micro-tunnelling and horizontal directional drilling are being deployed. Further, special techniques and methods such as the DRESS (drainage, reinforcement, excavation, support and solution) are increasingly being considered as a viable solution for tunnelling in challenging rock and soil conditions. There is also an increased emphasis on pre-excavation investigation and surveys.
Overall, the conventional drill-and-blast method of tunnelling continues to remain the most widely used technique for the development of tunnels. The technique is primarily being used in the hydropower, road and railway sectors, where tunnels are mostly built in the Himalayan region and the Western Ghats.
Further, the standards of tunnel design and engineering are continuously improving. New types of materials are also being used to improve the durability and strength of tunnels. For instance, steel fibre-reinforced concrete and micro silica or micro fine cement are being used for improving tunnel strength. Artificial ground freezing is being used for soft ground tunnelling to create a watertight barrier as a support system. Recently, tunnel contractors have started using a metakolin mineral admixture for high strength concrete and grouting. Self-compacting concrete has also emerged as a cost-effective option for casting heavily reinforced elements and complex geometrical shapes.
The tunnelling equipment market is also witnessing strong growth. The scope of work for equipment suppliers has evolved and expanded over the years. Apart from supplying equipment, companies also provide services such as total logistics support, on-site first-time assembly, technical assistance, specialised manpower for the maintenance of TBMs and on-site excavation services as requested by the client. Renting equipment from bigger players has also emerged as a preferred option.
Moreover, tunnel contractors are exploring new markets to acquire/import new tunnelling equipment and machinery. Singapore, China, Germany and Finland have emerged as the top four tunnel machinery exporting countries.
Outlook
Going forward, the outlook for the tunnel development market is promising and will be driven by the central government’s focus on infrastructure development. One of the major growth drivers for tunnel construction will be the urban rail segment. About 2,050 km of metro rail network is expected to be added in the next six to eight years. Further, large investments are planned for the construction of all-weather roads and new tunnels in strategic and sensitive areas. The Indian Railways’ capex target for 2017-18 is an all-time high of Rs 1.3 trillion. Hydropower capacity is also expected to increase by 13 GW in the next five to six years. These capacity addition targets augur well for the tunnelling industry.
According to India Infrastructure Research, around 4,000 km of tunnel length is either under construction or is planned to be taken up in the future. Projects involving longer tunnels are being planned and proposed across different infrastructure sectors. Maharashtra has a few proposed projects with unprecedented lengths. The Mumbai tunnel ring road project is expected to have a tunnel length of 34 km, while the Mumbai metro rail project Line 3 is completely underground with a network of 34 km. Line 2 and Line 4 are also being planned, with tunnel lengths of 40 km and 27 km respectively.
In Rajasthan, two tunnels spanning 290 km are being proposed under the Mahi-Luni intra-state link project. Further, the Andhra Pradesh government is planning a 3 km long underwater tunnel for vehicular traffic under the Krishna river in its capital city of Amaravati.
The tunnelling segment is thus expected to offer significant business opportunities for contractors, technology providers, and equipment and material suppliers. However, issues such as geological complexities, inadequate investigations, deficiencies in contract documents, complexities of the Himalayan region and the Western Ghats, and safety risks need to be urgently addressed to enhance productivity and ensure timely project execution.
