With the increased focus on infrastructure development, tunnel construction in the country has picked up pace in recent years. Tunnels play an important role in setting up hydropower projects, developing urban mass rapid transit systems, improving road and rail connectivity and upgrading water supply and sewerage systems. Large-scale projects with longer tunnels are being taken up using innovative technologies and in some of the world’s most difficult terrain conditions.
Indian Infrastructure reviews the existing project portfolio in the road, hydropower, railway, metro rail, and water supply and sewerage sectors and highlights some big-ticket projects that have been undertaken in the past three to four years…
Road tunnels
In the roads and highways sector, India Infrastructure Research tracked 75 projects across the country. Of these, 55 projects, comprising 64 tunnels with a total length of 246.79 km, are at the planning stage. A state-wise analysis indicates that in terms of length, Jammu & Kashmir has the maximum share of total completed, ongoing and awarded tunnel length at 31.92 km. This is followed by Maharashtra with tunnels spanning a length of 29.03 km and Himachal Pradesh with 20.45 km. The most commonly used technology for tunnel construction in the sector is the drill and blast method (DBM). However, the New Austrian Tunnelling Method (NATM) is now emerging as a preferred option, especially in the Himalayan region that has difficult terrain conditions.
Some of the key completed projects in the sector are the Chenani-Nashri tunnel in Jammu & Kashmir, the Mumbai-Pune Expressway in Maharashtra, and the Aut-Kullu tunnel in Himachal Pradesh. The Chenani-Nashri tunnel constructed between Udhampur and Ramban is the longest tunnel in the country. The 9 km long tunnel is a single-tube bidirectional tunnel, comprising a 9.35 metre carriageway with a vertical clearance of 5 metres and a parallel escape tunnel.
One of the most important projects under implementation at present is the 8.8 km Rohtang tunnel. The horseshoe-shaped tunnel is located at an altitude of over 3,000 metres and is a single-tube, double-lane tunnel that will ensure all-weather connectivity to Lahul Valley from Manali. The project has faced several challenges including poor tunnelling conditions, high ingress of water, low temperatures, varying geology, etc. Of these, a key issue was the high ingress of water from the Seri Nullah leading to frequent disruptions in project execution.
The key upcoming projects in the sector include the tunnels at Lachung La, Tanglang La and Shinkun La in the Ladakh region and the Gurez tunnel project in Bandipora district in Jammu & Kashmir, the Shiradi Ghat tunnel road bypass project in Karnataka and the Amravati-Anantapur Expressway project in Andhra Pradesh. The construction contract for the ambitious Zojila tunnel project has been terminated. The bids for the 14.5 km tunnel that will provide all-weather connectivity between Srinagar, Kargil and Leh are expected to be invited soon.
Development in the sector is expected to be driven by initiatives such as the Bharatmala Pariyojana, Setu Bharatam, Char Dham Connectivity and the development of economic corridors. However, there is a need to resolve issues such as inadequate investigations, unrealistic contractual timelines, land acquisition and inadequate design support to improve tunnel construction.
Hydropower tunnels
Of the 606 hydro projects tracked by India Infrastructure Research, around 505 projects with a length of 1,152.49 km have been completed, 85 projects spanning 286.27 km are under construction and 16 projects with a length of 37.21 km have been awarded. State-wise, Himachal Pradesh has the maximum share of projects with a total tunnel length of 500 km, followed by Uttarakhand with 160.8 km and Jammu & Kashmir with 135.14 km.
In the hydropower sector, DBM is the most commonly used tunnelling method. The deployment of faster and highly advanced/mechanised technologies such as the tunnel boring machines (TBMs) is also increasing slowly. Some of the projects that have used TBMs are the Dulhasti project and the Kishanganga project in Jammu & Kashmir and the Parbati II hydro project in Himachal Pradesh. The NATM technology is also gaining traction.
The country is endowed with a rich hydropower potential. Some of the longest tunnels in the country are in hydro projects. Almost 75 per cent of the total potential for hydropower development is concentrated in the Himalayan regions. However, most of the potential still remains untapped due to the slow pace of development. Tunnelling activity in the Himalayan region poses great challenges due to topographic and geological complexities. Long hydro tunnels have suffered from time and cost overruns due to geological problems such as sheared rock, high ingress of water, high geothermal gradient, emission of noxious gases, etc.
The overall experience with tunnel development in the sector has been mixed. Successes include the Loktak, Chamera I, Uri Stage I, Nathpa Jhakri and Kishanganga hydro projects. The projects that encountered problems and act as eye-openers include the Ranganadi, Dulhasti, Parbati II, Tapovan and Vishnugad projects.
A number of hydro projects such as Kynshi Stage II in Meghalaya, Pakal Dul in Jammu & Kashmir, and Parbati II in Himachal Pradesh are under development. The states of Arunachal Pradesh, Himachal Pradesh and Uttarakhand have the highest share of upcoming hydro projects. Some of these include the Nyamjang Chhu and Upper Siang hydro projects in Arunachal Pradesh, the Gypsa Dam project in Himachal Pradesh and the Devsari hydro project in Uttarakhand.
The sector has seen the emergence of new trends such as the use of steel fibres in shotcrete, self-drilling anchor bolts and adoption of methods such as PU grout, pipe roofing and pre-grouting techniques. However, the sector remains plagued by challenges. The share of hydropower in total power generation has come down from 25 per cent to just 13 per cent. To tap the hydropower potential, there is a need to undertake comprehensive investigations, select the right methodology and agency, and undertake proper identification and management of risks.
Railway tunnels
India Infrastructure Research tracked 84 projects with 1,027 tunnels in the railway sector. In terms of length, a tunnel length of 246.16 km has been completed, 334.44 km is under development and 130.43 km has been recently awarded. Jammu & Kashmir has the highest share in the total completed, ongoing and awarded tunnel length at 182.45 km, while Uttarakhand and Manipur have a tunnel length of 105.48 km and 81.88 km respectively.
Data of a sample of 436 tunnels suggests that DBM is the most commonly used method for the development of railway tunnels, followed by NATM and conventional methods.
One of the biggest railway tunnelling projects in the country is the Udhampur-Srinagar-Baramulla Rail Link National Project. The project has been divided into three phases and includes the development of 38 tunnels with a length of 119.25 km. The first phase (Udhampur-Katra section) and the second phase (Qazigund-Baramulla and Banihal-Qazigund sections) have been completed. The third phase that covers the Katra-Banihal stretch is in progress. The Katra-Banihal project is one of the toughest projects undertaken in the country with 87 per cent of the rail line in tunnels. It involves the construction of 27 tunnels, one of which is the longest in the country at more than 12 km. It has also made a transition from D-shaped to elliptical tunnels and made use of the NATM technology. The project has faced many challenges mostly due to very difficult geological conditions of the young Himalayas, contractual difficulties and land acquisition issues.
Indian Railways (IR) also has a number of other projects – with 112 tunnels spanning a length of 81.96 km – at the planning stage. Some of the key upcoming projects are the
Mumbai-Ahmedabad Corridor and the Kolhapur-Rajapur projects in Maharashtra, the Kanhangad-Kaniyur rail line project in Kerala and the Bilaspur (Himachal Pradesh)-Mandi-Leh (Jammu & Kashmir) new line project. The Mumbai-Ahmedabad rail project is a high speed rail line project that will have a 21 km underground corridor including an underwater stretch of 7 km.
IR has a total investment requirement of Rs 8.56 trillion for network expansion and decongestion. There is also an increased focus on providing rail connectivity to the Northeast, and strategic and sensitive regions. The sector thus offers immense opportunities for tunnel development.
Metro rail tunnels
Of the projects tracked by India Infrastructure Research, the construction of around 171.52 km of metro tunnels has been completed, 51.18 km is ongoing and 5.02 km has been recently awarded. Delhi has the highest share of the total completed, ongoing and awarded tunnel length with tunnels spanning a length of 113.14 km. It is followed by Maharashtra and Tamil Nadu with tunnel lengths of 40.72 km and 38.69 km respectively.
TBM is the most widely used method for the construction of metro rail tunnels. This is followed by the cut-and-cover method and NATM technology. Many projects also deploy a combination of technologies for tunnel development.
Cities that have the maximum share of completed tunnels in the metro rail sector are Delhi, Chennai and Kolkata. Some of the important completed projects are the Delhi Metro, Phase III (Janakpuri West to Botanical Garden), Kolkata North-South Metro and Chennai Metro, Phase I (Washermanpet to Egmore).
Some of the key projects under construction are Mumbai Metro, Line 3 (Colaba-Bandra-SEEPZ), Chennai Metro, Phase I (May Day Park to AG-DMS) and the ambitious Kolkata East-West Metro which involves the construction of an underwater tunnel. The 502 metre under-water tunnel has been constructed using TBMs.
Tunnel construction in the sector is expected to pick up as more and more cities initiate metro projects. Many cities are planning to construct underground metro systems due to space constraints. Around 50 metro projects with underground stretches spanning a length of 1,070 km have been recently announced or approved. Some of the upcoming projects include the Bhubaneswar-Cuttack, Varanasi, Patna, Jaipur and Kanpur metro projects along with further expansion of the Delhi and Chennai metro networks. Some of the major challenges faced by developers are construction challenges while passing under residential and heavy traffic areas, land acquisition, contractual issues and lack of skilled manpower.
Water supply and sewerage tunnels
In the water supply and sewerage sector, India Infrastructure Research tracked 44 projects. Tunnels spanning a length of 214.99 km have been completed, 12.67 km of tunnels are under construction and tunnels of 15.23 km length have been recently awarded. In terms of length, Maharashtra has the maximum share of the total completed, ongoing and awarded tunnel length, followed by Delhi and Tamil Nadu.
The most commonly used technique for the development of tunnels in the sector is the TBM technology followed by DBM. The use of micro-tunnelling has also become popular and is being used for laying large diameter gravity sewers in cities where open-cut installation is difficult.
Some of the noteworthy projects that have been completed in the water supply and sewerage sector are the laying of interceptor sewers along the Najafgarh, Supplementary and Shahdara drains in Delhi, the Mumbai water supply project in Maharashtra and the Lower Nirar tunnel in Tamil Nadu.
Tunnels have proven successful in solving the water problems of many cities. Mumbai city serves as an example. The water supply network in Mumbai comprises old pipelines that are prone to leakages. Pipelines which pass near the seashore are also vulnerable to deterioration by saline water. Therefore, tunnels act as a better alternative and help in reducing water theft and transition losses. Tunnels have been developed to augment the city’s water supply and to improve the distribution system. These tunnels have a depth of around 50 to 100 metres and have been constructed using the full-face TBM technology. Among the key upcoming projects in the city are the tunnels under the Pinjal, Gargai and Damanganga-Pinjal National River Link projects.
Growing urbanisation and the government’s focus on improving basic services in cities through programmes such as the Smart Cities Mission and the Atal Mission for Rejuvenation and Urban Transformation will drive growth in this sector. Some of the important upcoming projects are the tunnel connecting the Khargi Hill and Pinjal reservoirs in Gujarat, the Koyna-Mumbai city intra-state link in Maharashtra and the Barakar-Damodar-Subarnarekha intra-state link in Jharkhand. However, challenges such as heavy ingress of water, demucking and restricted working hours along with safety of workers need to be addressed for successful project execution.
Conclusion
There is great scope for tunnel construction fuelled by the growing focus on infrastructure development. Metro rail tunnels will continue to be one of the biggest demand drivers of modern tunnelling equipment and technologies. This segment is expected to increase the use of TBM and NATM technologies and state-of-the-art equipment in tunnel construction.
Going forward, Indian and foreign joint ventures are expected to continue to bid for construction of tunnels and more players are expected to enter the market. However, there is a need to resolve pressing issues such as delays in land acquisition, contractual issues, lack of skilled manpower, etc., to ensure timebound and effective implementation of projects. It is also critical to carry out adequate investigations using advanced technologies to reduce geological uncertainties and risks and ensure timely execution of projects.