In the past few years, proactive efforts have been made to rapidly expand the country’s railway network. Several new railway line projects are being undertaken in the previously underpenetrated regions of Jammu & Kashmir and the Northeast to provide seamless connectivity and a reliable mode of transport. Further, high speed rail projects have also been launched to modernise rail services and reduce travel time between major cities. This has led to a substantial increase in tunnelling activity in the railway sector. Several projects involving the development of tunnels are being undertaken by Indian Railways. Many of these are being implemented in the Himalayan geology, which is one of the toughest in the world in which to construct and maintain underground structures. As of April 2019, there are around 594 rail tunnels in the country with a cumulative length of over 234 km.
Key ongoing and upcoming projects
Several railway projects that are currently under way or are at the planning stage involve the construction of tunnels. One of the biggest railway tunnelling projects being undertaken is the 272 km Udhampur-Srinagar-Baramulla rail link project. It involves the development of 38 tunnels with a total length of 119.21 km. While the Udhampur-Katra, Qazigund-Baramulla and Banihal-Qazigund sections of the project have been completed, the Katra-Banihal section is in progress. This section is one of the most difficult projects to be undertaken in the country with over 85 per cent of the rail line in tunnels. It involves the construction of 27 tunnels, one of which, at over 12 km, will be the longest in the country. Further, the other ongoing railway projects that entail tunnel development include the Jiribam-Tupul-Imphal, Sevoke-Rangpo, Rishikesh-Karanprayag, Bhairabi-Sairang and Bhanupali-Bilaspur new rail line projects.
The upcoming Mumbai-Ahmedabad high speed rail project also involves the development of 21 km of tunnel length between the underground station at the Bandra-Kurla Complex and Shilpata in Maharashtra. The tunnelling works include the development of a 7 km undersea tunnel. Other key upcoming projects with tunnelling activities include the Bilaspur-Mandi-Leh, Kanhangad-Kaniyur, and Haryana Orbital rail corridor projects.
New trends and developments
While the drill and blast method continues to be the most commonly used for development of railway tunnels, new techniques such as the tunnel boring machine (TBM) and the New Austrian Tunnelling Method (NATM) are also gradually gaining traction. Projects that involve the use of advanced tunnelling methods include the Mumbai-Ahmedabad high speed rail project, which has been planned using a combination of NATM and the TBM technique. Of the total tunnel length under the project, around 15.41 km will be developed using the TBM method while 4.88 km will use NATM. Besides, the construction of tunnels under the 51.38 km Bhairabi-Sairang new railway line project in the Northeast also involves the use of NATM due to weak soil and rock strata conditions.
A key development has been the inauguration in September 2019 of the country’s longest electrified tunnel between Cherlopalli and Rapuru stations in Andhra Pradesh as a part of the 112 km long Obulavaripalli-Venkatachalam railway line. The 6.7 km tunnel has been constructed to provide seamless rail connectivity between Krishnapatnam port and the hinterland areas for faster freight movement. The tunnel features a ballastless track with bi-block sleepers and Vaslo fittings. Besides, LED lighting has been provided every 10 metres in the tunnel along with two traction power supply substations located near Cherlopalli and Adurupalli. Further, in the past couple of years, there has been an increase in the adoption of new survey technologies such as drones, satellite imagery and Light Detection and Ranging (LiDAR) surveys. The deployment of these technologies can help in obtaining accurate data and planning and designing projects properly. The Mumbai-Ahmedabad high speed rail project is the first railway project in the country to use the aerial LiDAR method for conducting the survey works. Moreover, a static refraction technique survey was carried out for the undersea tunnel in the Thane Creek area.
The ongoing pandemic has affected the timelines of several railway tunnel projects. While construction of ongoing projects was delayed, the bidding process for several upcoming projects including the Mumbai-Ahmedabad high speed rail project and the Rishikesh-Karanprayag new rail line project was postponed. Further, with physical distancing measures in place, contractors will have to work towards deploying digital solutions and increasing automation to prevent the spread of COVID-19.
The way forward
Tunnel activity in the railway sector is expected to increase in the coming years with the expansion of the railway network. The implementation of new high speed and semi-high speed rail projects such as the Pune-Nashik semi-high speed rail project and the Kerala semi-high speed rail projects are also expected to give a fillip to tunnel construction. This will provide ample opportunities to contractors, technology and equipment providers and other ancillary segments. However, tunnel projects are quite complex and delays in construction of tunnels cause railway projects to languish for years. It is, therefore, important to resolve issues such as delays in land acquisition, contractual issues, inadequate investigations and lack of skilled manpower to ensure timely execution of projects.