The government has reiterated its focus on infrastructure development time and again. In the recent past, greater emphasis has been given to the development of water and sewerage, road, irrigation, railway, metro rail and hydropower projects. This bodes well for the tunnelling market, as it will open up fresh business opportunities for the segment.
Indian Infrastructure looks at the opportunities for the tunnelling market across various sectors…
Hydropower tunnels
On the basis of the projects tracked by India Infrastructure Research, as of August 2017, 135 projects spanning 335 km are under construction while 604 projects spanning 1,103 km have been planned in the hydropower segment. In addition, around 268 projects spanning 696 km are currently stalled. The upcoming projects offer a construction opportunity of Rs 551 billion-Rs 662 billion for the tunnelling sector. A state-wise analysis indicates that the maximum opportunity is offered by Arunachal Pradesh with 242 projects (475 km), followed by Himachal Pradesh with 122 projects (299 km) and Uttarakhand with 90 projects (184 km).
Tunnels have been playing a key role in hydropower development. Some of the longest tunnels in the country are in hydro projects. Till date, more than 500 km of tunnelling has been completed in the segment. As three-fourths of India’s hydropower potential lies in the Himalayas, several important hydro tunnelling projects such as Dulhasti, Kishanganga, Uri I, Parbati II, Tapovan Vishnugad, Maneri-Bhali, Loktak, Ranganadi, Nathpa Jhakri and Teesta V have been undertaken in the region. However, tunnelling in the Himalayan region poses a huge challenge due to topographic and geological complexities, which result in unexpected events during construction.
The tunnelling experience in the past has been somewhat mixed in nature, with successes as well as pitfalls due to unprecedented problems. Success stories of the Loktak, Chamera I, Uri Stage I, Nathpa Jhakri and Kishanganga tunnels have been noteworthy while the problems encountered in the construction of the Ranganadi, Dulhasti, Parbati II and Tapovan Vishnugad tunnels are eye openers. Some of the longest upcoming hydro tunnels are the 32 km tunnel for the Parbati hydroelectric project (HEP), Stage II; a 14 km tunnel as part of the Lohari Nagpala HEP; a 12 km tunnel in the Tapovan Vishnugad project; a 14 km tunnel as part of the Kameng HEP; and a 12 km tunnel in the Singoli Bhatwari project.
Over the years, tunnelling for inter-basin transfers, multi-purpose projects and pump storage projects has been gaining prominence. An increasing use of state-of-the-art investigation techniques such as remote sensing-based mapping, invasive geophysical investigation, deep drilling, directional drilling, etc. has also been witnessed. Initially, the drill and blast method (DBM) was the main technique adopted for the excavation and support of hydropower tunnels. With the passage of time, mechanised hydro tunnelling gained prominence and was deployed in the construction of the Loktak, Parbati II and Kishanganga hydro tunnels.
Long hydro tunnel projects in India have suffered from delays and cost overruns due to geological problems such as sheared or crushed rocks with seepage, ingress of water and crushed rock fragments/silt, squeezing conditions or stress-induced failures, high geothermal gradient and emission of noxious gases. In addition, inaccessibility due to rugged topography and geomorphic conditions, high superincumbent cover, infeasibility of drilling sufficient number of boreholes or excavating sufficient number of drifts, and lack of adequate tools to identify deep-seated shear zones or weak rock mass have also posed challenges in hydropower tunnelling.
In order to ensure the successful implementation of hydro tunnel projects, there is a need to undertake comprehensive investigations, careful blasting, detailed rock mass characterisation and instrumentation; select the right methodology, agency and crew for tunnel construction; and ensure regular interactions among designers, geologists, site engineers and contractors. Also, proper risk identification and management processes need to be put in place.
Water and sewage tunnels
According to India Infrastructure Research, as of August 2017, five tunnelling projects spanning 56 km are under construction while 21 projects spanning 168 km have been planned in the water and sewerage sectors. The upcoming projects offer an opportunity to the tune of Rs 67 billion-Rs 84 billion for tunnel construction. State-wise, Maharashtra leads with 23 projects spanning 215 km in the pipeline, followed by Tamil Nadu with two projects (5 km) and Jharkhand with one project (5 km). Tunnels have proven to be suitable for supplying water across cities, a case in point being Mumbai.
The water supply network in Mumbai comprises pipelines, some of which are 80-100 years old. These pipelines are susceptible to leakages and, hence, require regular maintenance. Also, the pipelines which have been laid close to the seabed are prone to deterioration due to saline water. In such a scenario, tunnels provide a viable solution as they are maintenance-free and tamperproof, therefore ensuring that there is no chance of water theft. Tunnels also result in a reduction in pressure and transition losses.
In Mumbai, a few tunnels have been constructed for the augmentation of water supply while several others were constructed for improving the water distribution system through the replacement of old and damaged water pipes. These water tunnels are about 50-100 metres below ground level and have been constructed by means of full face tunnel boring machines (TBMs). Till date, more than 83 km of water tunnels have been commissioned and made operational, 6.36 km are under progress and 124 km are at the planning stage.
The existing water tunnels in Mumbai include the 7 km tunnel from Modaksagar Dam to Bifurcation Chamber, the 5 km tunnel from Bhandup Complex to Kandivali, the 0.7 km east side and 1 km west side Kasheli Creek tunnels, the 1 km Bhandup Complex to Saddle tunnel, the 3.87 km Race Course to Malabar Hill tunnel, the 3.87 km King Circle to Sewree tunnel, the 4.96 Ruparel College to Race Course tunnel, the 12.04 km Bhandup Complex to Charkop tunnel, the 6.12 km Veravali to Yari Road tunnel, the 3.63 km Malabar Hill to Cross Maidan tunnel, the 12.28 km Maroshi to Ruparel College tunnel, the 6.77 km Modaksagar dam to Bell Nallah tunnel and the 15.1 km Gundovali-Bhandup Complex tunnel. Further, the 6.36 km tunnel from Powai Yard to Veravali and Powai to Ghatkopar high level-low level reservoirs is currently under construction. Water tunnelling projects in the planning stage are the 9.7 km tunnel from Amar Mahal to Wadala-Parel, the 5.1 km tunnel from Amar Mahal to Trombay high level-low level reservoirs, the 17.49 km Bhugad-Khargi Hill tunnel, the 25.22 km Khargi Hill-Pinjal tunnel, the 64 km Pinjal-Gundavali tunnel and the 2.5 km Gargai-Modaksagar tunnel.
The Municipal Corporation of Greater Mumbai encountered several issues and challenges in the construction of water tunnels across the city. These include heavy ingress of subsoil water, dewatering and restrictions on drainage of pumped water as well as restrictions on drilling and blasting. Demucking has also emerged as a key challenge due to non-availability of space for dumping in the city. Lastly, restricted working hours have also impeded the sound execution of projects.
Road tunnels
On the basis of projects tracked by India Infrastructure Research, as of August 2017, 25 tunnelling projects spanning 61 km are under construction while 75 projects spanning 338 km have been planned in the roads and highways sector. In addition, four tunnel projects spanning 16 km are currently stalled. The upcoming projects offer a construction opportunity of Rs 507 billion-Rs 676 billion for the tunnelling sector. A state-wise analysis indicates that the maximum opportunity is offered by Jammu & Kashmir with 21 projects (148 km), followed by Maharashtra with 15 projects (89 km) and Himachal Pradesh with 22 projects (51 km).
At present, one of the most important road tunnel projects under execution is the 8.8 km Rohtang tunnel. Once completed, it will become the world’s longest tunnel at an altitude of over 10,000 feet. Several issues have been faced in the construction of Himalayan tunnels such as the alignment crossing below glacial lakes, construction through crystalline thrust, varying geology, high ingress of water, low temperatures,
difficulties in muck disposal, etc. Tunnelling in such regions faces multiple, often unforeseen, problems such as face collapse, chimney formation, water inrush, hot water springs, gas explosion, squeezing and so on. The Rohtang tunnel is no exception, and has witnessed 18 major collapses over a period of three years.
In order to bring about an improvement in the construction of road tunnels, especially in difficult terrains, emphasis needs to be laid on understanding the basics of rock mechanics. Sound investigations and exploration are of the utmost importance. There is a need to adopt new methods of investigation on a case-to-case basis. Also, data sharing to facilitate knowledge dissemination and the creative use of muck waste for highway construction should also be encouraged.
Irrigation tunnels
According to India Infrastructure Research, as of August 2017, six projects spanning 52 km are ongoing while 40 projects spanning 643 km are in the planning stage for the irrigation sector. The upcoming projects offer an opportunity of Rs 418 billion-Rs 450 billion for tunnel construction. State-wise, Rajasthan offers the maximum opportunity with three projects spanning 290 km, followed by Maharashtra with 14 projects (244 km) and Andhra Pradesh with one project (19 km).
At present, the Parwan multi-purpose irrigation project is one of the most important projects being undertaken in the sector. In May 2017, the project was awarded to the joint venture of Hindustan Construction Company Limited and Hoisto Structurals and Equipment Private Limited on an engineering, procurement and construction basis by the Rajasthan government’s Water Resources Department. The project, worth Rs 6.73 billion, envisages the construction of a concrete gravity dam and a 8.47 km tunnel for irrigation and water supply purposes. It is expected to be completed within 48 months from the date of award.
Irrigation projects are subject to several delays on account of inadequate planning at the detailed project report stage, lack of prompt decision-making, labour-related issues, deficient construction machinery, financing issues, political and regulatory issues, natural causes, and deficiencies in contracting practices. In order to ensure the sound implementation of irrigation projects, detailed planning is of the utmost importance. There is a need to optimise the sequencing of construction in order to fast-track it. Also, the practice of putting the entire onus of risks faced from the tender finalisation to the project execution stage on the contractor must be discouraged to prevent delays in project execution.
Railway tunnels
According to India Infrastructure Research, as of August 2017, 164 tunnelling projects spanning 251 km are under construction while 115 projects spanning 181 km have been planned in the railway sector. In addition, 29 projects spanning about 23 km are stalled. The upcoming projects offer an opportunity to the tune of Rs 109 billion-Rs 163 billion for tunnel construction. State-wise, Jammu & Kashmir leads with 29 projects spanning 105 km in the pipeline, followed by Uttarakhand with 81 projects (100 km) and Manipur with 46 projects (54.5 km).
Till date, around 586.95 km of railway tunnels have been constructed across the country. Of the total, tunnels spanning 94 km have been operationalised in Himachal Pradesh, followed by 82 km in Kerala and 72 km in Tamil Nadu. Some of the major railway tunnels include the 11.3 km Pir Panjal tunnel, tunnels spanning 11.55 km as part of the Jiribam-Tupul-Imphal railway project, around 100 km of tunnelling under the Rishikesh-Karnprayag railway project, 84 km of tunnelling as part of Konkan Railway and the Mumbai-Pune railway line, etc.
Data suggests that the majority of the ongoing and completed tunnels are, or have been, excavated using DBM (299 tunnels), followed by the classical method (107 tunnels) and the New Austrian Tunneling Method (NATM) (58 tunnels). This is due to the fact that most of the railway tunnels are constructed in difficult terrains in the Western Ghats and the northern and northeastern regions. Going forward, DBM is expected to continue its dominance over other tunnelling techniques while the use of NATM is also likely to pick up.
Metro rail tunnels
According to India Infrastructure Research, as of August 2017, the construction of around 110 km of metro tunnels is ongoing, 281 km is planned and 136 km has been approved. The upcoming projects offer an opportunity of Rs 290 billion-Rs 1,940 billion for tunnel construction. State-wise, Uttar Pradesh offers the maximum opportunity with 72 km, followed by Delhi and Tamil Nadu with 71 km each.
TBMs are the most commonly used technique in metro rail construction. These machines were first used for Phase I of the Delhi Metro. Subsequently, metro projects in Bengaluru, Chennai, Jaipur, Lucknow, Mumbai (Line 3) and Kolkata also put TBMs to use due to inherent construction challenges in urban areas. In the recent past, several important developments have taken place with regard to metro tunnels. To date, tunnelling through TBMs for 40 sections of the Chennai Metro has been completed. Further, 36 km of single tunnels has been completed in Phase I while 3.6 km of drive through tunnels has been completed under the Phase I extension. With regard to the Mumbai Metro, Line 3 tunnel, TBMs had successfully completed 1,267 metres of tunnelling at various station sites as of April 2018. 17 TBMs are expected to be put into use by July 2018.
Challenges encountered during the construction of metro tunnels include the selection of the most appropriate method/technique for tunnel construction, unexpected geological complexities and safety risks, inadequate investigation of ground and soil conditions, high capital costs of specialised equipment like TBMs and adverse environmental effects of tunnelling using DBM.
Conclusion
The future for the tunnel development market is promising. Growth will be largely driven by the central government’s focus on infrastructure development. The robust pipeline of infrastructure projects on offer translates into an optimistic future for the tunnel development market. However, there is a need to ensure that the factors that can slow down the execution of tunnelling projects are dealt with in a time-bound and effective manner.