Indian tunnelling has gained sufficient experience in tunnelling, and as new infrastructure projects in rail, metro rail, water and hydro electric projects promise momentum underground, technology and management will be critical, write Rajaji Meshram and Dhruv Gadh.
"Tunnel Vision", as the metaphor goes, may not have a very positive connotation to it, but for some infrastructure firms this term may represent a niche opportunity that could well see investments of more than $10 billion in the next five years.
A key driver of this opportunity is going to be the need for underground development for expanding mass urban rail transit systems in India. The scale of growth of this sector can be visualised by the fact that till the year 2000, the only underground metro network in India was the 17 km stretch in the north-south line of Kolkata Metro. Since then, thanks largely to the development of Delhi Metro phases 1 and 2, the operational underground network in India has expanded to over 65 km.
More importantly, the learning and benchmarks set in Delhi Metro project is now helping faster development of projects across India. The current projects under implementation across Bangalore, Chennai, Delhi and other cities are expected to add another 100 km of underground network in the next 2-3 years.
With the 12thFive Year Plan recommending metro network development in cities with population greater than two million, there is an opportunity for development of metro networks across a number of Tier I and Tier II cities. Many of these have already announced plans for construction of metro projects and as a result, development of over 1,100 km of metro network across 23 cities in India is currently under various stages of development/planning. However, underground metro network costs are 4-5 times higher than the elevated metro network. As seen in chart below, the planned costs for underground tunnelling across various metro projects ranged from Rs 80 to 144 crore per km based on type of tunnelling while those of elevated corridor were about Rs 20 to 30 crore per km. In addition to the cost, construction of underground metro in cities also has technical challenges of managing alignment owning to presence of existing network of water supply/sewerage pipes, electricity cables, telephone cables etc. Thus underground tunnel mode for developing metros is chosen only when the development of elevated network is not feasible owing to issues like congestion, land acquisition, unavailability of space for civil work etc. This has been the case in Delhi metro network where the proportion of underground network has been increasing in each phase of development - about 20 per cent in Phase 1, 28 per cent in Phase 2 and about 40 per cent in Phase 3.
While majority of this network would be over ground, unavailability of space and other issues of land acquisition, congestion etc would necessitate construction of underground network in many of these projects. Thus, given the current plans, the development of underground network and stations should see an investment of $4 billion in the next few years.
An equally large and probably strategically more significant opportunity in underground tunnelling lies far away from urban regions - in the mountainous terrains of Himalayas, stretching from Jammu & Kashmir (J&K) to north-east India. Whether it is the opportunity to harness energy from various water sources through hydro units, the need to develop connectivity for efficient movement of people and goods through rail networks or the necessity of round-the-year access to key border regions, the need for tunnel infrastructure is critical.
With over 19 GW of hydro power additions in the last 15 years, engineering, procurement and construction (EPC) players have long been tapping the opportunity for development of HRT, TRT, underground power houses etc, in the hydro sector. With over 13 GW of hydro projects currently under construction, over 300 km underground tunnels need to be constructed in the next 5-7 years.
National priority projects in rail like Jammu-Baramulla in J&K and Sivok Rangpo and Brynhiat-Shillong in north-east have significant tunnelling requirement. The recently completed Pir Panjal tunnel on the Jammu-Baramulla rail line, the longest rail tunnel in India and second longest in Asia, has showcased IndiaÆs ability to deliver on projects of such scale and engineering complexity.
As part of the long term planning for strategic connectivity to key border regions, the Border Road Organisation plans to develop over 100 km of road tunnels. The 8.8 km Rohtang tunnel is already under construction and 6.5 km Z Morh tunnel has been recently awarded. Tendering process for 12 km long Zojilla tunnel has also been initiated.
The water conduit
Tunnelling opportunity also exists in water supply and water sewerage sector. Historically, the most common technique used to lay water and sewerage pipelines has been open excavation. However, open excavation method is slowly losing its popularity as it causes significant disruption to on-ground activities especially in highly populated areas. Hence, more and more tunnels are now being dug using trenchless techniques like micro-tunnelling, augur method, horizontal displacement methods etc. In a few cases where large volumes of water are to be transported over long distances, tunnel boring machines (TBMs) are also used.
In irrigation, instead of clearance of large land masses for developing canals, many of which pass through ecologically sensitive zones, the option of digging tunnels is being slowly exercised in India. The state of Andhra Pradesh, with 4-5 large tunnelling projects totalling over 350 km, is at the forefront of this development.
While tunnelling opportunity exists across various sectors, the technological, people and engineering challenges that exist across urban metro projects and rough terrain road/rail and hydro projects are very different.
A typical metro project takes about 3-4 years for construction versus hydro projects which has a typical construction period of 5-6 years. The pace of tunnelling work, which forms a major component of hydro power plant development, has a notable bearing on the pace of the implementation of the project.
In metro projects, owing to existing bore holes, sewerage and underground systems, the amount of information available on soil type, ground conditions etc is significant. For most projects in Himalayan terrain, however, the detailed discovery of ground and environmental conditions only happens during drivage of tunnels. Due to the difficult terrain, desired number of bore holes and other surveys are not possible during investigation stage.
This results in not only delays and cost overruns, but also, sometimes, has more severe consequences like loss of life. A case in point is the development of the 105 MW Loktak hydro project in Manipur where inflammable gasses were discovered during tunnelling, leading to loss of lives.
The Himalayan geology is quite varying with folds and large number of small and big faults, thrusts, and shear-zones. Moreover, the rocks of Shiwaliks and Lesser Himalayas - the key regions where majority of projects are being planned, are jointed, sheared, fragile and weak. These together make Himalayan rocks a difficult tunnelling media. Thus, while TBMs are used extensively in metro projects, the TBM has not been able to gain a wider acceptance in sectors like hydro, rail and road tunnels owing to complexities in geological conditions. For example, while developing the 11 km long Pir Panjal railway tunnel in J&K, the engineers had to face the challenge of eight different types of geological strata and to meet the challenge the New Austrian Tunnelling Methodology (NATM) was adopted for tunnel construction.
Other major projects, like Rohtang tunnel too have faced delays owing to issues like seepage and water inflow in tunnel. The tunnelling in Veligonda irrigation project came to a halt for several months as the TBM got stuck owing to collapse of roof.
In addition, political and labour challenges of working in tough and sometimes hostile terrain are problems that developers need to tackle. Thus, while large tunnelling companies in the world may be eyeing opportunities in this sector, large and medium sized Indian firms which have a local presence and have experience of both technical and people dynamics, have been able to capture market share in this niche sector.
Despite the technology and execution challenges, there is, literally, significant business and light at the end of the tunnel and experienced Indian developers are well equipped to tap this opportunity.