India is one of the fastest growing markets for tunnel construction

Kapil Bhati, MD, Robbins Tunneling India, says apart from metro and water projects, hydro-power projects also provide a big business opportunity for tunnelling.

Where is the most tunnelling activity taking place at present?
Underground works in urban areas are the need of the hour. Mostly, all the cities in India are developing their underground metro transit systems, but Delhi is the first city to initiate this level of development and tops the chart. Phase-III of DMRC envisages 140 km of metro systems, out of which 50 km is underground. Chennai, Bangalore, Kochi, Jaipur, Lucknow, Ahmedabad and others join the list later.

What are the metro systems where you have been involved and where else will you be working?
Robbins India debuted in the year 2005 as a wholly owned subsidiary of the US based The Robbins Company. Since inception, we have supplied and worked in many water irrigation tunnels and metros across India. Robbins started with Delhi metro Phase-I, supplying two EPB TBMs, and then joined hands for Chennai Metro with AFCONS. Subsequently, Jaipur Metro came along and Robbins is now working for the Bangalore metro. Robbins has also been actively working in water irrigation projects and supplied three 10-m diameter double shield machines in Hyderabad and one hybrid machine in Madhya Pradesh. It completed a water transfer tunnel in Mumbai, using a 6.25-diameter main beam TBM and created an Indian record of boring 876 m in a single month. The Indian tunnelling industry has huge prospects and we see ourselves working in Mumbai Metro Phase – III, Lucknow Metro and Ahmedabad Metro, respectively.

What has been the experience so far in using TBM in India?
India is one of the fastest growing markets for tunnel construction. Tunnelling with tunnel boring machines (TBM) has proved to be cost-effective and a faster alternative to the old drilling and blast method (DBM). TBM has been found suitable for any type of rock and geology. A positive factor in favour of TBM is faster and smooth tunnelling without much disturbance to the surrounding rock mass.

What are the global advances in TBMs?
In order to overcome hurdles due to hard rock, we have developed a new type of TBM which are named the Crossover series. This machine features the characteristics of both single shield hard rock machines and EPBs for efficient excavation in urban areas.

What are the opportunities in the hydro-power sector in the Himalayan region?
India has an immense hydro-power potential to the tune of 84,000 MW, a major chunk of which is in the Himalayas. The surge in power demand in the country has necessitated an increased thrust on development of hydroelectric projects in India. This is growing daily.

What are the geological challenges of tunnelling in the Himalayas?
Tunnels are important elements of infrastructure projects and are used in hydro-power, transportation, water supply and sewerage systems, etc. Their construction involves many complexities in terms of different shapes, soil, rock conditions, alignments, etc.

Himalayas are a mountain chain with complex geologies. The tunnelling activities in various projects here are impacted by diverse geological problems such as different terrain conditions, thrust zones, shear zones, folded rock sequence, ingress of water and geothermal gradients. The tunnelling methods used are: i) Conventional Method; ii) Mechanised Method. Drilling & blasting and New Austrian Tunnelling Method (NATM) are conventional methods while the latter includes Road headers and TBMs. All these methods are widely used across different sectors.

What are the new technologies and equipment used?
Factors that determine the selection of method to excavate a tunnel depend upon the geology, economy and sociological factors. At times, geological factors affect the economics of a project. In the present scenario, all the methods mentioned above are readily used and popular for making tunnels in hydro projects, water irrigation, transportation and sewerage systems.

What is the importance of geo-technical site investigations?
Unforeseen ground conditions represent a huge area of risk; construction contracts either have to allocate the risk to a single party or share the risk with them. The traditional method of controlling such risks has been through the use of thorough site investigation and competent geo-technical designs, aiming to produce a robust scheme, well matched to the expected ground conditions.