09 July 2020

Table of Contents for Project Focus

Interaction- R. Anantakumar, EVP & BU Head – Urban Transportation, Afcons Infrastructure

Afcons will be the first Indian company to build underwater Metro

AFCONS INFRASTRUCTURE a SP Group company is set for a milestone by tunnelling underneath river Hooghly for the East-West Metro Project in Kolkata. AFCONS is among India’s top infrastructure companies and has executed remarkable projects in India as well as in various parts of the world. R. ANANTAKUMAR, EVP & BU HEAD – URBAN TRANSPORTATION, AFCONS INFRASTRUCTURE offered CONSTRUCTION OPPORTUNITIES a close view of India’s first under water metro tunnel project being executed by his company.


Afcons is the first Indian company to build Metro infrastructure under water in Kolkata. What made you take up this unique challenge?

Afcons has played a significant role in nation building by consistently delivering iconic and technologically challenging projects in India and abroad. It is the first Indian company to construct an underground Metro tunnel using top-down methodology without any foreign JV in New Delhi (Barakhamba Road Metro Station). Afcons is also the only company, in India, to qualify for Metro tunnel construction using TBMs on its own. It is constructing India’s biggest underground Metro station at Chennai as part of Chennai Metro project. The three-storey station will serve as an interchange, and, connect commuters with suburban and long-distance trains and bus services.

Afcons has consistently shown the gumption to tackle complex projects, and we’re excited in playing a leading role in the East-West Metro Project in Kolkata. We are in the process of building an underwater tunnel below the bed of Hooghly River for the Kolkata Metro Rail Corporation Ltd (KMRCL).Afcons will be the first Indian company to build underwater Metro infrastructure facility.


How is building an underwater tunnel different from building an underground tunnel?

In general, underground tunnelling is a very challenging task but underwater tunnelling adds more complexities and risks. Due to working underwater, the risk of water ingress increases and impact due to geological surprises is also very high. Once the tunnelling starts under the river bed, it should not stop under any circumstance. In underwater tunnelling, bore has to be dug much deeper due to possibility of water inflow. This requires very high level of detailing, precision and preparation.


Please tell us about the extensive groundwork that was undertaken before the actual tunnelling work.

At the outset, we had to select suitable designs and technologies for the successful delivery of the project. The designing of this project was entrusted to specialised world-class design companies such as ATKINS, SYSTRA and Tunnelconsult. We chose Herrenkeneckht Tunnel Boring Machines (TBMs) for this project, based on their track record in manufacturing machines tailor-made for specific project requirements. Herrenkeneckht is also engaged in maintenance of the two TBMs deployed for the Kolkata Metro project. We are working together to ensure flawless delivery of the project, especially the under-the-river stretch.

KMRCL had carried out soil investigation work at the pre-tender stage for feasibility study. In addition to this, we carried out soil investigation work near the entire tunnel alignment, deploying floating barges and pontoons in the river portion. We have also conducted extensive condition surveys of the buildings in proximity to the alignment before carrying out tunnelling.


What have been the surprises that the geological survey of river bed has thrown so far?

There have been no surprises thrown so far with regards to the geological survey of the river bed. The tunnels will be constructed along the safest layer below the river bed.


What are the eventualities that you are anticipating in your journey under the bed of river Hooghly? How have you equipped yourself to handle these situations?

We are not anticipating any surprises. However, we are well prepared and have taken all possible precautions and measures. We have a team of highly-experienced tunnel crew on board, should an entry into the cutting chamber be required under high hyperbaric pressures during river driver. In the remote possibility of river water ingress, the TBM is designed to shut down like a submarine, for safe evacuation.


Is the underwater Metro tunnel under the river Hooghly going to be modelled over similar projects in the world, like the Thames tunnel or Sydney Harbour?

Each underwater crossing has its own challenges and different geological features. So, one cannot really model a crossing based on what has already been achieved. We have, however, looked for precautions taken and problems faced in different river crossings as well as projects that have been executed in extremely high water bearing conditions and applied this to our own geological situation that we will encounter.


Have any innovations been made as part of this project?

We have done a number of innovations and have improved upon numerous processes while planning the project.

Due to site constraints the TBM has to be driven through Howrah Station in advance. This is a delicate operation where the TBM can encounter difficulty in crossing the diaphragm walls. We designed a “Soft Eye” of styrofoam replacing M-40 concrete. This has worked extremely well. This is a first design of its kind attempted in India by our in-house design engineers.

At Afcons, we follow the culture of continuous improvement through innovation.


What took so long for India to come up with a project of this nature?

The experience of the existing Metro corridor in Kolkata and the success of the Delhi Metro network contributed to the sanctioning of the second phase of the Kolkata Metro that will have the underwater Metro tunnel. The tunnel, which runs underneath river Hooghly, is aimed at connecting Howrah and Sealdah railway stations, two of the busiest railway stations in the world.


This is a momentous feat in terms of Metro infrastructure. What have been the other highlights in India’s Metro infrastructure space before this?

First thing that comes to mind is the sheer scale of projects being envisioned. The gap between concept and actual execution is shrinking rapidly. We have incorporated world's latest and best practices in our design and implementation processes thereby delivering savings in time, cost and space.

Our engineers have rapidly scaled up their skills to utilise the best practices with minimum gestation.

Metro rail first arrived in India as early as 1984 with the north-south Kolkata Metro. But the rush for Metro infrastructure actually began after its success in Delhi. It was the first time in India that tunnels were constructed for Metro using TBMs. It changed the outlook and future of Metro construction in India. We expect a similar impact with the underwater tunnelling by Afcons.


Does Afcons have projects similar to this in the pipeline, given that you are making Metro infrastructure in several other cities in India?

We have recently been awarded the underground Metro projects in Ahmedabad. We have completed two underground projects in Chennai Metro. It is a matter of pride for us that Chennai Metro Rail Ltd (CMRL) chose us to takeover abandoned underground projects. This clearly demonstrates the confidence we enjoy from various clients in the country.

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