An Experience With This Iconic Bridge
In Conversation with Er. Shishir Bansal
After much discussion, the final shape was conceptualized, where after a few meetings, with Charles Correa and Jorg Schlaich, Subbarao, Ratan Batliboi, and other eminent Engineers and Architects, the decision regarding the shape was finalized and we started working on it.
We took the necessary permissions from the DTTDC Board of Directors and appointed Jorg Schlaich as the consultant with Construma Consultants as the associated partners for foundation’ works, Ratan Batliboi as the architect plus Michel Virlogeux as the Engineer (who was also the structural engineer for Milau Verdict in South France) as we had invited him to India for a lecture at the ICI, and we requested him, and he agreed to be associated while finalizing the design and concept of the Bridge. He was one of the eminent international engineers available at that time.
And thus the Project Began
By pre-qualifying the consultants, and getting sanction from the government, we had already made an estimate based on the previous concept of a simple cable stayed bridge and we had received a sanction of ` 459 Crores but the design had now been changed to an Iconic Bridge. The one thing that was not decided at that time was that instead of calling more tenders, we would call one single global tender. After a discussion with the government, we attempted to convince them that the approaches are not that tough or high-tech and our Indian Contractors could do it but if we go for international bidding for approaches, then we will end up with a very high price but the government did not agree and we invited one International Bidder and as expected the price was very high (but in fact the quoted price was not as high as it should have been). So then due to various circumstances, we had to call for another tender.
Soon after, we found out that the bigger trouble was of forest clearance, a good part of the Bridge was lying within dense forest cover and we initiated the forest clearance in 2007, the first letter to the government for this approval, written by me was when I was the Superintending engineer. In this project I started as the Superintending Engineer, then the Chief Project Manager. It took us a total of five years to get the forest clearance.
It was a dense forest, so dense that it was too difficult for us to do a detailed soil survey but we completed the detailed soil investigation, and to our utter surprise, one of our vital foundations, where the backstay was supposed to be, the rock was slopy, the rock beneath that area was a sharp sloping rock. In a well of 70 dia, it was sloping by 9 metres and it was not possible to rest our back stays there, our foundation would have then become unsuitable (for that particular location) and so we had to make a new design. By the time this problem occurred, we had already completed other foundations and there was absolutely no possibility of shifting our location because the foundation was done, sub-piers were done and so we had to find a solution, then and there. After much study and consultation with the experts, we all agreed that we can go for integrated well-pile foundation.
We took the matter to the board and after a series of meetings and discussions and finally we got it approved in 2014. In December, the machinery came to site. Before bringing the machine, the company had said that one would be able to finish 32 piles in about 5-6 months but it took us 16 months because the moment we started drilling, all the soil began collapsing during boring. So we had to take out the machine, flush the bore, reinstall the machine, and then redo it - and not only once, sometimes twice, sometimes thrice as well. In fact we completed 31 piles in 13 months but 1 pile was stuck as the chisel got disengaged from the crane and was stuck in the passage. Digging was not possible. Somehow the location of the pile was favourable to us or else we would have (with the consultants’ agreement) abandoned the pipe as it would have not made much of a difference.
But I had an idea that even after doing all this piling we had to plug the well, we had to open it from the centre. Once we open the centre we can make a passage and take the chisel out from there, and it did work! So while we plugged and took out the chisel we also ended up clearing the passage, I had thought that if we have cleared out the passage then why not put in this pile as well. Why we should abandon it? So then we put in the last pile also and completed this process in April 2016. And after that everything went smoothly without any delay.
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