Thanks Mcadambi for this info.

This was bound to happen - 3 crore projects replacing 50 crore projects would certainly reduce margins & seriously jeopardize the interests of many construction cos., many who whom may even be surplussed out. Serves them right - they have already had their heydays & it's now time for faster & cheaper solutions.

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we have had some heavy rains already..any updates on how these underpasses are holding out?

There were some initial drainage issues..are these managed now?

3mts width is just right for a pedestrian underpass only..we need to have a min width of 5 mts atleast for any more underpasses! 

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Well...the Magic Boxes werent much of a solution. They are like a temporary structure! Why not look for a mix - a solution close to a permanent flyover/underpass but using pre-cast technology. L&T did it at NH4/BIAL interchange in 5 months! The Magix Box can be a temporary solution that acts as a side road untill the main flyover is built.

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Narayan,

Magic Box widths upto 6.0m are possible (two lanes). The ones put up at Cauvery & BDA Jns are narrower (3.5 & 4.5m).

L&T did not do the entire job within 5 months. I had been monitoring the construction activity there. It had been on since the past two years. Piers & Ramp construction activities & much of the ground work had already made a lot of progress six months back, but was moving ahead at snail's pace then. Also, there was a court case over a piece of land required for one of the ramps. The activity gathered pace in the last 4-5 months with the opening of BIA drawing closer.

In any case, the Magic Boxes are of great utility since costs are minimal + installation is fast. So, even if they are of low height, I feel they are acceptable & should be used as they can save huge amounts.

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Your right Naveen, 6 meter magic boxes can be a workable solution. I was thinking for the Ring Road - every junction can be made signal free. The magic box underpasses can be in sections so that each land has one section of the underpass. This way you can even keep a hieght barrier on them to restric two wheelers & cars from busses & trucks.

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Just for record, these are the current dimensions of the magic box elements.
note this is the clear available space within the box.

Cauvery Jn - 4.25m (14.025 ft)
BDA Jn - 5.5m (18.15 ft)
Anand nagar - 3.5m (11.55 ft)
Cunningham road/sanky road intersection - 3m (9.9ft)

I have mentioned the dimensions in feet as it can be easily visualized
Please feel free to add the vehicle dimensions and the "safe" gap that should be maintained to ensure smooth travel thru the magic boxes

It may be noted that as the width of the magic box increases the structural strength of the element must be increased.
Has there been any study on at what is the maximum width that a magic box can be built vs the cost of conventional construction it will be interesting to note the same.
This study can revolutionise the logic of building underpasses and flyovers.

-- Praveen Sundaram AkA PhotoYogi

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Photoyogi /Narayan,

In general, any method of pre-fab construction that avoids casting on site will always reduce construction time & costs & be superior since casting, testing, etc. can all be done off site in better, more suitable conditions, avoiding time pressures. Correspondingly, costs will also be cheaper. This includes bridge construction - huge suspension bridges such as those across Tokyo Bay, Japan & in Denmark across the Danish straits were also built in this manner.

However, handling, transporting & positioning very heavy pre-fab elements is what poses limitations. For over 6m width of elements, weight of each element may be in excess of 100 tons due to the very sturdy structures necessary. Transporting these on road & shifting & positioning them will be a huge task, possibly impossible in bangalore, unless very wide roads are available at site & heavy handling gear is operable.

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