5 replies to this topic

[jis]

 

https://bdnews24.com...ridge-installed

 

The Padma Bridge is being built spanning the Padma River. This channel carries most of the water flowing down both the Ganges and Bramhaputra draining all of North India and the Tibet plateau, essentially all the water that carries down from the Himalayas east of Simla. Allegedly, it has a greater flow, specially during Monsoon, than any single channel of even the Amazon in its estuary. Padma at this point (a rather narrow portion of it) is a bit over 6km (about 4 miles) wide and more than 100m (~325 feet) deep in places, with unusually rapid flow so close to the sea, and rapidly moving sedimentary formations.

 

The main bridge consists of 41 spans 150m each (almost 500') carrying one (160kph/100mph passenger 120kph/75mph freight) rail track in a run through truss with planned capacity of 40 train per day initially going up to 4tph eventually after electrification, and a deck above the truss carrying a four lane highway. Each of the 42 pylons sit on piling driven into the river bed as much as 400m ((1,300') below the bed. The bridge is designed to withstand earthquakes of upto magnitude eight.

 

Upon completion of this bridge and the related railroad connection to Jessore, travel time from Kolkata to Dhaka will go down to below four hours (from the current 8+ hours).

 

If things stay on course it will come in at the third most expensive bridge in the world. The project is currently funded about 2/3rds by China through a loan and 1/3rd by Bangladesh.

 

Incidentally it is likely that the 4th through 6th span at the south end of the bridge will go up within the next couple of months. The they wills tart installing spans on the north end while the redesigned pylons to account for clay at the bottom of the river are constructed mid river.

 

A betting man would guess that the bridge structure may be completed and ready for use by late 2019. The initial rail connection to India from this bridge will be via Bhanga - Faridpur - Kushtya (near where it joins the current route of the Dhaka - Kolkata service via the Gede border.

 

For reference, here is a map:

 

Edited by jis, 02 April 2018 - 04:43 PM.

[Bob Dylan]

Too bad the poor little US can't afford to build anything anymore except Berlin Type Walls! 🤔

Edited by Bob Dylan, 02 April 2018 - 04:30 PM.

[jis]

Well, the New York East Side Access Project is a technically remarkable, and remarkably overpriced project. The San Francisco Bay Bridge replacement is a great one too, though not as hard to build as this one.

 

The Gateway Project if and when it happens will cost way way more than this bridge but won;t be anything as remarkable as it, unfortunately. Hudson is a very pretty but really tiny river.

[Metra Electric Rider]

NPR's Marketplace had a program (ok, well, ok, a piece about) about tunneling costs in Nu Yawk. Way higher than anywhere else.

 

So the bridge is basically between Dhaka and Faridpur, more or less, on the map?

[jis]

The core bridge route is from Dhaka to where the green line ends south of Faridpur, that is Bhanga. The actual 6km bridge is across the stream that passes close to Faridpur but south of it, by Bhanga. The other stream closer to Dhaka (Burhiganga) used to be once upon a time, a major channel of the Ganga. It is not any more. The route will of course cross that too, but not on something considered a major bridge. Just around 1km or so, and pretty shallow flood stream mostly.

 

Major movement of streams and channels is a major headache in bridge building. They have to train the river to stay in its channel and not decamp somewhere else. To give you an example of huge channel movements, Bramhaputra which comes in from the north and joins the Padma a little north of Faridpur, Back in the mid 18th century it used to flow mostly through a channel flowing into the Meghna River which flows on the east side (right of Dhaka), and there was very little flow into the main Ganga channel Burhiganga  nearer Dhaka, from Bramhaputra. The current Padma Channel was a lesser channel. All these flows got shuffled after a major earthquake in the late 18th century raised the Mymansingh Plateau slightly, causing the Bramhaputra to flow further west and join the Ganga where it does today, and convert Padma into this Godzilla channel that it is today.

 

Consequently, there is about a total of a hundred miles of river bank protection and training work involved to ensure that the darned river continues to flow under the bridge after it is built, rather than somewhere else.


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Edited by jis, 06 April 2018 - 05:12 PM.

[Metra Electric Rider]

Funny you should mention the shifting channels. I was trying to locate the bridge on google maps and on bing maps and the channel was totally different in each of them. Google maps showed the piers of the bridge construction. I was just reading about why the Amazon has no bridges - they would need to be 30 miles long for the high water periods to be able to make it across the flooded channels....