Rail service and travel by rail in India and Bangladesh

[jis]

In the past we have discussed the use of expansion joints in rail tracks. In India it is a standard to have expansion joints at each end of long welded segments. Typically these are seen adjacent to interlocking plants I found this very clear view in a video which I thought would be worth sharing to illustrate these so called double switch expansion joints.



The location is Masagram East interlocking on the Howrah - Barddhaman Chord (HBC) section of the Kolkata - Delhi route. This track is technically cleared for 160kph (100mph) operation but is speed restricted to 130kph (81mph) for commercial operation because the complete fencing that is required to produce a sealed corridor is not completed yet. You can see the fencing that is in place in the background. At this specific point the speed limit on this track is 75kph due to construction work involving this track which includes installing a switch and removing an existing switch (see below for the reason).

Masagram East is undergoing major modification as a connection is being built to a new branch suburban line to Bankura. When completed Masagram will become an inter-zone station with HBC in Eastern Railway and the new branch in South Eastern Railway zone.

You can look it up in Google Map. Currently HBC is triple track through Masagram, but is soon going to be quadruple track as the fourth track is extended west from Chandanpur. You can see the groundwork for the fourth track on the left side of the frame. Eventually, after the Dedicated Freight Corridor is built through here in all it will become a six track railroad two suburban tracks, two express tracks and two freight tracks..

 

[cirdan]

Could it be that the reason for these joints is to provide some sort of electrical isolation between segments for signal and detection purposes?

 

[cirdan]

They have generally followed streets or other ground that do not have significant buildings on them in order to minimize disturbance to the building foundations. It is difficult to know what will happen if foundations built in mud are disturbed. Multiple rerouting leading to trying to tunnel under buildings possibly led to the collapse between Esplanade and Sealdah several years back. An underground spring completed the fiasco. Currently apparently the Westbound Tunnel which was affected has finally been completed, and work is in progress to plug the hole in the ground through which the TBMs were recovered at that point.

I don't know about India, but in the legal systems of some countries land ownersip also means you technically own the subsoil going a long way down. Property owners can thus block tunneling projects even if these have no noticeable impact. This is the reason that in London for example, most of the underground bits of the Underground run below streets and public land (and there are some pretty tight corners).

It doesn't really help much against subsidence IMHO as soil adjacent to the construction activity is often just as prone to subsidence as soil directly above.

 

[jis]

Could it be that the reason for these joints is to provide some sort of electrical isolation between segments for signal and detection purposes?

Standard insulated joints are used for that purpose. These are for expansion and there is no specific insulating function.

I don't know about India, but in the legal systems of some countries land ownersip also means you technically own the subsoil going a long way down. Property owners can thus block tunneling projects even if these have no noticeable impact. This is the reason that in London for example, most of the underground bits of the Underground run below streets and public land (and has some pretty tight corners).

It doesn't really help much against subsidence as soil adjacent to the construction is just as prone to subsidence as soil directly above.

India generally follows British practices. The government has to buy/lease easements from property owners, and usually such contracts include clauses protecting the property owner from damage caused by the use of such easements. That is why all the people displaced by this fiasco are being housed in apartments temporarily until the equivalent of their original accommodation can be built after the situation is stabilized in the original property locations. KMRC is paying for their housing and displacement. They will also build new houses/apartment buildings in the original locations replacing everything that has been damaged by subsidence..

In Kolkata the existence of a aquifer so near the surface that had not already been drained by tube wells surprised everyone. There are plenty of subsidence problems due to simply aquifer depletion due to pumping of water through tube wells around there., and those are typically from much shallower layers, which have more or less been bled dry. The big tube wells used now are much deeper than the depth of the rail tubes under the Bow Bazar area.

When they are able to get access to road alignments, first choice is to go elevated. If they must go underground, which they try to avoid as much as possible since that costs much more, unless there is reason to go deep, they tend to use diaphragm walls to protect against land displacement and use cut and cover, since it works out to have more predictable outcomes even though it inconveniences the users of the road that is dug up. There are significant hazards to building underground structures in a delta that is barely stable. The big bridges are all built on stabilized "floating: caissons (floating in mud essentially) since there is no rock layer to go down to for miles.