I think you guys are talking about the walk-through opening at the pier.

1778627536923.png

There is actually a trapezoid shaped void through the entire bridge. It is the inner formwork of the webs (white-ish colour in the middle). At the piers, where the reaction force is applied to the main girders, they need a solid section to carry this big, concentrated force from the pier below. They eek out a small opening through here so an inspector can walk the length of the bridge through the middle. Depending on the bridge segment length and curvature, they may similar solid pieces within the span as well (this looks like a curved segment and has at least one - also with passage for inspector to go through).
1778627689483.png
 
Since this time they did the tunneling before any station excavation instead unlike the first tunneled section. The new underground section would have side platform stations with tracks in the middle that anyone could walk over.
 
urbanclient said:
Is this a fact or are you speculating
Click to expand...
It’s a strange logical progression. I would argue there’s no chance any of these tunnelled stations gets side platforms.

1. With twin bored tunnels, the track centrelines have a minimum distance already sufficient for an island platform. Excavating additional space for side platforms is expensive.
2. There’s no way these suburban stations demand the added capacity of side platforms.
 
reinventingthewheel said:
It’s a strange logical progression. I would argue there’s no chance any of these tunnelled stations gets side platforms.

1. With twin bored tunnels, the track centrelines have a minimum distance already sufficient for an island platform. Excavating additional space for side platforms is expensive.
2. There’s no way these suburban stations demand the added capacity of side platforms.
Click to expand...
With centre platforms, they would save money on duplicating steps, escalators, and elevators. However, they should still have dual escalators & elevators for accessibility during maintenance.
 
reinventingthewheel said:
It’s a strange logical progression. I would argue there’s no chance any of these tunnelled stations gets side platforms.

1. With twin bored tunnels, the track centrelines have a minimum distance already sufficient for an island platform. Excavating additional space for side platforms is expensive.
2. There’s no way these suburban stations demand the added capacity of side platforms.
Click to expand...
I tend to agree with everything you said.

Conventional wisdom says side platforms have higher capacity. However, my experience in China is a lot of interchange stations have centre platforms for multiple lines (without cross-platform interchanging). If traffic is asymmetric, say 90% commuters eastbound in the morning, and 90% commuters westbound in the evening, then side platforms would be wholly unnecessary.
 
M II A II R II K said:
Speculating because side platforms are the norm when tunneling before station excavation.
Click to expand...
This is absolutely, positively not the case in the least. If it was, then wouldn't the currently open portion of the Crosstown have side platforms instead?

There simply is no correlation between construction scheduling and timing, and the location of the station platforms.

What there is a correlation between is the construction methodology - bored by multiple, parallel TBMs versus cut-and-cover - and the location of station platforms. And in the case of a line built using two bored tunnels, the platforms will always be in the middle - because as reinventingthewheel correctly pointed it, there is a minimum distance that the TBMs need to operate away from each other as they dig their respective tunnels. And that distance happens to nicely work out to be appropriate for a platform between them.

Dan
 
M II A II R II K said:
Speculating because side platforms are the norm when tunneling before station excavation.
Click to expand...
Sorry to call you out but it's pretty stupid of you to think like that since the Crosstown was built in this exact order. Oppose to the TYSSE where they excavated first but they ended up with centre platform too.
 
You must log in or register to post here.

Back
Top