Crossrail tunnel portal near Stratford

ABB125

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I went past the tunnel portal just before Stratford (Pudding Mill Lane?) and noticed that the crossrail tracks seem to rise out of the ground by about a metre more than seemingly necessary before sloping downwards to the same level as the rest of the tracks into the station. In other words, the tracks exit the tunnel onto a ~1m high embankment, then drop down to "ground level". Does anyone know why this is? There must be some rational explanation.
Thanks
 
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fat_boy_pete

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16 Mar 2015
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Essex
I went past the tunnel portal just before Stratford (Pudding Mill Lane?) and noticed that the crossrail tracks seem to rise out of the ground by about a metre more than seemingly necessary before sloping downwards to the same level as the rest of the tracks into the station. In other words, the tracks exit the tunnel onto a ~1m high embankment, then drop down to "ground level". Does anyone know why this is? There must be some rational explanation.
Thanks
Flood barrier? E.g. if surface tracks were flooded by run off, they are prevented from draining into the tunnels, but will drain over the side of the embankment instead
 

swt_passenger

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I think I remember an article saying it was to do with smoothing the change of gradient. Because they had to get under the River Lea, but over the “Greenway” in a relatively short distance, and you can’t have sharp changes of gradient, the only practical solution was effectively to overshoot the necessary level and come down again.

I don’t think the anti-flooding theory is a good one, as it doesn’t appear to happen at any other portal?

(For those who don’t know, the “Greenway” is hiding a major sewer - basically considered as an immovable object, I expect if it had been possible there’d be a much lower gradient.)
 

ABB125

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I think I remember an article saying it was to do with smoothing the change of gradient. Because they had to get under the River Lea, but over the “Greenway” in a relatively short distance, and you can’t have sharp changes of gradient, the only practical solution was effectively to overshoot the necessary level and come down again.

I don’t think the anti-flooding theory is a good one, as it doesn’t appear to happen at any other portal?

(For those who don’t know, the “Greenway” is hiding a major sewer - basically considered as an immovable object, I expect if it had been possible there’d be a much lower gradient.)
Thanks - that's probably it then.
 

davews

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While doing a walk along the Greenway recently where it passes the line to West Ham a bit further along at a bridge I wondered what they did to the sewer pipe underneath the bridge. As you say it is a pretty immovable object (despite its 'pleasant' smells)
 

edwin_m

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Nottingham
While doing a walk along the Greenway recently where it passes the line to West Ham a bit further along at a bridge I wondered what they did to the sewer pipe underneath the bridge. As you say it is a pretty immovable object (despite its 'pleasant' smells)
The pipe can just dive down, under and up. As long as it's sealed top and bottom, the contents will continue to flow through.
 

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