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Old October 21st, 2010, 09:07 AM   #1
netcupeter
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Axis deviation for motorways tunnels

Hello!

I recently discovered this forum and already have a question. :-)

I have to design a motorway with tunnels.
The tunnels are two separated tubes at 11.00 meters from the central axis.
My problem is that I don’t know from what point to begin the deviation of the central axis, what distance to put between starting point and the end of the axis deviation?
I attached a picture to illustrate better my problem.
http://picasaweb.google.com/netcupet...74846696253522

Also I would like to know a European Norm in which is written the distance for axis deviation for motorways.

Thank you in advance,
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Old October 21st, 2010, 09:38 AM   #2
RawLee
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I suppose the angle of the deviation has something to do with design speed.
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Old October 21st, 2010, 09:55 AM   #3
netcupeter
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I suppose so to, but I don't know the minimum or maximum of this angle.
The design speed in that area in 120 km/h.
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Old October 21st, 2010, 11:34 AM   #4
keber
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There is no defined angle but just regulations about horizontal elements (straights, easements, circular arcs) at given design speed and terrain conditions.

There are different regulations about designing roads (and motorways) in each country as there is no uniform EU regulation about this.

Also, tunnel tubes separation is defined by geological conditions and is measured by tube axis to tube axis and tube cross section.
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Old October 21st, 2010, 05:01 PM   #5
Fargo Wolf
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Quote:
Originally Posted by netcupeter View Post
Hello!

I recently discovered this forum and already have a question. :-)
http://picasaweb.google.com/netcupet...74846696253522

Also I would like to know a European Norm in which is written the distance for axis deviation for motorways.

Thank you in advance,
I think the tapering should not be any sharper than 1:20. For every 20 meters of distance, the horizontal distance would be 1 meter.

As for where to begin the deviation, it would probably be best to allow for a tangent distance of about 100 to 200 meters IF possible after exiting the tunnel to allow drivers to readjust to daylight conditions, before starting to taper the two roadways together.

Hopefully this will be of some help to you.
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Old October 21st, 2010, 05:02 PM   #6
J N Winkler
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As a general rule, each carriageway by itself has to meet the geometric design criteria appropriate to the facility type and design speed. So if you have to insert a curve or combination of curves in order to obtain the required distance between carriageways, that curve or those curves have to be designed in accordance with the geometric design criteria. As others have noted, these geometric design criteria will specify:

* Minimum horizontal curve radius

* Maximum superelevation

* Superelevation and curve transition length for a given choice of horizontal curve radius (which itself is arbitrary as long as it is not lower than the minimum radius)

* Minimum sight distance (be careful with this, if you put a curve in near the tunnel portal while the roadway through the tunnels themselves are on tangent)

There are higher-order considerations of design consistency, but if you are going to SkyscraperCity for curve design advice, you are not too worried about those, are you?
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Old October 22nd, 2010, 09:56 AM   #7
netcupeter
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Thank you very much for your answers.
The problem is that in ISPOL (road design software) I have only one axis and I can’t geometrically design two axes for each carriageway.
The program can split the carriage way to a given distance. I took in consideration some norms and I came with a distance of 1500 meters to pass from 0 meters to 22 meters between carriageways.
I have the space to make the transition in 1500 meters so I think is ok. ;-)
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Old October 22nd, 2010, 12:43 PM   #8
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Horizontal and vertical alignment is different in a lot of countries, even compared to the design speed there are remarkable differences between guidelines in numerous states.

Buy an official guideline of the country where the tunnel is projected, I would suggest...
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Old October 22nd, 2010, 04:27 PM   #9
Fargo Wolf
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Quote:
Originally Posted by netcupeter View Post
Thank you very much for your answers.
The problem is that in ISPOL (road design software) I have only one axis and I can’t geometrically design two axes for each carriageway.
The program can split the carriage way to a given distance. I took in consideration some norms and I came with a distance of 1500 meters to pass from 0 meters to 22 meters between carriageways.
I have the space to make the transition in 1500 meters so I think is ok. ;-)
That's LOTS of room. You'll be able to do the transition with room to spare.
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Old October 22nd, 2010, 08:16 PM   #10
Wilhem275
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Yep! Look at this example: the italian A12, from Genoa towards Rome (although never completed...). Many tunnels, all built with separated tubes for geological reasons.

The distance between the tubes is about 20-22 m, but most of them may seem closer from the sat photos, since the presence of bridges forces to shrik the distance between the tubes.

In this picture you can see a clear example:
http://goo.gl/maps/09ew

The distance between the tunnels and the point where the lanes merge is about 200-250 m.
Design speed 130 km/h.


On that hw you can actually see some bizarre designs, like a junction split in two by a tunnel
http://goo.gl/maps/7VV7

Or a junction which takes 3 km to reach any road
http://goo.gl/maps/yxHH
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Last edited by Wilhem275; October 25th, 2010 at 02:56 PM.
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Old October 25th, 2010, 09:19 AM   #11
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Very good exemple!
Thank you very much!
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