Topic: Vertical cross section of a Tunnel pipe problem

[ekoneo]

Hi all,
I prepare a small tunnel corridor model. The radius is 4m.
The tunnel's profile has a %5 vertical profile slope. I finished the model. I draw all sections.
Then I try something. I increased the slope up to %60. I know this impossible condition for a tunnel construction.
But I wonder that what happens on the model.
All corridor sections are consisted vertically. So the tunnel radious goes smaller.
However the tunnel radious becomes smaller, the section drawings shows the radious 4m.
How can I draw the sections that are perpendicular to the profile slope?

[mjfarrell]

Hi all,
I prepare a small tunnel corridor model. The radius is 4m.
The tunnel's profile has a %5 vertical profile slope. I finished the model. I draw all sections.
Then I try something. I increased the slope up to %60. I know this impossible condition for a tunnel construction.
But I wonder that what happens on the model.
All corridor sections are consisted vertically. So the tunnel radious goes smaller.
However the tunnel radious becomes smaller, the section drawings shows the radious 4m.
How can I draw the sections that are perpendicular to the profile slope?

I don't think your models shows what you think it does....
Let me test here...is the tunnel bottom flat, than an arched section?

[mjfarrell]

here...

[ekoneo]

I try to sketch it below

[mjfarrell]

how or what did you use for your circular assembly?

there are at least two good ways- sub assembly by polyline....or generic links....have fun working out the slopes for that one!

[ekoneo]

I increased your profile slope. I make the section interval distance 5m.  I rebuilt your corridor. Then I upload here.

[ekoneo]

I made it with subassembly from a polyline.

[mjfarrell]

I increased your profile slope. I make the section interval distance 5m.  I rebuilt your corridor. Then I upload here.

Move my sample line to any station and the cross section is normal....i.e. I don't see any problem with the model

[mjfarrell]

if one uses the DRIVE command it does 'appear' to be wrong...however that is just a perception.

[ekoneo]

The problem is cross sections shows normal. But corridor sections are not perpendicular to the profile line. They are perpendicular to Y axis.
Although radious decrease, the crosssection shows normal. I need the cross section that is perpendicular to the road profile line.

[mjfarrell]

sounds like you would be wanting to use EXTRUDE and SLICE to get sections from a solid...not roadway sections..

or provide ample of what you have, and what you think you want...

I'm pretty sure the software is performing as expected...

[ekoneo]

I atached a photo from your corridor. On vertical side tunnel becomes thin. But Tunnel corridor width and height should be constant.

[mjfarrell]

oblique/vertical exaggeration  i.e. Don't trust your eyes on this one

[mjfarrell]

from side view................same size....

[ekoneo]

Hi mjfarrell,

I think about your last post during a long time.
Then I had a question myself..
I try to sketch it.
In the sketch,
The train's height is not parallel to your measurement direction. If the slope increase the tunnel height become smaller than the train's height (theorically).

[mjfarrell]

I think you are 'over' thinking it....a 4 meter bore is still a 4 meter bore irrespective of the incline the boring machine is working at.

Also consider that no sharp changes in deflection either horizontal or vertical are going to happen.
This both so the boring machine can negotiate the turn AND the train cars.  Otherwise every subway in the world would be plugged up with stuck trains right now.

[mjfarrell]

OK, I now see the issue. Much more clearly...

The cross section is projected perpendicular to the alignments with the controlling alignment being the Horizontal NOT the vertical alignment...and yes this distorts the

tunnel section. 

Good luck on any change to that coming from Autodesk.

Also I don't see any easy fix for this....However As stated earlier, on could resort to standard 3d solids EXTRUDE, or SWEEP command to model the tunnel and other features.

OR...and I have not tried this....Rotate the UCS and model this thing on it's side.....it may take a left and right version.

[ekoneo]

Thanks mjfarrell.
It seems difficult
As a result of my internet researches, i read a little tip from autodesk forum.
http://forums.autodesk.com/t5/autocad-civil-3d-general/tunnel-corridor-becomes-shrink-on-very-high-vertical-slope/m-p/5485676#M266618

As BrianHailey said In SAC, there is a way to set the profile slope value to a parameter.
If it is possible to distort the subassemblies depending on that parameter, I can get correct result.
Unfortunatelly it seems complicated for me 

[mjfarrell]

one could do a similar thing by setting a target profile for the top of tunnel to follow...without SAC.