Switchback road - boundary intersect

Switchback road - boundary intersect

Crass
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Message 1 of 9

Switchback road - boundary intersect

Crass
Collaborator
Collaborator

Hi - I am designing a tight radius driveway on a steep slope. Some weird stuff is happening as the corridor grades back to itself and it is not resolved very nicely. See the attached screenshot. Almost the entire road is in cut. Do you think this is an issue with my assembly? Any guidance would be greatly appreciated. Thanks!

 

switchback driveway.jpgswitchback driveway_2.jpg

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AutoCAD 2018/2021
AutoCAD Civil 3D 2021
Accepted solutions (1)
2,351 Views
8 Replies
Replies (8)
Message 2 of 9

Jeew-m
Mentor
Mentor

Hi,

Is it possible to attach the dwg?

Thanks

 



Jeewana Meegahage
Design Engineer
Autodesk Civil 3D Tutorials
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Message 3 of 9

Crass
Collaborator
Collaborator

Hi. See the drawing file attached. Thanks for looking into this!

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AutoCAD 2018/2021
AutoCAD Civil 3D 2021
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Message 4 of 9

samir_rezk
Advisor
Advisor
Accepted solution

Hi @Crass 

 

The corridor assembly sampling was overlapping so I used the Clear Corridor Bowtie command to clear up the overlapping area. Also increased the frequency quite a bit so get a good sampling along the curvature. attached is the modified file. 

 

capture.png

 

Hope this helps,

 


Samir Rezk
Technical Support Specialist

Message 5 of 9

neilyj666
Mentor
Mentor

The slope is too slack on the right hand daylight - I amended it to 2V:1H.

 

I also split the corridor into 3 regions and increased the sampling distance to 5' from  25' as 25' won't give the detail required around the bend. For a final design I would copy the assembly, change the slope and sample distances for the copy and apply to the middle region only 

neilyj (No connection with Autodesk other than using the products in the real world)
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AEC Collection 2026 UKIE (mainly Civil 3D UKIE and IW)
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Message 6 of 9

Crass
Collaborator
Collaborator

Hello @samir_rezk Thanks! This is just what I was looking for. I haven't used the clear bowties tool before. This looks handy. I will keep the frequency in mind as well.

 

 
 
 
 
i
 - Thank you as well.
 It think the 0.5:1 side slope is a little steep for this site though.
 
 
 
 
 
 
 
 
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AutoCAD 2018/2021
AutoCAD Civil 3D 2021
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Message 7 of 9

Crass
Collaborator
Collaborator

@samir_rezk- I tried to replicate exactly what you did. I think I even selected the same Clear Corridor Bowtie point but my result is still a little wonky compared to your. See attached images. Anything I am missing in the process?

switchback driveway_4.jpg

 

switchback driveway_3.jpg

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AutoCAD 2018/2021
AutoCAD Civil 3D 2021
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Message 8 of 9

samir_rezk
Advisor
Advisor

Hi @Crass 

 

In full disclosure, I also added all the top defining feature lines as a surface definition in the corridor properties/surface tab. The top links are not enough to have an accurate definition! The feature lines are imperative in giving the surface a linear definition, where the top links provide a sectional definition.

hope you get better results when you add them


Samir Rezk
Technical Support Specialist

Message 9 of 9

neilyj666
Mentor
Mentor

@Crass Yes 0.5:1 is steep and will depend on the strata present but the steepening technique can be useful if the strata is competent as it will reduce the excavation task but the bowtie clearance method suggested by @samir_rezk  is the one to go with

neilyj (No connection with Autodesk other than using the products in the real world)
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AEC Collection 2026 UKIE (mainly Civil 3D UKIE and IW)
Win 11 Pro x64, 1Tb Primary SSD, 1Tb Secondary SSD
64Gb RAM Intel(R) Xeon(R) W-11855M CPU @ 3.2GHz
NVIDIA RTX A5000 16Gb, Dual 27" Monitor, Dell Inspiron 7760