Modeling Loop Alignment Surfaces for a Tunnel Ramp

This one came in today and is one of those that keeps coming up periodically - a loop alignment for a ramp and some 3D lines from which to form a surface model and how best to handle the problems associated with this type of surface

Plan View

3D View

The video below shows how to model these types of surfaces. The challenges with these are the following

  1. The cross over area - you have lines that loop around and cross over themselves and each other creating 2 elevations at every crossing - these will create both flags in the surface and an erroneous surface in the cross over location - you have to split out either the higher or lower section in the cross over so that this doesn’t happen

  2. Limiting the surface so that it doesn’t have triangles in the loop area center or outside the edges of the model - you can either use a Null Surface Texture and or Surface Boundaries to limit the model to what you need.

In this case the Pavement crossover is a square of about 8x8m - you can either give the machine operator a second surface for that area or he can typically grade that in by eye between the areas that he can do with Automatics - your call how to address that in the machine.

Hope the video helps

Alan how does this null site improvement work? What are the triggers for it to function? is it name, layer, material or a combination of those? Handy trick regardless, I wasn’t aware of this one.

You assign a Surface Texture to a closed area of a surface defined by a line with Sharp and Texture property - do not pick a material - leave it blank - TBC reads that as Null the Triangles - this is like placing an internal boundary on a surface - the Triangles are still there but they are hidden