Accounting for differing grades around retaining walls

Something I've had issues with while using the software is accounting for cuts and fills on either side of a retaining wall. In some cases the grade on one side of the wall may differ by up to 18' and I cannot seem to find a good method for translating that to the program. I've tried various methods of creating the retaining wall as a feature surface, as a 1' wide path and even using the raise feature. Even playing with the side batter numbers the program seems to always leave a ditch on the higher side of the retaining wall that is difficult to calculate a cut or fill for. When trying it as a feature surface, using an outline of "Define Varying Levels" seems to do the best job as I can set the grade on the high side and the low side separately but the program still leaves a space unaccounted for. Setting the wall as a break line inside of another feature, i.e., a sub grade in a grass area, also seems to make the grades around the break line go bonkers. One thing I've been able to do about that is set point elevations in the areas that are causing trouble but most of the time I am just making an educated guess at those point elevations and the problem still remains.

I'm curious if others have had this issue and what they've done to combat it. Or maybe there is something in the program that I'm missing that would better account for the placement of a proposed retaining wall. If the "Path" feature allowed me to set differing elevations on either side of the wall, and also account for proposed contour lines, I feel like it would be a good solution for the problem I'm having here. One thing to note is that I do not have access to CAD files when I'm creating my models, so I'm doing this purely based on the information provided in the plans available for a specific job which are sometimes not the best.

I've attached an example of a job where I was having this issue for folks to review and possibly advise. One factor I am unsure of on this particular job is if there is any sort of reveal on the high side of the retaining wall at any point. Typically I would have to wait to win the bid for the job and obtain a shop drawing from my wall subcontractor before I have specific information on these things.

Attached Files

  Cuts Fills V2.kcp (Size: 1.95 MB / Downloads: 3)

Hey Ken, 

I think I can help here. Retaining walls can definitely be one of the more challenging grading situations to model, particularly when there are large elevation differences between the two sides and limited design information. 

You're on the right track with the breaklines. A workflow we recommend is to model the retaining wall using two breaklines within a single feature surface:

• One breakline represents the top of the retaining wall.
  
• The second breakline represents the toe (bottom) of the wall.
  

In your project specifically these will need to live within the 'Grass Areas' Feature Surface. 



Because breaklines allow individual points to be left unset, Cubed will interpolate those elevations from neighbouring points making it easier to model retaining walls with varying heights without having to manually assign every elevation. 

Once you've defined either the top or bottom of the retaining wall, I'd recommend using the Offset tool to essentially duplicate it. You will just need to offset it by a certain amount and reassign the elevation values, then you'll have generated the corresponding breakline with identical geometry.



Regarding the road section in your example, the same principle applies. The roads shown at the top demonstrate how to add breaklines where they are implied by the terrain, rather than explicitly shown on the plans. The shape of the contours often indicates where a change in grade occurs, and adding breaklines along these locations allows the surface to better represent the intended design.



For retaining walls, adding breaklines along the top and bottom of the wall helps the surface hold the line, preventing the terrain from smoothing across the wall and producing the incorrect ditches or gaps that you've been seeing.

With TW only: 



With TW and BW: 



We have a video tutorial that walks through this workflow step by step. It demonstrates how to create retaining walls using breaklines and the Offset tool, along with some best practices for modelling more complex grading situations.
Retaining Walls in Kubla Cubed 

I will add that having looked at your project, I believe there are some issues arising from the way you have chosen to structure your elements. If defined in the same phase elements override each other.  In your project you could use this to create a considerably clearer mesh, rather than trying to 'punch out' gaps for other elements or define complex boundaries for the grass, which is causing issues with retaining definitions. The 'element colors' view is very useful when doing this.  Lower elements in the list override higher ones.  This method is discussed in the context of a housing project in this video  

Kubla Cubed Walk-Through | Calculating Cut & Fill For Housing Projects


Hopefully this provides a more reliable workflow for the type of projects you're modelling. If you have an example where this approach still doesn't produce the expected result, we'd be happy to take a look at the model and offer more specific guidance.

Leah