Carving non-linear spaces into Brep?

Hello,

I'm currently working on a group project, and we are using Grasshopper and cannot figure out a definition for our intent? The best way I can describe it is by using this picture by BIG for a bridge project they did. Essentially, we are also doing a programmatic bridge, and our circulation paths need to be non-linear as well as capable of intersecting/interweaving with one another. Similarly to how in the example on the bottom right with the two arrows.

I have tried "carving" these spaces out from a Brep by literally carving them out or using curves to specify the spaces. But it is far too clunky for our project's circulation.

Thank you!