Problem Closing Breps to create a solid object

Hello, I’m trying to cut this object using 2 boxes and everytime I do, it’s leaving open faces, I believe this is because before hand, It is an open brep and I’ve been trying for ages to close the brep so when I subtract the shapes, it doesn’t leave open faces, if anyone knows how to fix this, It’d be greatly appreciated



Tunnel of smoothness.3dm (7.9 MB)
Tunnel of smoothness.gh (19.4 KB)

The file I uploaded is broken as I accidentally deleted some of the refs, but if anyone knows how to I can fix this, it would be amazing, I think that after I do the sweep1 to create the surface, I then need to make the brep into a solid, but I can’t find anywhere on the internet that tells me how to do such a thing

Tunnel of smoothness Edited V0.gh (28.4 KB)
First, you need to make your sections planar(red).
Second, Trim Solid will leave open Brep, instead use Solid Difference.

Thank you so very much, that fixed my problem perfectly