With 24/7 multi-mode surveillance and rapid response BP teams, somehow an attempt to bore/grind/dig through, could become known as a very foolish thing to do.
I predict that Mexico, which is in a big hurt right now, will seek any means to repair relations with the US to the point of stationing its troops at the border to assist calls from US BP command posts.
The would-be border busters could face a bigger threat from the Mexico side.
What you describe is a metaphorical wall
It can be put in place when Trump makes an offer the mexican president dares not refuse