Personally I’d set up minefields then open it up to public bidding and a lottery.
As far as a wall goes it could easily work and was manned with heavily armed individuals and a lot of sensors. Tunnels will always be attempted with some successful but tunnels are fairly easy to find and GPR is one of may ways to detect them.
I have an idea for a downward directed shaped charge mine that could put an end to tunneling, too, without causing surface problems...