[damper99]

Yep. A barrier is only effective when covered by fire.

[nvscanman]

Bingo....

[RavenLooneyToon]

Have Engineering Corps dig very straight trenches 50 feet wide by 12 miles long, only ten feet deep, no structures or materials needed.
Monitored by lasers.
Break the beam, and a rail gun launches 5 lb round of solid titanium at supersonic velocity. Direct hit will vaporize; anything else will be killed by the shock wave.
Patrol with choppers.