Another great way to get this is in Chapter 6 when you return to the main concourse where the Lightspeed Boy is (the giant spinning purple teletubbie statue) and just before you meet Ellie for the first time.
When you first enter the room, two enemies will constantly spawn on the other side of the room and charge towards where Ellie has the security door down and she'll blow them away. If you aim the launcher right, you can place a mine right in the path of one of the spawn points and the point where Ellie will blast away the necromorphs. If you have enough mines, the enemies will just keep running into them and you'll get the achievement to pop. I needed 10 more to get the achievement, had like 20 mines and got it easy with plenty of mines to spare.
Notes: Incase you miss a proper path point, you can just click RB to close the mine and then kinesis the mine back over to you.
Also, if you go far enough into the room where you get attacked by a crawler, the enemies will stop respawning and it won't work.