you might not want to go with a Tilemap at this point and prototype by creating an actual map with sprites as your tile. you can build a simple double for loop that spawns tiles and create a “tiled” map. You could also possibly get away with creating squares(3D box BSP) that have fracture on them and do this as your tile and use a material on them so you can get a more “breaking” kinda thing. the only thing is you’ll be stepping away from 2d into 3d but you will be using 2d in your texture and camera. so it’s faked 2d. as it normally would be with this engine anyway.
If you’re dead set on using a tilemap, What you can do is access specific tiles on your tile map and change the tile from being the ground to being an “exploded” version from a different “tile set”. You can probably do this with the projectile doing a collision check, play a flipbook at the place of collision, then swap out the tiles below the flipbook but I’m not sure what you’re really trying to do so I can’t give anything specific. just vague ideas and rants. hehehe
Good luck on your venture, friend!