I used the shovel in a random point of the map and a black pillar come out growing in height and becoming larger and larger builinda a real black wall that divides the map in two?? I'm the only one? 

This is a troll dig spot next to Uniform. The pillars will keep growing until you break the original pillar at the dig spot. I can't remember exactly, but I think you'll need to break the rest manually - unless it's changed in 0.7.0.

Yah... this is intended. Your save might be effectively screwed at this point as the pillars are likely to spread faster then you can eliminate them.

you found one of the few scenarios that actually effectively game-overs you (digging it up and not keeping an eye on it)
you can try to get busy smashing it with a crowbar/knife... or maybe the pickaxe is effective against it, but I think that's too much at this point, you've doomed the world kel

object and event reset might remove it but I've not tested it, your choice if you want to persist in your doomed save or try to fix it. If you do an object and event reset, make sure you put all the items you care about into the mailbox and save first.