A way to get Tilemap as 2D array in code?

Is there a way to get a tilemap into code, to then have check stuff, change it, and apply it to the tilemap again?

In short, I want to make a small game where some blocks can fall and interact with other tiles. Thus my need to check for the custom "physics" and apply them every so often (currently fixed update set to run 5 times a second). Is there a way I can get the tilemap as a 2D array and manipulate it? I'd also need to know which tile is which, if possible.