box push each other by physics?

I am creating a scorched earth style game but the ground is made of rectangular boxes.
Boxes underneath can explode and boxes above fills the hole due to gravity.
What would be the best set up for this?
As a test, I just created first row of boxes from script, but once they are created, they appear to push each other slowly to make small gap between them.
Box prefab has rigidbody2d and boxcollider2d.

edit: more details.
My blocks look like this:

i removed the bottom 3 blocks and 3 blocks above it came down thanks to gravity but other 4 blocks didn’t because i changed drag to like 30. If i leave drag at 0, blocks all collapse like this


how do i make the ground stable and come down vertically smoothly without them pushing each other horizontally?

Use Iskinematic property of Rigidbody2D or hight value of drag and angular drag. Can you explain me in detail what behaviour you are expecting from Boxes? If possible attach snapshot also.