Recently on Reddit I have been seeing a lot of sculk mines. They appear to be pretty easy to make once you have the necessary parts, so I decided to make some.

I have come across a bit of a problem. In the videos showing how to build these, they have multiple TNT minecarts on the same segment of rail. I tried doing this, and it doesn't work; I can't place another TNT minecart on the rail once one is already there.

How do I do this?

EDIT: I would like to be able to do this without commands.