Currently the only way to remove paving from cave floors is by using "Digging" This means you have to go for tile after tile and remove them one by one, in a really tedious way.
By using Stomp to dirt, you can select an area and remove it easily.
If the problem is that its name is: stomp to "dirt"
I Suggest renaming it to something like "stomp land" or adding an extra terrain modifier that is the same but for cave floors.
Thank you.