A floor can't collapse unless there is a cavity below it for it to collapse into, but it can be cut downwards by the cave's stream.
It is called weathering.
I'm not really sure what you had in mind. Given that the cave is in limestone (as the vast majority of them are) there has to be a dimensional limit to the dissolution and erosion processes. The floor is there by default: it is the lowest surface along a passage at that given time in the cave's development.
A Boulder, or Talus, Cave is simply an enterable void or set of voids between boulders and the rock-face from which they have fallen. Collapses within existing karst, sea or lava caves may choke the passage or chamber with boulders, and such chambers are often called "boulder chambers", but that does not form the cave, and it is not the same as a true boulder cave.
A Boulder, or Talus Cave rather stretches the definition of "cave", but it's simply a void or set of voids left between fallen boulders and their source rock-face. A cave's chamber that is heavily obstructed or even terminated by collapsed rock is often called a "boulder chamber", but it's not correct to say that collapses form caves. They don't - they modify them.
A basement A bunker A cellar A cave A cavern
When rock above a cave collapses, a sinkhole is formed.
It is called weathering.
It is called weathering.
A sinkhole.
When the rock above a cave collapses, it can form a sinkhole if the collapse creates a depression in the ground. This can sometimes lead to the formation of a sinkhole cave system underground.
It is a sink hole if it reaches the surface.
You run for your life ;)
Shakehole or Sinkhole - when the collapse extends to the surface. (Not all cave roof collapses disturb the surface above.)
It is called weathering.
When rock above a cave collapses, a sinkhole is formed.
A sinkhole is formed when the roof of a cave collapses.
It is called weathering.