How do cave ins work?

[Arbor]

I heard you need to build a mine support where the cave in happens but how much time do I have to do that?

What if I dont build a mine support? will rocks fall on my head or the mine be unusable or..?

Does a mining helm protect me from the cave in?




also how safe am I when I mine within the range of only one mine support?

[Telcular]

From what i´ve read/heard, you have 5-10min to build a support before there is a cavein, at which point you take damage (if you are close to the area) , and rubble fills the area so you have to mine it again.
Can´t say how much damage it does, i always make sure to put down supports when the screeching sound starts.