How do you always have a chunk loaded in Minecraft?
The command: setworldspawn <x> <y> <z> . Although spawn chunks are usually kept loaded at all times, new spawn chunks won't be loaded by this command until a player moves within range.
How do you stop a mining turtle?
Yes, this is standard behavior of turtles. Unless you give them a chunk loader – they will stop working when you leave them. And if you're playing singleplayer – they will always stop when you exit your game.
Does the buildcraft quarry load chunks?
Yes a quarry will always keep chunks loaded where ever you are in the overworld. The quarry will also stay loaded if you are not on minecraft only if you are on a server that is constantly running.