The one annoying thing about Computercraft is that all computers and turtles reset when chunks unload. So I wrote a version of "Excavate" called "Quarry" that saves its relative coordinates to a file and reloads that file if anything happens.

pastebin get LEHQExFi flex.lua
pastebin get eGkHs4Kk dig.lua
pastebin get pEHirhY0 quarry.lua
pastebin get Jkd18h5j stairs.lua

Flex and dig are APIs used by many of my programs; Quarry works just like Excavate, and Stairs will dig a staircase around the excavated area; put a second turtle just to the left of the first and run "stairs <diameter> <elevation(Y on F3)>".