Minecraft Turtle Code (untested)

--1x3 Meter Mine Shaft

--Total number of meters the turtle will crawl
print("How long of a tunnel would you like sir?")
print("")
term.write("Shaft Length: ")
x = math.abs(tonumber(io.read()))

while x>0 do
--Detect & Mine for Gravel/Sand falling
  turtle.detect()
  if turtle.detect() == true then
  repeat
    turtle.dig()
    sleep(0.55)
  until turtle.detect() == false
  end

--Move forward, dig up and down, completes row.
  turtle.forward()
  turtle.digUp()
  turtle.digDown()

--Reduce Row Count
  x = x-1
  print(x.." Meters Left Sir!")

end

print("Done sir!")
Fuel = turtle.getFuelLevel()
print("Fuel Remaining: "..Fuel)