function digColumn()
	turtle.dig()
	turtle.forward()
	turtle.digUp()
	turtle.digDown()
end

function digTunnelPart()
	digColumn()
	turtle.turnRight()
	digColumn()
	turtle.back()
	for i = 1, 2 do
		turtle.turnLeft()
	end
	digColumn()
	turtle.back()
	turtle.turnRight()
end

function digTunnelSection()
	for i = 1, 4 do
		digTunnelPart()
	end
	turtle.turnRight()
	for i = 1, 11 do
		digTunnelPart()
	end
	for i = 1, 11 do
		turtle.back()
	end
	for i = 1, 2 do
		turtle.turnLeft()
	end
	for i = 1, 11 do
		digTunnelPart()
	end
	for i = 1, 11 do
		turtle.back()
	end
	for i = 1, 2 do
		turtle.turnRight()
	end
	digTunnelPart()
end

digTunnelSection()