tunnelSM

function tunnel(depth)

    local function refuel()
        if turtle.getFuelLevel() < 100 then
            turtle.select(1)
            turtle.refuel(2)
            print("Refueled")
        end
    end

    local function checkFull()
        if turtle.getItemCount(16) > 0 then
            turtle.back()
            turtle.digDown()
            turtle.select(2)
            turtle.placeDown()
            for i = 3, 16 do
                turtle.select(i)
                turtle.dropDown()
            end
            turtle.select(3)
            turtle.forward()
        end
    end

    local function forcePlace()
        turtle.back()
        turtle.digDown()
        turtle.select(2)
        turtle.placeDown()
        turtle.forward()
    end

    local function mine()
        while turtle.detect() do
            turtle.dig()
            sleep(0.5)
        end
        turtle.forward()
        while turtle.detectUp() do
            turtle.digUp()
            sleep(0.5)
        end
    end

    for depth_count = 1, depth do
        refuel()
        checkFull()
        mine()
    end
    forcePlace()

end