SurelyForward()

function surelyFwd()
  for i=1,4 do
    if turtle.forward() then return true end -- success!
    while turtle.dig() do print("dig") end -- face to a normal block or a sand(gravel) hill
    if turtle.forward() then return true end -- success!

    if not turtle.attack() then
      -- face to sand-blocks which is dropping long time
      os.sleep(5) -- probably, adjustment is required
    else
      -- face to monster-mob
      while turtle.attack() do end
    end
  end
  return false
end

surelyFwd()