chuī shā zuò fàn
煮沙子作饭。比喻徒劳无功,白费力气
唐 顾况《行路难》诗:“君不见担雪塞井徒用力,炊沙作饭岂堪吃?”
炊沙作饭连动式;作谓语;比喻徒劳无功。
cook sand for meal--make futile efforts