埋头苦干 [- - kǔ ɡàn]work with quiet hard application; bury oneself in work; engage in unostentatious hard work; immerse oneself in hard work; keep one's nose to the grindstone; plug away; quietly immerse oneself in hard work; quietly put one's shoulder to the wheel; work intensely:
•¶ 你那埋头苦干的精神令人尊敬。 Your quiet hard work will command respect.
•¶ 他勤勤恳恳，埋头苦干。 He industriously engages in unostentatious hard work.