"앞만 보는 불도저"
=> (literally) A bulldozer(불도저) that only(만) faces(보는) forward (앞)
=> A bulldozer that only goes forward / A bulldozer that only knows to go forward.
It is a phrase describing someone who works toward his goal like a bulldozer never tiring or changing course, overcoming what gets in the way.
But from what I've seen, it is more common to say 앞만 보고 가는/전진하는/달리는 불도저.