Good philosophical mind-teaser, aye?
um the bulldozer would pass through the wall. there is space between the cells of the wall and the partials of the bulldozer would pass through the wall's spaces.
If the bulldozer truly couldn't be stoped (a near impossibility but ill go with it theoretically), and the wall truly couldn't be moved, (again we will have to suspend logic to solve this one) then either there would be a paradox of physics resulting in some sort of fusion, or both would cease to be, and in their place would be a smashed wall that could be moved, and a broken bulldozer that could stop.
Simple. The bulldozer that couldn't be stopped can Now be stopped by the wall that can not be moved. Thanks for asking
ZAP!! That was the sound of the Laws of Physics being disintegrated in an instant. I can see the sparks flying all over the place and the world as we know it come to an end I can see the bulldozer still moving and the wall still standing - even though they are in full contact with each other. I can see all this because I am floating against gravity above it all.
It would burn out and rust because the wall isn't going anywhere. The wall could only be removed if the bulldozer really wanted it too, but the bulldozer would only hit another wall. So this is how some journey's go, some will ultimately burn out and rust because they cannot move beyond the wall. The bulldozer could lift itself up over the wall too if it is smart.
