The paver had come up against the sidewalk
Does it mean that the paver was pushed up vertically?
One meaning for when something is up against another thing is that it is pressed firmly onto it. (In the link, "up against something," definition 1.)
This is particularly true when the two objects involved are inanimate. If one or both is a living thing, particularly a sentient living thing, then the phrase tends to indicate a conflict instead of simply being closely adjacent.