Repairing or replacing a concrete sidewalk
If one slab has cracked and the slabs beside it still sit flat, replacing that slab back to its joints is usually enough. When several sections have sunk or tipped, the ground under them has usually moved or washed out, and new concrete poured on the same soil tends to go the same way. In that case I'd rather take out the run and rebuild the base, and on a street-side walk the city's inspection settles how much comes out.

