Part of my father's driveway is sinking. The house is about 35 years
old and it's the original concrete. A large crack happened several years
ago but my father didnt notice the sinking until recently. The driveway
concrete is on an angle (going up hill to the parking pad next to his
house). When it rains, there is dirt wash out at the bottom of the
driveway so I suspect the crack is taking the rain water and directing
it under the sunken portion of the driveway and that is flushing the
dirt out from under the area below.

Obviously, we need to seal the crack but with such a large gap there,
I'm not sure what to use. Any suggestions would be greatly appreciated.
My father has no money whatsoever so we're trying to do this as
affordable as possible for him. I was thinking about using some
hydraulic concrete filler but I'm not sure if that is the right type of
application for it.

The next question is whether the slab could be lifted up and fixed or
would it have to be completely removed and re-poured (something that
none of us have the money to do).

Thanks