Four years ago I laid a new sidewalk, new pavers in sand.  Before
laying the pavers, I dug a trench a few inches deep down the middle of
the sand, for its entire 60' length.  Poured about two gallons of
castor oil (supposedly repels moles) in that trench.  Waited for it to
be absorbed.  Smoothed over the sand and placed the pavers.  Since then
there hasn't been a single paver heaved up by moles.  Unfortunately the
beasties still show up in other areas of the yard, but I don't really
care as long as they don't mess up the sidewalk.  And occasionally
Shadow the cat finds one and plays with it.... <grin>

Castor oil can be had from soapmaking suppliers.  If memory serves I
paid about $80 for a five-gallon bucket.