I have a large yukka plant outside the roots of which are forcing concret paving to rise up. We tried to kill the plant about 6 years ago but despite strong chemical it has re-emerged even more vigorously! We need to deal with it as it is very close to the house and is causing a lot of damage.
My farmer dad's solution: 1) saw off your tree so you have a stump. 2) bore holes in the cut trunk with a drill 3) Pour creosote down the holes - this kills the roots. If it isn't thick enough for this, try spraying with Roundup - strong, but biodegradeable.