Conduit Underground - Ways for tunneling under obstructions?

I'm running into a situation where it's increasingly difficult to bury this PVC underground 18" in some spots due to massive tree roots. Changing directions and/or destroying the roots isn't an option. The isolated roots are easy enough to tunnel under but there are root 'clusters' that are close together are the hard part. I did bore a hole in those roots about 9" deep and wanted to use rigid metal conduit, however the size I need to use (1.25") makes it difficult to source (rent, not purchase) a conduit bender capable of bending this size. I read in the NEC table 300.5 that PVC is under 2" of 'concrete or equivalent' than it can be as close as 12" from grade. My question is: What is 'equivalent'? Also, I tried the 'pressure water' method for tunneling, it got real messy real fast and my pipe didn't stay level, probably doing it wrong. Looking at a few tools such as Borit as a next resort (something cheaper is ideal b/c I'll probably only use it once and I never quite get around to reselling a tool), and calling someone to finish this short portion of trench as a final resort. If anyone can offer insight as to either finishing this trench at 18", or having the PVC above that with 2" concrete (or equivalent?) Also, one idea I just had is running the PVC and forming concrete outside the trench, and dropping it in the trench after it's hardened, hopefully that makes sense. Update Tomorrow (Weather contingent) I will try shop vac'ing around the roots, OP's yard in that video appears to have some root clusters and it looks like he did an excellent job getting the dirt from around them. Patience I have, money I don't. The difficult can be done right away, the impossible takes a little longer.

A worthy challenge for sure. Is there an alternate route that would work better for trenching or boring? Like along the edge of the property, even if it is four times longer than going through the trees.

nope, it's in the backyard, and the tree covers most of it, so no matter the direction from house to garage I'm pretty certain I'll run into the same problem :(