On a Boeing 737, can the APU, BY ITSELF, provide enough thrust to move the plane while on the ground? There are numerous questions and answers about the ability of an APU to provide enough thrust to maintain flight.  In contrast, my question is whether the APU, by itself, provides enough thrust to move the plane on the ground.  This is what motivates this question --
Back in the 1980s I often flew between Bangkok Thailand and Chiang Mai.  It was normally a non-stop.  But on one particular flight, it made a stop at a tiny intermediate airport.  Looking out out the window (passenger window) I saw that the vehicle parking lot abutted the tarmac with no intervening separator.  The parking lot was graveled, and considerable gravel had migrated to the area around the plane.
This seemed to me to be a serious safety hazard for ingestion into the engines, and I wondered whether the APU, by itself, could produce enough thrust to move the plane clear of the gravel.
Thanks.
I can't reference to a document, but I can say with reasonable certainty that the answer is no, because like any turboprop or turboshaft, the APU has nearly all of the energy of its mass flow extracted for bleed air, or for torque production purposes for electricity, so that there is little thrust energy available.  Turboprops typically get maybe 10% of the total energy available from the engine as exhaust thrust.
So using that number for an APU in an airplane the size of a 737 that is making, say, 650 shaft horsepower (just an educated guess; the actual number is surprisingly hard to find), it's producing a thrust equivalent to roughly 65 hp statically out its tailpipe, which equates to perhaps 2-300 lbs of static thrust (I recall that it's something like 4lbs thrust = 1 HP in the static case) at most.  That would be if the tailpipe was even optimized for making thrust in the first place (tapered to accelerate the flow), which they are generally not.
So, figure on a few hundred pounds of push at most, probably quite a bit less, which isn't going to move a 737 unless it's on some kind of near-frictionless surface, or in outer space.