If driving over a pile of gravel knocks your car out of alignment, you have a poor car.
I am sure the alignment shop will go through the alignment proceedure for you as many times as you bring the car in.
They make money doing that.
I would bet the car isn’t out of alignment.
It’s not the gravel that knocks it out—it’s the 6+ inch curb that has to be driven over at an angle.