This does not apply to the NEC, due to it is low voltage, not high voltage being placed in the ground. It should be "Flooded" coax, even if it is a aerial run to the house.
Flooded stands up better to the weather, but the gel is a PITA to get off your hands and the cable.
Really if the ground is soft enough, the OP just needs to slit at least a 4" deep area min,to place the cable in the ground. This is where a Pick-Axe really comes in handy, so you can just place in the ground, then drag to create the trench to place the cable in, then you just put the dirt back over it.
Only art that applies under the NECand IEEE std 1100, is location near high voltage and grounding.