[Golf1echo]

As Pete said FM5-34, sections 7 and 8, also sec.9 as it has culvert design, expedient surfaces to include Chesaling mat roads and Corduroy details.

Just South of you a bit (WNC) the old timers used alternating logs covered with earth to make small bridges over creeks since they did not have culvert materials. Yellow Locust trees!! would be a good material to use as they will "last longer than the holes you put them in", I suppose a corduroy made with them would be quite workable for horses, tracks and wheels.

You will find metal landing mats in sec.9 too. Depending on your grade, I do not like the metal so well as tracked equipment can slide if not done appropriately.

The USFS will use nonwoven mat material either to take traffic or to allow the vegetation to come back but depending on use it might not be sufficient? If you can get a blast mat (rubber material built into a mat, used for placing over charges) that might do it but would possibly be detrimental to water quality?

Below is a picture of a concrete/rock surface seen in the Cherokee Indian Village, it is probably a third the dimensions you mentioned and I would arrange to rocks differently or not use them at all for the uses you mentioned ( Possibly use wire reinforcements in about a 6" slab unless you expect heavy traffic.)
Edit: 2nd image is an example of what TR said, when water did come it took the stone with it. ( Greenway trail )