there are various earlier, and perhaps current designs for grass strips, where differnt species mixes, and work are prescribed for different zones, as the ends of the runnways where landings occur can be reenforced, but taxi and take off runns can be less heavy duty. agricultural colleges were(are?) tasked with this sort of thing. we have a very large formerly paved airport localy, that has gone back to grass all by itself, and is now mowed, but it generaly only sees light planes, but the underlying gravel bed and drainage systems are still intact, and so could be used for landing a heavy jet in an emergency, but with a number of 9000' paved runways quite close, that has not happened yet. in any case,the load bearing capacity of different soils and terains is quite well understood, and heavy jets have emergency landed in crop fields unharmed, and then been flown out after some modest preperations