A typical homesteader root cellar in my area was a roof over a pit with no wall shoring. Most modern designs would have me pouring concrete footings and building concrete block walls and a poured concrete roof.
I have a real scarcity of time and resources to put into the root cellar, but then if i kill myself with a cave in it doesn't really matter if i come in on time under budget..
The sub soil is clay with a bit of sand and it's holding together pretty darn well, so I think I am going to go pioneer style here. Does anyone know if there any plasters or plaster over mesh coatings that I could use to keep the walls from spalling and perhaps confer a bit of stability?
FYI, I will set in two or three posts (trunks) down the midline to carry a log girder down the midline from end to end, then spike smaller log 'rafters' to it for a very low pitch gable (ends resting on earth)...old mill shorts for board roof, tar paper, poly sheet and a few feet of dirt, access from doubled (stacked) insulated hatches in roof opening to ladder, total depth is close to nine feet, my frost line can get to eight feet here. Grade is pretty much level and it's on a high spot in the landscape.