This will work for dry clay, another good reason for locating your shelter at the top of a hill in addiation to the geometry for radiation. Try to have a well in the main part of the shelter with full casing, lockable cover, and concrete around the top of the casing to prevent contamination. Seed earth with grasses and small plants native to region to hold earth, not attract attention, and for food for game. You will have to fertilize since the earth will be partially clay. You will have to have low spots in the roof in the dog-legs of the tunnel due to the backhoe not being able to make really sharp corners.
Plant bushes around end of tunnel.
Service, Layfayette,IND 47907. You need a strong shelter manager to enforce rules and rations. Don't waste your ventilation on fires for cooking, use sand as a fire extingusher.