This is the best I can do for pics to describe what I am talking about WS, when you break through the crust you are done, twice on this field an 18.4x38 couldn't reach bottom. You can't work things back and forth it turns into goo and just keeps getting deeper, here the best thing to do is stop and get twice the weight of what ever is stuck, (as in two trucks or tractors equal to the weight of the stuck one) hooked on and pull it out the first try. You never know here when you are going to break through until ya do, I kept all my tires out of the ruts from this 1/3 of a load and chopped the next ten full loads without issue on this side of the field.
The clay here will stick double ring tractor chains to the tires and take away their bite we haven't found any tire that won't load up with it. Truck tires bias or radial are a joke in comparison to double ring tire chains on a tractor.