I've thought I would cut off one sidewall of a tire before packing it.
More work, more tools,more efficent, less frustrating?
The best use of tires in an "earthship" I've seen is the compressed tire block.
Made of tires that are baled into a cube, they are so heavy and dense it is said they can be used to build a wall directly on the ground without footers!
There is a thread here on Permies by an owner/builder.
Regarding other ways to build with soil, soil concrete is something I would consider, but
RapidAdobe is what I really want to try:
http://velacreations.com/howto/rapidobe-walls/
Basically rammed earth in leave in place fabric forms.
Very diy friendly in terms of labor and material resources.
Velacreations post here under a different name, and thus is only one of their great contributions.