I'm not an expert in this line but my consent used tyres can be used for foundation in many ways. For example constructing road on swampy area by laying all used tyres then buried and covered up with sands or earth on top as foundation purpose. These methods also can be used for construction in your house car poach and factory foot layering before cementing it. My ideas it will avoid sands erosion running away during heavy rain . These maybe a way to cut cost in earth filling too. Second can be used for river side to protect your river band from wave. 😂😂😂😂😂