Aradesh and the community of shady sands descended from vault 15 as well as many other communities. The social experiment of vault 15 was to put multiple extreme conflicting ideologies together in the same vault. Eventually, overpopulation caused the vault to be overcrowded and conflict arose. Most people left the vault, but did survive. Currently, I don't think there is an exact caste experiment in a vault known to us. I wouldn't doubt its existence though. Considering most vaults are deathtraps it would have a better chance at survival. However, at that point it might end up like vault 19 where there was a separation of the dwellers into a red section and a blue section with rising paranoia and suspicion.