Earthship on the beach, sand soil

Dear All,

I am in the process of building a house and my problem is, the lot is 2 blocks from the beach, the soild is sand, sand and sand, in the summer I dug a whole 6 feed/2 meters deep and everything was sand than water. There are a lot of houses here and they use a flat reinforced concrete platform to build the house on top of it. If there is not another idea I will do it too, and the South wall will be tires filled with sand, dust and clay (which I will have to bring to the site).

I tried to fill tire with sand but it does not work very well.

I will be glad to provide more info. but mainly I would love to read your thoughts.

thanks,

Carlos from Uruguay.