Sounds like you need to create a throwing lane...like in horse shoes. Dig up a 4 foot by 4 foot square about 4 inches deep and fill it with dead sand. Stand target target on tripod stand...well you get the picture.
Hey! I googled ax throwing rules and got http://www.inquiry.net/outdoor/skills/axe/axe_throwing.htm
Isn't the internet great!
Bob