Bring pineapple juice to a boil in a small sauce pan. Pour in gelatin, stirring 2 minutes or until completely dissolved. Transfer mixture to a bowl and chill in the refrigerator until thickened to the consistency of egg whites.
Meanwhile, line the bottom and sides of an 8-1/2 inch springform pan with vanilla wafer cookies.
Reserve 1/3 cup mandarin oranges for garnish; set aside. Combine gelatin and yogurt and stir until completely blended. Fold in whipped topping. Gently fold in remaining mandarin oranges.
Pour mixture into prepared pan. Cover and chill for at least 3 hours.
Set pan on serving plate and remove pan sides. Garnish with reserved mandarin oranges.