"ringed wall of whirling blades with a radius of up to 5 ft. per two levels"
So, at CL12, you can get a 30' radius ring. Which would mean a 60' hole in the middle. Of course you can reduce this down to a 5' radius, which would leave 1 square in the middle open for you to stand in. You can't make the wall thicker however.
In short, yes you can make a ring around you, but you can't make it triple thick.
Wall of lava, supression, stone and thorns all have (S) in their area.
From the magic section: "(S) Shapeable: If an area or effect entry ends with “(S),” you can shape the spell. A shaped effect or area can have no dimension smaller than 10 feet. Many effects or areas are given as cubes to make it easy to model irregular shapes. Three-dimensional volumes are most often needed to define aerial or underwater effects and areas."
Because blade barrier is lacking the shapeable modifier, I would argue you can chose between straight line wall, or ringed wall as described in the spell.
I do see an argument that all walls aren't straight, and it isn't explicit (like some other spells are), so RAW is not clear. My point is RAI I believe to be straight line walls or rings.