Batch box for yurt with concrete drainpipe bell

So some good friends of mine want to build on their land in the dry interior of Central Otago, and just got engineering estimates for earthworks in the range of half a million dollars. <gulp> They are now considering putting a large yurt on the property so that they can live on site and peck away at the permanent house and try to make it fit their budget. They really like the little J-tube RMH i have in my glasshouse and are pretty serious about having me help them build a 6" batch box for the yurt.

I explained the merits of bells or stratification benches in this type of design and now we're considering using concrete drainpipe sections sawn in half lengthwise, maybe with cob on top for levelling the bench. Has anyone done this? It seems intuitively sound. The motivation is to have something that goes up and eventually comes down fairly easily. I was thinking 600 mm diameter pipe on a brick or fieldstone stemwall (their land is practically a schist quarry and the rocks naturally split into rectangular-ish blocks).

Hi Phil;
This sounds like a fine bench-building material, along the lines of Matt Walker's 1/2 barrel build.
600mm, wide bench with a tall brick bell to contain the core should be plenty to keep a yurt toasty.

Sounds faster and easier than pouring a structural bell.