Bruce...the angle will depend on the gradation, but for a typical crushed concrete gradation (Nominal 2" down to fines), the angle would likely be in the 35-40 degree range.

Thanks for your comment, Ron.  I'm specifying 150mm down (max. size) for the demolition concrete, so it would be closer to the 35 degrees, than the 40.

On top of the concrete fill, we're planning to stack coal, which will be more like the 50mm down you mentioned.  I could probably use 40 degrees for that material.

I practice as a 'sole trader', and its good to get some feed back on these sorts of issues.  I don't have the opportunity to discuss things over a morning coffee, like when I worked for a larger practice.

Thanks again.

Best wishes for Christmas

Bruce

Bruce,
I know the feeling.  I've been in your position myself.  Now back in corporate life after being a single practitioner, building small practice, and then got "absorbed" by one of the larger firms.   There is a great benefit (as well as a warm, fuzzy feeling) when you have someone to bounce things with.  These forums are a great place to do that.  You'll find everything from blithering idiots to some of the most knowledgeable engineers in the world...but the beauty of the system is that the peer review process weeds out the bad answers and you get left with some pretty credible info to work with.

OK...two dangling participles in one post...I'd better watch out for the grammar police.

Anyway, good luck in your practice and be a frequent visitor here.  You'll enjoy it....you'll get back at least as much as you give.

Have a great holiday!
Ron