Using concrete blocks as part of climbing frame footing

[UnusualCapybara]

I'm building a 3.5M tall climbing frame / zip wire platform in the garden and want to make sure the legs are well secured particularly given the height and leverage.

I have a lot of very heavy concrete blocks from a demolished outbuilding, would it be practical to dig a larger hole, throw in a bunch of these around the post and pour concrete over the lot? My thinking was that the concrete would glue the whole heavy mass together and create more resistance with less concrete used than just filling the hole directly with it.

 

[freddiemercurystwin]

Wouldn't the hole need to be enormous to allow you to throw in a 'bunch' of concrete blocks as well as some concrete?

 

[UnusualCapybara]

Renting a mini digger for a weekend for a bunch of garden projects so a large hole is entirely possible! If this were a dig by hand job, I'd absolutely not be considering it

Edited to say: The blocks are really dense - 30kg of weight from a block measuring 44x20x13 so seemed to offer a lot of weight benefit for the given space taken up.

 

[Deluks]

At that height, the biggest load on the structure would probably be wind, rather than people actually using the frame. Don't skimp on the depth.
A solid single poured concrete mass will be stronger than poured concrete with loads of big lumpy bits in it.
You'd be better off trying to lay them as blocks, interlocking with a bond, preferably with rebar, rather than just chucking them in a hole.

 

[scbk]

I would keep the concrete blocks for something else and dig as narrow and deep post hole as you can

 

[SFK]

Looking at my tall wood fence posts - whose wood has shrunk in their concrete foundations making them move a little, and being worried about rot at the foundation/air point - would you better using some steel 'I beams' as the uprights?
eg, randomly found using google to show price examples, www.steelbeamsdirect.com
SFK

 

[big-all]

a zip wire 10ft up is a heck off a lot off leverage unless its well braced to hold the load??
do have any close neighbours and what are there thoughts
if you have a platform above 300mm that you can dwell on it may be subject to planning ??

 

[UnusualCapybara]

a zip wire 10ft up is a heck off a lot off leverage unless its well braced to hold the load??
do have any close neighbours and what are there thoughts
if you have a platform above 300mm that you can dwell on it may be subject to planning ??

I should have been more clear - the zip wire is braced between two big trees, the platform is a launch point rather than bracing the wire. We don't have any particularly close neighbours but it's a good point about keeping any 'dwelling' below 3m.

 

[Alastairreid]

it's a good point about keeping any 'dwelling' below 3m.

300mm.