Thanks for the responses so far.
The wall is 1400 high and 10 metres wide and has around a 500mm to 900mm gap at the top so it would need around 10 cubic metres + any compaction.
The wall is on a proper footing, blockfilled, reinforced, waterproofed and has aggie drain behind it, so I am not overly concerned about the material used and only suggested wet sand as a medium a concrete pump might handle.
I would rather use dry road base/gravel etc but getting a dry mix into place looks more difficult.
The trouble is it is 40 metres back off the road up a 15 deg slope, and a house blocks all but a 3 metre wide access. In Brisbane I think I'd be spending more time at friends funerals than getting the work done by hand
A conveyor may work, but it would have to be 40 metres long and then flexible enough to not need barrows.
Cheers
Ian