Im not sure if this has been said before,
having reinforced concrete block for something like 32mpa in the ground .5 x .5 x 1.0 meter block, followed by leaving 20cm below surface level, and have reo bar coming though from the bottom block. also having threaded rod coming from the bottom concrete block right upto the top of the peir, to tie it all in.
Further more lay a set of bolts into the concrete before finishing it off to mount the Metal peir tube to your liking and somthing like 6mm thick walls to the lower block
Once dryed and tightened up, pour the top 20cm of the block to seal in the peir tube. Once dry fill the peir with fine washed sand and compact, leaving a 20- 30 cm void in which to cap the peir off with 32mpa concrete. all in all it is overkill but hey why do we build a peir.! the idea was from this thred utilizing the sand to suppress vibrations.
Sometimes my ideas seem and look a little bit messy, though in my head they are pristine!
if anybody wants the plans, ill shoot something up in CAD
Brendan