I'm building an Allan Block retaining wall and I'm trying to follow the
manufacturers directions as closely as I can. It's going to replace a
30 year old railroad tie wall that was secured by rebar driven 6 feet
into the ground. I have removed the old wall and have the block and
gravel on site. But I have never used a plate compactor. I had dug the
old wall back just enough to allow me to backfill with 12 inches of
gravel and then compact it. I see now that any plate compactor I can
rent will need more than 12 inches to operate. I'm leaning towards
digging back a few more inches, renting a reversible plate compactor,
and seeing how that goes. But it has also been suggested that I might
get away with using a jumping jack for compaction - much lighter to move
up on each 8 inch course and also narrower. But the description of how
the thing jumps around is putting me off. Any thoughts from anyone who
has used either device would be appreciated!
With the PC it's easier to get a smooth and level surface. The JJ
tends to leave dents the size of its head. But given the extra heavy
work required to use the PC, I'd probably give the JJ a go. It will be
a lot easier to maneuver on the upper courses. After you've got
everything solid, spread a little extra sharp sand on top and screed
it with a long 2by to fill in any low spots. Regardless of which way
you go, wet down the material before you compact it. Provides a
little lubricant so the material compacts better.
I worded that poorly. I meant spread some extra sand and use sharp
sand (mason's sand, not play sand). Generally you want 1/2 an inch to
an inch of sand on top of the base material. It's a lot easier to get
the block positioned even and level with a little sand on top of the
I went with the plate compactor instead of the jumping jack. I have a
Spitzlift that attaches to my old Ford Explorer (sort of a mini crane
with a crank) that I am using to position the plate compactor. Today
was just a test run on the base rock. Tomorrow will be the real thing.
It's not what I would call a fun machine to use but the rock sure seems
a lot more solid after a couple of passes.
Getting the block aligned AND level was much harder for me than I ever
imagined. Without the sand I'm not sure what I would have done. But
now I only have a couple of blocks left to place on the base course and
then I need to compact the stone behind it. I am having a hard time
imagining that the blocks won't shift when I do that. Since they have
soil in front, gravel in the voids, and gravel behind them, I may be
wrong about them shifting, but if they do......................... Got
any advice on that?
I wanted to follow up on this in case someone Googles for 'plate
compactor' some day...........
It may have just been beginners luck, but I had almost zero problems
with the plate compactor moving the Allen Block out of alignment or
level. The project was one hell of a lot of work but I'm quite happy
with the end result.
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