I’m curious why you want to pump concrete behind the wall as that isn’t going to solve your pressure problem against the wall.
Thanks. We don't want concrete, but had thoughts that was all we may be able to pump in.
Between the pool fence built on top of the retaining wall and the boundary fence to the rear neighbours is only 500mm.
The land is in the old Brissie suburbs and only 10 metre wide. By the time a house goes up there is no room to get any plant to the rear that could reach far enough to place fill.
cheers