2m High, 18m Long Retaining Wall

[StirlingQR]

Hello there!

I am looking to redo our garden, this multi level retaining wall is crumbling away, tiered over 2 levels. I want to dig out the bottom "flower bed" to have more flat ground there, and then rebuild the wall to where the top level is, but build it higher to upto 3m total (can be less, like 1.6/1.8m).

I will dig out the bottom level, keep most of it and dump it at the top level to level it out later, then muck all away - no issue.

My issue is with the actual wall itself. The steps down down ends of the garden will come out and the wall will run all the way down to the far side to the trees, about 18m - then with steps in the middle of the wall to the top (somehow). My issue is HOW TO BUILD THE WALL?!?!

My options and thoughts so far:

1) Concrete blocks, rebar, with with concrete, PDM, corregated pipe for drainage etc
2) H shape "RSJ" buried 1m deep - using as fence posts - then use either sleepers OR gravel boards in between to create a solid "fence"
3) Gabion wall

Looking for advice for most cost efficient, the finish, practicality of doing 95% of the work myself (not outsourced all to a landscaper for example), or other ideas to look at.

Any thoughts on this length and height retaining wall?

 

[freddiemercurystwin]

Needs a structural engineer really for a beast like that, probably block work if purely DIYing, walls will be pretty thick (rule of thumb for retaining walls is the thickness at the base should be about 1/3 of the height) so about 600 or 3 block wide at the base.