Catch the edge with 10/10 squared timber

Hi, we have several elevations on our property. Unfortunately, the lowest part is now very difficult to reach with machines, so everything must be carried there and installed by muscle power. Approximately 120 (high) already existing embankment made of stable (so it doesn’t fully slip on its own) but muddy stone/mussel limestone/mud/clay should be retained. The plateau is only walked on, so no additional load from cars or such. I have ordered steel H-beams and will concrete them in. Into the recesses of the beams, I want to push 10/10 squared timber (I have tons left over from construction) from above. Against the slope, there will be a studded membrane and drainage gravel and possibly a drainage pipe. I think that will hold. What I don’t know is whether I can stack the timbers (all untreated, and I can’t paint them now given the weather) directly on top of each other or if it would be better to use spacers (e.g., nuts) to allow some ventilation?!? Then, of course, the studded membrane must never break, otherwise all the gunk will run straight through.... I’m just concerned that if the timbers are stacked directly on top of each other, the whole wall might rot?!?
Best regards

That will happen anyway if the wood is normal spruce / fir, whether with or without Noppenbahn. Only the timing shifts.

I basically think "Abfallholz" upcycling is a good idea, but in my opinion it won't be enough here.

You would have to take the nasty oil-soaked old railroad ties that were often used outdoors decades ago. They last longer, but not forever either.
Or expensive tropical wood (or is there something local?) that is suitable for such applications.

Planting the slope so that it is well root-penetrated is always a good option, but probably not enough and takes too long here.

You see, your solution is possible, but not permanent .... I'm also not a fan of L-stones, but I think they would be appropriate here. Also to better absorb the earth pressure than (how deep?) concreted-in T-beams.

I once built something similar, using so-called planting stones to build "towers" about 1m high and then filled them with concrete. Then I placed construction planks behind them, three stacked on top of each other, just like you probably want to stack your wooden beams now. To prevent the soil from coming directly into contact with the wood, I put a kind of roofing felt between the soil and the wood, and it has held up until today, almost 20 years. I had taken pressure-treated construction planks, but to be honest, it probably wouldn't have mattered. I would do it the same way if I were you, and if at some point a spot rots, you can just repair it there or eventually use a different material as a protective wall. Until then, you have several years... The wood is exposed to nature from all sides anyway, so I would save yourself the trouble of painting it; that might only make it last a few months longer :D As simple as possible... I like it!

So there is basically no alternative to my plan... the question was just whether with or without a ventilation gap. But you are probably right: it doesn't really help or not much. I have tons of construction timber, formwork panels, etc. left over and that has to be used; the last wood container cost 500 euros and was just a drop in the ocean... so the rule is: use it (treehouse, fence, raised beds—those are already taken care of), burn it, give it away... I can't fit L-shaped stones there, nor bricks, hollow blocks, the huge amount of concrete for foundations... everything has to go there and be carried underneath: that's not possible (at least not without numerous "victims" carrying it for days). The steel beams (70-80 cm deep, more is not possible because of the ground) will outlive me and could possibly be fitted with new squared timber later. I hope/think the wood will definitely last 10-15 years?!? The slope behind will gradually compact more and more over time and probably wouldn't give way immediately if the squared timber is replaced.

That's exactly how I see it too. What's better than being able to use your existing material? It's great. If you have too much, you can just lay it double. In a few years, if anything rots away, the slope will be firm anyway (like with me). The steel beams are good too, it's not in the living room after all. I always like such things better than all the expensive DIY store system solutions.

It took a while but now the wall is finished.... I think (hope) it will outlive me.... and I also think it turned out quite nice. Of course it could be better but as I said: all by hand; no heavy machines possible!
Best regards