https://en.wikipedia.org/wiki/Shotcrete
https://www.geostabilization.com/technology/shotcrete-robot/
https://dawinvehicles.en.made-in-china.com/product/jBMnaOKdL...
When you deploy a structure like a retaining wall you want to try and ensure that the materials you use will retain their properties as long as possible and if part of it fails, it should not case the whole structure to fail. Add additional design requirements as you like eg colour and texture but always think about function first or you will regret it later!
In a garden setting, you will want to consider: gabions, drystone walling and "sleepers" (large lumps of wood - like railway sleepers).
Some quick material thoughts: Wood is prone to rotting, so ensure it is treated and well drained. Drystone walling can be prone to collapse unless it is allowed to drain properly and plants/weeds should be removed. It should be slanted at around 5 degrees from vertical to resist collapse. Gabions made of galvanized steel wire are extremely strong and resistant to pretty much anything. Devon Popples are an ideal filling for gabions and make a phenomenal structure.
I built a deck part way down in my garden. It is about 5m wide and sticks out about 1.8m. Behind it is a sleeper retaining wall which is about 1.8m high. I angled it back by about 2 degrees from vertical. I laid it on a concrete strip to spread the load and gravel base and back filled with quite a lot of scrap brick and rubbish for drainage. I used some 2m x 10mm stainless steel threaded rods embedded into the conc base to ensure horizontal stability (horizontal shear). I used 180mm, No. 10 passivated screws to keep the wall together whilst I built it and back filled.
"Where can we read more on this engineering"
It's everywhere but you will have to deal with local conditions. I am not convinced you are what you claim.
This makes it much harder for the wall to fall outward as it shifts.
My garden walls are of blue lias which is a bit like slate (https://en.wikipedia.org/wiki/Blue_Lias) it lends itself to flat 1-6" thick blocks that lay into quite neat horizontal rows whilst still being disjoint and allowing water to flow out. Weeds do grow in the cracks and the woody ones at least should be removed.
As you say a thicker wall will be more stable. Water and soil pressure will be most intense at the base, so make the base thicker and thin out as you move up. A slight deviation from vertical will allow for the soil expanding. For example my walls were rebuilt after a dry spell so a few degrees off vertical allows for the clay to absorb water and expand.
Knowing where to look without colleagues or steeping in the field is difficult. When teaching people to code, I often run into the same issue: assuming people are good at googling, or know what Stack Overflow is.
I will even pay subject matter experts when necessary to bootstrap the research and autodidact process. There is no speed limit when learning, but rails and direction have value until you have enough foundation in a domain. I will absolutely let someone teach if they’re willing to set me on the right path, one of the reasons this forum is so valuable: highly knowledgeable people willing to bestow knowledge for free. And asking is mostly free (assuming you are polite and receptive).
Also: Wisdom. It is the difference between knowledge and experience. -Data, Star Trek
You could stop water draining through the retaining wall and turn it into a dam, which will not end well.
My back garden/yard has a 40m drop to a lawn. The levels are managed by dry stone walls. Soil here is heavy clay with really heavy clay sub soil, so efficient drainage is imperative.
As well as drystone walls, consider gabions which can form phenomenally tough retaining walls. You can plant on them too rather than having to weed drystone walls. Gabions are much more resistant to plants forcing joints apart than drystone walls.
Not replacing humans, to be clear, but helping them build better with less effort. Thank you for indulging me. I hope to eventually leave tech to build things that are needed that are built to last (I too am getting old fast).
The important thing with gabion is to realize that they still need careful planning, anchoring, leveling and possibly a foundation to ensure that they aren't going to shift over time.
Which is why gravel backfill with a perforated pipe at the base (that drains to day light) is specified by many/most building codes.
I'm starting to see the advantages of this dry stone wall technique.
They use shotcrete a lot here in BC where cliffs are close to the road, but usually when it's soil or more loose material. Any rock structures (natural or man made) are typically left bare.
Gabion baskets are likely a better idea if you have stability problems and want to do a similar kind of automation.
And depending on the "skill" of the robot and its algorithms, it could be very stable. I know that quite some ancient buildings in south america are put together just with stones put together(with precision and shaping of stones). They survived earthquakes and are still standing. So if enough stones of various shapes are avaiable - you won't need concrete. The weight and friction will hold them together.