Basalt baseline for slope stabilization?

Hi,

I hope to get an initial assessment from you here on whether my project should be considered critical or if I only need to worry little (or not at all). I understand that a comprehensive consultation requires an expert on site.

Now to the project.
I want to remove some of the slope behind the house to create some flat (=usable) space. Attached are pictures of the slope (3 pieces) and a rough sketch of how it currently is and how I would like to have it excavated. As can be seen in the pictures, the property borders a neighboring property at the top, whose wall must of course not collapse due to this adjustment. The soil is "normal" topsoil, I would say, nothing special. The neighbor's wall is a concrete block wall, cast with concrete, and on a strip foundation made of concrete, approx. 10 cm thick and 50 cm wide.

I want to retain the slope then with basalt boulders (since many are already available).

My question: Should my project be considered critical, or do I not need to worry here? It would be disastrous if the neighbor’s wall were to collapse.

Please provide a brief preliminary assessment based on the attached pictures and my explanation.

Thank you very much and best regards

Simon

Up to 60 degrees you have no problem. I assume that you have crushed basalt stones, which are often called boulders. A low wall would be sufficient, then leave the rest sloped - or build the wall all the way up. What your neighbor did looks pretty awful.

Up to 60 degrees you have no problem. I assume that you have crushed basalt stones, which are often called glacial erratics. A low wall would be sufficient, then leave the rest sloped - or build the wall all the way up. What your neighbor did looks pretty awful.

Yes, correct, I mean crushed basalt stones :-)

Up to 60°? According to my calculation (current state sketch) I unfortunately come up with a 64° slope (please check again if I calculated correctly) :-/

Should I compact gravel separately for the basalt stones, or would it work like this? That would be easier.

I often walk along paths on the bank of a federal waterway, which is lined with loosely wedged basalt, and have the impression of permanently stable path surfaces.