ᐅ Basalt rock line for slope stabilization?

Hi,

I’m hoping to get an initial assessment here on whether my project should be considered critical or if I don’t need to worry much (or at all). I understand that a full consultation requires a professional on site.

Now, about the project.
I want to cut back the slope behind the house slightly to create some flat (= usable) area. Attached are three photos of the slope and a rough sketch showing the current situation and how I would like the excavation to be done. As shown in the pictures, the property borders a neighboring plot at the top, and the neighbor’s wall must not settle or shift due to this adjustment. The soil is what I would call "normal" topsoil, nothing special. The neighbor’s wall is made of concrete masonry units, poured with concrete and built on a continuous concrete footing approximately 10cm (4 inches) thick and 50cm (20 inches) wide.

I plan to retain the slope using basalt boulders (since I already have many available).

My question: Should I consider my plan critical, or is there no real need to worry here? It would be disastrous if the neighbor’s wall settled.

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

Thank you very much and best regards

Simon

Up to 60 degrees, you shouldn’t have any problems. I assume you have crushed basalt stones, which are often called boulders. A low retaining wall would be sufficient, then you can slope the rest - or you could build the wall all the way up. What your neighbor did looks quite unpleasant.

hampshire schrieb:

Up to 60 degrees you shouldn’t have any problems. I assume you have crushed basalt stones, which are often called glacial erratics. A low retaining wall would be enough, then you can slope the rest – or build the wall all the way up. What your neighbor did looks quite rough.

Yes, that’s correct, I mean crushed basalt stones :-)

Up to 60°? According to my calculation (existing condition sketch), I actually get a slope of 64° (please double-check if I calculated correctly) :-/

Should I compact gravel specifically for the basalt stones, or would it work without that? It would be easier that way.

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

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