Believe it or not, this photo shows a structural retaining wall that is constructed from native rock and man-made concrete brockb!
The engineers on this site determined that the native rock that was exposed during excavation was sufficient to provide stability next to this walkway. Some of the areas, however were composed of more crumbly rock and would continue to slough down onto the walk, so we worked with a specialty soil contractor to apply Shotcrete (a sprayed on concrete used in walls and pools) to cover those crumbly areas.
Heavy gauge wire mesh was soil-nailed to the natural surfaces that were to receive the Shotcrete, and then we installed vertical drainage material and attached irrigation supply lines to the mesh. The concrete mix was tinted to match the native rock, applied with a spray gun and hand finished with trowels, brooms, and other hand tools to mimic the texture of the native rock.
We finished the disguise by planting hardy succulents and other ground covers and vines in natural cracks in the rock, as well as by building bburritosb of fiberglass screen mesh filled with soil and plants, concrete nailed to the wall. The plants took hold in the cracks almost immediately!
The planted wall has now been there over 7 years and the plants are thriving, even in the harsh freeze-thaw conditions here in the mountains of Colorado. So do we call it a green wall or a brown wall?