I have a retaining wall as in the diagram. It's 750mm high excluding coping and 440mm wide at the base. A 100mm perforated drain runs along the bottom.
So far, the 20mm washed gravel I'm using has reached 550mm from the bottom of the wall (NB the bottom of the wall is 200mm below ground level - see diagram). It's taken 4 tons (4 bulk bags) of gravel to achieve this, which I have to manually bring into my garden up 25 steps from the road, 2 buckets at a time.
My question is, do I need to go higher? Another ton will get me another 100mm. Or can I now get on with replacing the excavated material.
NB, the gravel is inside a geotextile membrane and the pipe is inside a geotextile sock).
I would say gravel needs to come to the top. Maybe not the full width. Shutter it with the back fill material leaving you with a 100 mm gap to fill.
Shutter, gravel, shutter, gravel etc
Ideally, the gravel should come up to surface level, but, if it's killing you, wrap the geo-textile over the top of the gravel as it is at the moment, and cover with soil. 200mm or so of soil cover won't be too much of an issue.
