The minimum recommended width is 600 mm.
GAP 20 or GAP 40 are probably the best options. Otherwise, a non-cohesive compactible gravel with less than 5% passing the #200 sieve and a particle size of no more than 40 mm may be used.
The minimum embedment is 150 mm. However, it is easier when constructing to use a minimum of 200 mm, which is the height of the Rocklok units. This minimum embedment applies to retaining walls with a total wall height of 1.8 m. For retaining walls over a 1.8 m, the following formula should be used:
𝐸𝑚𝑏𝑒𝑑𝑚𝑒𝑛𝑡 (𝑚) = 𝑇𝑜𝑡𝑎𝑙 𝑤𝑎𝑙𝑙 ℎ𝑒𝑖𝑔ℎ𝑡 (𝑚)/8
For example, the embedment depth of a 3 m high retaining wall would be: 3.0/8 = 0.375 m.
Note: Unless specified by a chartered professional engineer, the embedment depth is to a maximum of 0.6 m (three blocks). Poor soils, toe slopes, or seismically active areas may require extra embedment.
I am building on a slope. Can I use the standard embedment depth?
No. Normally walls built on slopes or with toe slopes require additional buried blocks. It is suggested that the minimum distance between the face of the first Rocklok block and daylight should be at least a 1.5 m (minimum bench). For example, the necessary embedment of a Rocklok retaining wall with a 3H:1V (Run:Rise) slope in front of the wall would require 0.5 m (2.5 blocks).