I'm going to box out an area of around 7x10m using 200x75mm sleepers, single height. 100mm of these sleepers will be on or just below ground, the other 100mm will be filled with compacted crushed rock.
I plan on using https://meetjack.com.au/product/retain-it-heavy-duty-retaining-stakes/ on the joins and 1 on each of the corners. To give a little more strength, I also intend on pinning the sleepers to the ground using 600x12mm deformed reo right through the sleeper at or about 1000mm apart.
https://imgur.com/a/EjY4muF
At the corners, they'll be screwed together with batten screws. The flat stakes will be fixed with 12G x 50mm screws.
Would 12mm reo be sufficient enough to pin the sleepers so they're reasonably solid?