All gravel used under or behind a retaining wall needs to be compacted to prevent future settling, and to strengthen the wall by locking the block and gravel together.
Contrary to popular belief, the retaining wall blocks themselves are not what retains the soil. Even though the blocks weight 70lbs each, they are too light to hold back the soil.
To properly compact a retaining wall, the compactor is run a minimum of 2 passes on top of the blocks and is extended all the way towards the back of the cut.
Compacting directly on top of the blocks is recommended by Allan Block as it increases the strength by about 30%.
This step is skipped by most contractors. It Is pretty nerve racking to compact a wall (it feels like the wall is going to collapse!), and takes extra time to build the wall because you need to place each row of block, backfill it with gravel, clean the retaining wall block off, and then compact it.
Regardless of how much work is required we do our very best to build every Allan Block retaining wall as strong, level, and straight as we can. All of our walls are submitted to Allan Block for quality control, giving everyone piece of mind that your project is going to last