This seems like a straightforward question, right? But you would not believe how many walls we get called on that are having problems. Many of these problems are directly related to lack of compaction. When starting your wall, the first thing you do is dig out a trench to build your leveling base. If you dig the trench, and level all the loose material at the bottom without compacting the base of the trench, chances are your wall will see some amount of settlement. Next, you pour the base rock into the trench to form your base. If you do not compact the base rock to make it nice, consolidated, and tight, your wall will most likely see some settlement. Compacting the bottom of the trench and the base material is a key factor in building a quality wall that will not settle.
Now that you have a well compacted base that is level, you start the wall by placing the first course of Allan Block. Fill the cores of the block and behind the block with wall rock, a compactable aggregate. Then, place your 8 inches (2.5 cm) of infill material to be basically level with the top of the block. If you continue to build the wall like this, course by course without compacting the wall rock and infill material, it creates another possibility of settlement.
Notice a theme?
Without compaction your wall will settle. There is no question about it.
Settlement can cause lots of complications, some esthetic and some structural. Esthetic issues are an uneven and out-of-level block course, or even courses of wall that roll forward or backwards, among other things. Structural issues from settlement behind the wall will put additional “down drag” force on the geogrid layers and could cause significant damage to its life span.
So, if you have not figured out the answer yet…YES…COMPACTION IS NEEDED WHEN BUILDING ANY SEGMENTAL RETAINING WALL. See our Installation Guides for proper construction methods.