Whether you are looking for a lower cost retaining wall to enhance your yard or to support your driveway, the Interlocking Concrete Block (ICB) (a.k.a. segmental concrete block) retaining wall may be your best option. Up to 4 feet tall (base to top of wall), it can be designed and installed by a qualified landscaper. Over 4 feet tall, it needs to be designed with geosynthetics by an Engineer. Regardless, it is typically less costly to install than a cast-in-place concrete wall because it does not need to extend to frost depth and the total amount of concrete is less.
The ICB wall is not mortared. One block rests on top of the next and on top of a compacted gravel leveling pad. The blocks are typically filled with crushed stone. So, when the soil below it moves due to frost, the wall moves with it, and back again when the frost is out of the ground.
The purpose of the geosynthetic is to engage friction with soil behind the wall. This friction, the friction at the base of the wall block, and the soil within the embedment depth at the toe of the base block work to resist the soil pressure tending to push the wall over. The design needs to take into consideration the height of the wall, natural soil and water conditions, the materials to construct the wall, and other factors. The drainage and compaction of soil at the base and behind the wall are key to its stability.