This retaining wall failed in 2010.  In order to BE a retaining wall, a wall must obviously NOT tip over and NOT slide. For a natural stone retaining wall, like the one shown here, the width at the bottom should be at least half of the height.  The thickness of the stone facing at the bottom of the wall was the SAME as the thickness of the stone at the top.  So, it was destined to fail.  The retaining wall contractor who installed this wall did not make the base wide enough.

So, if you have a 10-foot high retaining wall, the bottom row of natural stones should be at least FIVE FEET thick! That’s a lot of stone, or concrete, mortared together.  Also, the retaining wall contractor should backfill behind the wall with gravel and give that gravel a place to drain permanently using perforated pipes.

 

In this case, the “retaining wall” was nothing more than a thin layer of stone, stacked very steeply with topsoil fill behind it. This wall was destined to fail, and did, shortly after construction. We engineered a new retaining wall using the same stone, and placing layers of geogrid between the stones, going back several feet.

The unfortunate homeowner had to pay several thousand dollars to have the wall reconstructed.  If the retaining wall contractor had made changes in the beginning the failure may have been avoided.

You can see more of this project’s photos here.

(State PE Registration Map)

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