In 2007, a retaining wall at the Lowe’s Home Improvement store in Prescott, Arizona began to fail.  This was a very tall retaining wall, and was very expensive to litigate and repair.

There are many opinions about the root cause of the failure.  We offer no opinions about the failure.  Although we have been retained on numerous projects to provide expert witness services for retaining wall failures, we were not involved in this  project.  We neither designed, constructed, nor assessed the wall after failure.

What the photos (below) show is simply fascinating.  You can see that the “soil-and-geogrid” combination is incredibly stable!  These walls are called Mechanically Stabilized Earth (MSE) walls, or Segmental Retaining Walls (SRW) or even geogrid walls.  What is important to remember is that the “WALL” is the “geogrid-and-soil” combination.  The layers of geogrid and the soil between the layers form a large cube of soil that won’t slide and won’t tip over.  The blocks at the face can be thought of as “erosion control”.

Those blocks are not doing any of the hard work in holding back the hillside!  A 75 to 100 pound block can’t hold back a thousand tons of soil!  These photos clearly show that the geogrid-reinforced soil mass is standing vertically.  As a whole, it is stable.  But, of course, the exposed area will get washed away and will fail.

This unfortunate project had no winners.  Again, the purpose of these photos (and this post) is to show the power of geogrid reinforced soils, not to blame any person or product for the wall failure.

(State PE Registration Map)

 

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