Understanding Retaining Wall Design to Avoid Failure

08.27.15   Robert C. Rabeler, PE | More by this Author

Understanding Retaining Wall Design to Avoid Failure

This article is part of a series regarding lessons learned in geotechnical engineering.  These are real projects with real people, but the names have been omitted to protect those involved.

A two-tiered retaining wall was constructed using treated lumber timbers. The wall was constructed using timbers with short "T" sections behind the wall (similar to deadmen) to resist the lateral forces. Unfortunately, the wall was not designed by a geotechnical engineer and shortly after construction the wall failed, as shown below:

The "T" sections of the lower wall were fine; however, the reinforcing "T" sections for the upper wall were not extended beyond the edge of the zone of influence of the backfill (depicted by the red dashed line in the figure below). Had they been extended further into the backfill, the upper wall would have performed satisfactorily.

Lesson Learned: Retain a knowledgeable and experienced geotechnical engineer who understands soil mechanics when you are dealing with subsurface soil and groundwater conditions.

For more information, contact Bob Rabeler.

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