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Re: Retaining wall rotation

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The rule of thumb I learned in school, for loose granular soils, the wall needs to move approximately 1" in 20' to develop active pressure.  To develop passive pressure, movement of 1" in 2' is required (factor of about 10).  For a denser granular soil, the values may be between 1/2 and 1/3 of the previous movements.  For your case of 12' height, for a dense soil, this would indicate a movement of approximately 3/16" to 1/4" (versus 5/8" for loose soil). Hope this helps.

Eric Ober
Cagley & Associates
Rockville, MD

"John P. Riley" wrote:

A homeowner made an insurance claim on his retaining walls, one each side of the front of his underground home.  Both walls have rotated since their construction in 1979, one has an outward lean of about 1/8" in 8" (just had my little torpedo level with me . . . not real accurate) and the other is about 1/4" in 8"; both are 12' high tapering to 0' in 12' (i.e.: they are 45 deg triangles). I am about to prepare a report, saying among other things that retaining wall movement is inherent.  But I forget "how much" movement is to be expected.  Of course, I know its impossible to say for all cases, but I'm looking for an 'order of magnitude' number as a percent of height.__________________
John P. Riley, PE, SE
Riley Engineering
20 Oakwood Drive, Blue Grass, Iowa 52726
Tel & Fax:  319-381-3949