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Re: Retaining Wall Design Methodology

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Stan, you seem to be apportioning only upward soil pressures on the wall
footing. If that is so, then why even have a heel feature?  Upward pressure
on the heel does not help with stability of the wall. 

The heel is useful for downward pressure the backfill imposes on it, which
helps stability against overturning. The heel experiences negative moment
for reinforcing purposes.

I assume you know all this perfectly well, which makes your question
puzzling for why the matter is of interest.

As an aside, I am aware of a California SE exam not far back where the exam
graders insisted, on appeal yet, that backfill pressures act only
horizontally on the wall, and cannot act vertically on the footing heel the
backfill is dumped down upon. On another Cal SE Exam, in 1981, the problem
writer/grader refused to believe there were three unique, equally valid sets
of solutions for forces on the two given lines of supporting piles,
depending on which two of the three applicable conditions of static
equilibrium one chose to solve the given dimensions and soil loading
conditions with to get horizontal and vertical reactions. He denied credit
to all examinees who hadn't read his mind correctly. Given the multiple
variations, like you present here, on how to solve most any problem, and the
habitual reluctance to admit any answer but the pre-ordained one, guessing
the state of mind of the examiners is actually the skill most needed to pass
this exam.

W. Gene Corley's remarks about the Calif SE exam in the Summer 2000 NCSEA
"Structure" magazine aren't just hypothetical; the lack of scrutiny and
quality control in this exam has long been appalling, and matched only by
the arrogance of its administrators. 

Charles O. Greenlaw SE    Sacramento CA

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