In most parts of the U.S. you don't
have to look far to find failed or failing
retaining walls. They can lead to
callbacks, unhappy customers, and
even worse, damage to property or
even serious injury.
Catastrophic failure (walls tipping
over completely) is unusual, partly
because the process often progresses
slowly and corrective action is usually
taken before the catastrophe can
occur. But that's not always true. One
rainy afternoon in about 1960, the
harmless-looking wall in Figure 1 suddenly
and spontaneously tipped over.
Fortunately my three sisters and I
were inside playing Monopoly instead
of out playing in the yard. The shock
of the impact of five tons of masonry
against our house, followed by twenty
tons of mud,