"The Natural Philosopher" wrote:
Al Reynolds wrote:
Outside my back door is an earth bank, sloping
backwards at about 10 degrees to the vertical.
There is an un-reinforced concrete footing which
is 1.5ft high and about the same deep, followed
by 3.5ft of dry stone walling, maybe 8" deep. The
remaining 6ft of bank is not retained by any structure.

In total, I am guessing that this is considerably less
support than a 330mm blockwork wall, and it has
all been in place for about 80 years.

For a start thats only 5 ft, not ten foot high as a structure, and
secondly, I bet the remaining 6 ft slopes well back from the lip.

Jut for info, the structure may only be five foot high, but the
bank is eleven foot high. The whole thing slopes at about ten
degrees to the vertical. Above the dry-stone wall it slopes at
about 45 degrees for about a foot, then carries on up at ten
degrees from the vertical for the next five foot.

All this is incidental, of course. The reason for my earth bank
being retained the way it is is because of the local soil type,
which is structurally quite stable unless exposed to severe
weathering. My point was that unless you investigate the local
conditions then any assertions along the lines of "this will work"
or "that won't work" are unlikely to be completely accurate.

To make the point that any structure can go if enough unusual conditions
are imposed on it. Boscastle has been there a couple of hundred years, not
a mere 80....:-)

Very good point. Must have a look at that earth bank some time...

Al