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On Thursday, 13 December 2018 21:18:59 UTC, Andrew wrote:
On 11/12/2018 22:20, Tim Streater wrote:
In article , Andrew
wrote:

If the hole is 0.06 metres deep, I was assuming that the 'posts'
actually had a square metal plate on the bottom which would keep
the post upright, so all it needs is a cap of concrete for the
situation when some drunken russian labourer reverses into one.

If it's 6cm deep, the post is going to go over if someone pushes it
with their little finger.


0.6 * 0.6 * 0.06 = 0.0216 cu m, which is 50 Kilograms.

You'd need a very strong little finger to push that over
(not forgetting the adhesion of the concrete to the ground).

adhesion to soil is near zero. The problem with concrete
is lack of tensile strength, so it fails easily if deficient in
thickness. 6cm is not generous.

But will survive pushing with a little finger fine.