One other caveat - don't expect the chain to be very sharp after this bit
of abuse. I needed to get another chain to restore the saw to it's proper
wood cutting use.

Having some experience with chainsaws-

Contacting the blade with dirt will ruin the blade (as stated above), but
don't do this with an expensive saw thinking that the blade can be changed
later. It'll also ruin the guide wheels and clutch too. In fact, it is
widely known among chainsaw operators that dirt = death to chainsaws. It
mixes with the oil and becomes a grinding compound.

Trench cutting has to be seen as an old saws dying gasp.

It is also extremely risky. If you unwittingly hit something solid, the saw
could bounce or kick back. It happens sometimes when you're cutting wood.
Its bound to happen when you are cutting into something when you don't know
what it consists of.

Having said all that, I cant decided if my advise would be- be careful, OR-
just don't do it.
--
Jack VK2CJC / MM0AXL
FISTS# 9666
Mid North Coast Amateur Radio Group
www.mncarg.org