At 04:06 PM 1/20/2005, you wrote:
G'day,
| BTW 10% plus two feet is the recommendation of the
| Lineman's and Cableman's Handbook, 7th edition, by Edwin
| B. Kurtz and Thomas M. Shoemaker, page 11-3, both in the
| text and in Table 11-1.
|
| Of course it is soil dependent and in rock the depth is significantly
| less.
Not sure I like that last bit. What exactly does "significantly less"
mean? I've planted a few 28 foot poles and wouldn't consider anything
less than 4.5 feet depth particularly if I'm going to be swinging about on
it. Sods law says when she tips you'll be under it when it hits the
ground. I guess if it's in a 3 foot hole pecked into rock it will only
tip as far as the soft packing allows. Experience during my time with the
Post Office, now BT, in the UK suggests that concreting a pole in
seriously reduces its working life.
Regards,
Mike VP8NO
OK, Mike --
I was just trying to provide the reference to those who needed the info.
And I didn't think that anyone would be going into rock. But I will
reproduce the table for everyone's benefit.
First off, the text reads "A rule for determining the setting depth in soil
is to take 10% of the height of the pole and add 2 ft, with a minimum of
5 ft. And this is for poles in a straight line. If the pole is an angle
point or a corner point it should be set AT LEAST 1/2 ft deeper."
Obviously the depth is a function of load and of soil conditions so
these guidelines are just that, guidelines. If the soil is unusual
then you need to set the pole deeper and at some point you will need
a soils engineer to sort out the details.
So here is the table for both average soil and rock. It is not MY table
but rather the table in the Handbook for Linemen, based on decades
of experience. The guidelines for typical poles match the formula for
soil, but the very shortest poles and the tallest poles have obviously had
a fudge factor added.
Pole length Setting Depth Setting Depth
in feet in Soil in Rock
20 4.5 3.0
25 5.0 3.5
30 5.5 3.5
35 6.0 4.0
40 6.0 4.0
45 6.5 4.5
50 7.0 4.5
55 7.5 5.0
60 8.0 5.0
65 8.5 6.0
70 9.0 6.0
75 9.5 6.0
80 10.0 6.5
85 10.5 7.0
90 11.0 7.5
95 11.0 7.5
100 11.0 7.5
105 12.0 8.0
110 12.0 8.0
115 12.0 8.0
120 13.0 8.5
125 13.0 8.5
130 13.0 8.5
135 14.0 9.0
73 -- John W0UN
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