Guy Anchors

There's several types of guy anchors.  Here's some comparisons and what I have done.  But first a brief review of how they work.

The effectiveness of an anchor is determined by the weight of the cone of dirt the anchor would remove if pulled out.  The angle (base radius) of the cone is determined by the soil.  Surprisingly, sand is better than one might expect because as pressure is applied to the sand it tends to disperse the force in a wider pattern.  OK, the idea is simple, the math is easy, but you probably have to check tables or ask a soils engineer to find out the angle and weight appropriate for your soil.

Coil type screw anchors:  Avoid them.  Since the length of the anchor is essentially a spring, vibration is constantly working the soil loose.

Posts:  I can't get excited about that.  The applied pressure is trying to pull the post over.  It's nice to have the guys up where people won't run into them, but you can usually locate the anchors where they are out of the way.  This method could be satisfactory if a substantial amount of underground work were done to provide vertical support for the post and then "short guy" the post to a very heavy anchor.

Trees:  A forester will tell you that trees are very strong at the base and often they can be drilled into or through without hurting them.  In my case I don't have any trees in the right location and the resident local arborist would frown heavily anyhow. 

Screw anchors with the slotted disc end:  They are good.  Power and telephone companies have used them for years and they can bend a 60 foot power pole over with them.  However, we've also seen a lot of cases where a power down guy is just hanging limp.  Those are cases where the disc on the end simply was not into a firm base.  Also, in rocky soil they can be a real pain to install.

Ed's anchors:  Yes, it's a lot more work and more expensive.  I agree, it's overkill, but I've always looked at it as it's me up that tower and I want the tower to stay there.  I want the confidence factor.  Aside from being very sufficient for the job, this style of anchor has the advantage that the concrete base is well below the surface and the rod can be cut off easily leaving nothing afterwards that would be in anyone's way. 

After carefully measuring out the guy locations I drive a post in the ground for a marker.  Then I dig a hole four feet long, eighteen inches wide and four feet deep two feet behind the marker post and perpendicular to a line to the tower.  All of these dimensions can (and will) end up bigger because it is difficult to dig such a hole.  I use one inch, or larger, solid steel rod with a chunk of pipe welded on as a T on one end and the appropriate connecting head welded on the other end.  The rod is available in 21 foot lengths which makes three seven foot sections.  The supplier will usually cut them for you for a "cutoff" fee so you can transport them easily.  The rod is cleaned up and painted with zinc paint and the exposed end is then covered with ordinary silver spray paint.  The rod goes into the hole in a channel dug at the right height and angle to face the tower and the hole is filled with concrete two feet from the surface.  Then I fill the hole and mound the remaining dirt back over the area, or remove the excess dirt.  Here's some pictures.

A shovel is needed.

 

This shovel works much better.  This is a rental; about $200 per day.

They aren't neat holes, they don't have to be.  I said it would end up bigger than 4 x 4 feet, but

more is better and cement is $3/cubic foot

Here's the hole filled with concrete two feet from the surface.  One and one-third yard of

concrete went into each hole for a weight of 5400 pounds.  The extra one third yard of concrete

was my "make sure there's enough" factor.

OK, this isn't the same hole, but you can see the end result.

EST 31/07/2007