Utility Pole in Rock

[dik]

I've got a small project where a 70' utility pole is embedded 10% of the length in 'Shield' rock. I'm looking at using a program I wrote using the Bowling method with a high K value. I suspect anything that happens will occur within the first few feet due to the rock stiffness.

Any comments or suggestions why Bowling is inappropriate, or, is there a better approach?

Dik

 

[oldestguy]

Of course you have a log of the hole, right? How about all those geologic terms such as strike and dip?

 

[dik]

OG: not necessary the rock is extremely sound and not weathered. Granitelike. Better than dirt... and the practice is to set the poles in a cementitious grout. The 10% is apparently a Code thing in Ontario.

Dik

 

[Ron]

Dik...I would bet on fixity at even a lesser depth in competent rock. If grout is relatively high strength and the annular space is not large, most of the lateral strain will go directly to the rock so, yes, you are correct that everything will happen in the first few feet, probably even less.

 

[oldestguy]

This OG is stuck trying to see what Bowling is other than that round ball with finger holes in it. Regardless if one has a code requirement, it sometimes is difficult to get the inspectors to allow a different method, especially non PE engineers or journeymen. Getting technical, if there is the need to prove a change in methodology, I'd use a core boring, classify the rock, give percentage recovery for each core tun and use suitable geologic descriptive terms, run unconfined compression tests on intact cores.. Possibly some researcher has determined K values for different unconfined compression test values also. Any weak plane also needs evaluation.

 

[oldestguy]

I did find some help with this during a BING search. Darn scarce. Opinions yes, but proof ?

thread256-150798

Maybe Kp doesn't apply.

 

[dik]

Ron: The pole is cedar so not so stiff compared to rock... just looking for an embedment formula I can chuck in my design notes. Bowling is one that I have an SMath sheet for. With the cedar-rock interface, I doubt that Ka and Kp would come into play. I also have to determine the Code source for the 10% embedment, and, if there are any exclusions. Attached the 10pin paper for OG... a good paper IMHO.

Dik