Performance of Anchors inside the Failure Wedge 2

[Obregon]

Hello. As you might know, some companies grout between the tendon and the soil in the failure wedge, and some government agencies require such grouting, the unbonded lentgth of the tendon being zero. Then, when these anchors are tested, some of the measured anchor capacity is from the soil within the failure wedge.

Since the tiebacks in service at any time are near the interim bottom of excavation and since they are drilled at a downward angle, most of the length (if not the entire length) are outside the active wedge.
In this case it is not only possible but advantageous to install the anchors without any free length. At worst, the tiebacks near the interim bottom of excavation only need a very short unbonded length.

However, I'm still intrigued with design issues and the fact that this practice has been succesful with others all over the years and within our own practice, when we've decided to go this way.

Any experiences to kindly share?

 

[r13]

Obregon,

Do you mind to provide a sketch to demonstrate your argument? I must have drank too much, after so many exchanges, I still couldn't figure out exactly what is the "weird method" that intrigues Mr. Schanabel and you.

BTW, I admit that I do not know Mr. Schanabel, nor read any of his work. So, please post his words may help my understanding. Thanks.

 

[PEinc]

Obregon, I have the highest respect for Harry Schnabel and the company he founded. Unfortunately, without substantiating facts, data, or examples, what Harry Schnabel wrote on this subject can or should only be considered as hearsay. Therefore, I would be inclined to ignore it until someone researches the issue and obtains solid evidence of satisfactory performance. Again, you can talk to Hank Schnabel, but it was Harry who originally wrote those comments in his 1st edition book. As with many things in life, you can push the envelope slightly and be OK. However, when pushing further, there may be a fine line between success and failure. Are you willing to experiment on a real job to find that fine line?

I understand that your the 10 meter free length may have been specified in order to cross the critical slip surface. Been there; done that. But, if so, what was the justification for reducing the free length to less than 10 meters? Did the slip circle location change? My comments about typically using a maximum 6 meter free length were applicable to anchored wall construction and not to a landslide situation. Sorry if I caused any confusion.

http://www.PeirceEngineering.com

 

[Obregon]

I thank you again PEinc

"Therefore, I would be inclined to ignore it until someone researches the issue and obtains solid evidence of satisfactory performance"

I believe this is the kind of rationale a wanted to hear, and you have made a point I could only have expected from a smart guy like you, without underestimating the comments and opinions of others.

Best regards.

Carlos R. Obregón

http://www.sueloanclado.com

 

[r13]

I apologize, If I misunderstood your concern.