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Permanent Anchors

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Sercant

Sercant

Geotechnical
Joined
May 2, 2016
Messages
6
Location
TR
Hello Guys,

I am working on a project and implementing lots of permenant anchors to avoid any potential landslide. Actually material where the anchor bonds were implemented is not that very bad but, a landslide governed previously on that surface.

In any case, we implemented lots of anchors with load cells and we are following the behaviour of anchors by time. We tested the all anchors up to proof loads and locked according to design loads. Anyhow, in some anchors, load started to be increased and in some of them is started to lose. Actually i can understand that anchor can lose the load due to movement of anchor head and etc. But increasing load can note that some movement is going on the slope.

For now %90 of anchors are following the normal case. But i need to find some documents to if this situation can be acceptable.




 
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To be honest, I would expect all anchor loads to be increase.

For example, if you perform this analyses in Plaxis, you can see that anchor forces increase after excavation (or after movement of slope, in your case.)

Imagine. Slope wants to move down, anchors try to hold them. The more slope moves, the more anchor force will be exerted. Actually, this is the main idea behind bolts. We do not prestress them (or a little amount) and their stresses increase with movement.

So, what you should do is to investigate why there anchors with decreasing forces? Are there any unexpected backward movements? Or simply,these anchors lose the bound between grout and soil.

Last thing (irrelavant): It is good that you use load cells in permanent anchors. But I never trust to permanent anchors. They are very fragile. And load cells have certain lifespan. So, what will you do if these loadcells are broken or not working anymore? Be careful. Permanent anchors -even though we carefully implement them in the site- may rust and lose the strength. I always try to solve without anchors, if my retaining system will permanently.
 
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bdbd, the reason of losing load at anchors are totaly relevant with displacement of the anchor head. We observed and measured some settlements under anchor head,since the ground profile is so soft. For that reason anchors seems to be losing capacity.
 
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