Shallow Pier Foundation Rotating Down On Hillside

[RFreund]

This is similar to the hillside power pole situation you typically see while driving. The pole is embedded into the hill side and is now X degrees from vertical as it rotates down the hill.

We have a situation where an existing residence built on a hillside has exiting balcony piers that appear to be sliding/rotating down hill (home appears to be ok). They would like to add on to the balcony but the proposed piers must be designed so as to not rotate down hill.

My questions:

Are there any references that discuss this topic?
How can you design for this situation? I thought about installing tie back helical piers but I'm not sure what the force on the pier would be.
Is this a slope stability issue?
Any other comments would be appreciated.

Thanks!

EIT

http://www.HowToEngineer.com

 

[RFreund]

Another hole pic.

EIT
www.HowToEngineer.com

 

[Riggly]

Is is possible that that whole wall slid away from the house? That is one mode of failure with retaining wall. Seeing that there is no soil at the toe of the wall, that makes is even more likely. Looking at the corner of the wall next to the house, there appears to be a gap with material falling out? Can you make further observation to confirm? If does not take much movement for that movement to affect your piles.

 

[dirtsqueezer]

Sorry- didn't see the wall below, only 1 pic w/ the other wall. Sounds like you've got someone working on it already that has real access to the site. Best of luck.