Lateral Capacity of Drilled Concrete Piers

[skimboard20]

I am designing a foundation system for a single family residence that consists of drilled concrete piers and grade beams, per the recommendation of the geotechnical engineer. One wall in the basement retains about 8 ft of soil. I have designed a grade beam section for this wall that is about 6 ft wide and 2 ft deep, supported two drilled piers, one at the toe and one at the heel (approximately). My issue is resolving the lateral load induced by the retained soil. Of course, this is normally resisted soil friction, foundation key, etc. but with incompetent soil, I think I need to rely on the drilled piers to resist this load.

The geotech report suggests a lateral resistance of "maximum of 350 pcf(EFP)against the individual piers within the bedrock for 1.5 times the width of the piers". To be honest, I don't fully understand what this means. Any interpretation of this statement and its relevance in developing a lateral capacity of the drilled concrete piers would be greatly appreciated.

Other relevant info:
Piers are 16" diam. and reinforced.
Overall depth of piers is approx. 16 ft (10 ft min. into bedrock).

Thanks for the help!

 

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I think he means you can use passive pressure of 1.5*350pcf = 525psf/ft to design the pile as a pole footing to determine the minimum embedment. You still have to design the reinforcement for pile bending. 1.5 seems to be a factor considering arching