Wall friction angle estimating Kp for soldier pile wall

[yakpol]

Hi,
I am estimating passive pressure Kp using coulomb formula for soldier pile wall. The value is very sensitive to the angle of wall friction. Say, for phi = 37 and delta = 16 degrees Kp = 7.7, for delta=0, Kp=4.0.
My concern is that passive earth pressure is assumed to act over the width of 3 pile diameters, so the idea of wall friction is somewhat muddled here. Any thoughts?

Thanks!

 

[PEinc]

I have often used numbers in the range that you have shown. I recommend that you use as little wall friction as you need to give you an economical soldier beam. You may not need to use the full 7.7. Are the soldier beams cantilevered or braced/tiedback? For cantilevered soldier beams, unless in hard rock, I usually call for at least as much toe embedment as the exposed height of the wall. For braced/tiedback soldier beams, I try to use at least 5' embedment in soil or in soil and rock, but 2' minimum if just embedded in rock. Put your passive resistance safety factor on the calculated, required length, not on Kp.

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