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H-Pile in rock

H-Pile in rock

H-Pile in rock

(OP)
When designing a temporary soldier piling/lagging system where rock is encountered below the excavation/dredge line, what are reasonable Kp values, assuming the h-piles are set in augered holes filled with lean concrete?  Any reference sources you can suggest? Thanks you.

RE: H-Pile in rock

Cosimo,

AASHTO Standard Specifications for Highway Bridges 17th Edition or LRFD 3rd Edition have guidance.

For permanent walls, AASHTO allows a total force per discrete vertical element of Fp, such that:

Fp = sD*(D+b^0.5)/[1+tan(B')]

where

s = unconfined compressive strength of rock mass
D = embedment depth of element in competent mass (AASHTO recommends discounting top 1 foot of embedment for permanent walls)
b = width of vertical element
B' = angle of dredge line measured from horizontal (sloping downward away from wall is considered positive angle in this case)

Determination of 's' can be tricky, as many AASHTO formula assume a RQD of 60%+. If the RQD is less than this amount, it is unclear what is the best course of action.

Hope this is helpful.

Jeff

Jeffrey T. Donville, PE
TTL Associates, Inc.
www.ttlassoc.com

RE: H-Pile in rock

Check out AASHTO's Standard Specifications for Highway Bridges.

Check out FHWA's Geotechnical Engineering Circular No. 4, FHWA-IF-99-015, Ground Anchors and Anchored Systems.

RE: H-Pile in rock

Say Phi = 45-50 deg. and you will get reasonable embedments

RE: H-Pile in rock

You will also get pretty reasonable embedment results if you treat the rock below subgrade as a very stiff clay.

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