Phi Angle Weathered Rock (Piedmont)

[nhb11]

I am searching for any referance material
for estimating shear strength parameters
for piedmont residual soils (silt/micaceous silts/weathered rock)??

Anyone know of good ref. material sources?

 

[nbr1]

Maybe cohesion would be more appropriate.
I'm at a loss as how to define shear strength parameters
from weathered Piedmont (Eastern US)sampled generall as sand (50 - 100+) blows per foot.

 

[PSlem]

http://www.cpt-robertson.com/pdfs/piedmontsitecharacterization.pdf

 

[msucog]

here's numbers off top of my head
25-38+ degrees
silts 26-35
micaceous silts 24-33
PWR 36-38+

but keep in mind the erratic nature (both horizontally and vertically) of the piedmont. run multiple tests on the specific soils to confirm.

 

[BigH]

Might want to check out Dr. Mayne's site - he has written some papers on the Piedmont.

 

[msucog]

dr. mayne is certainly one of the most well-respected professors in the piedmont area. my numbers based on my personal experiences. by the way cohesion is usually pretty low.

 

[nbr1]

FHWA Manual IF-99-025 (Drilled Shafts: Construction Procedures and Design Methods)suggests PWR would be
treated as an Intermediate Geomaterial (IGM).

My take on this is that PWR should be treated as a
cohesionless IGM; since my experience indicates little fines in PWR.

That being the case; the manual presents
a method for calculating phi' - but does not give an upper bound for such materials other than to say not to use
N>100bpf in the equation.

This give phi' as high as 57 degrees in some instances. I have a site where PWR is signicant to depth and am interested in determining skin friction values; which will depend on selection of phi'. Anyone have upper bound idea of phi' in PWR?????

38+ leaves a lot on the table........