Reference of the Pile Skin Friction with SPT

[Khurram Shehzad]

I came across a relationship in which Pile Unit Skin Friction is calculated with SPT values as follows;

f (unit skin friction) = 3 N(spt)

I could not find the reference of it, is any body know the reference.

 

[EireChch]

I dont have a reference for it. I see in Bowels that Meyerhof recommends 2 x N55 for driven piles in sand.

Regardless, I dont like calculating pile capacity by SPT. Use your SPT values to estimate a phi value in sand and gravel and nothing else.

Instead use the below for Sand and Clay

Sand

τs = Ks σ'v tan(δ);

where Ks = (1 + Ko) / 2 for Bored, CFA & Driven cast in situ piles. The value of Ks is increased by 40% for Driven precast piles
in-situ earth pressure coefficient Ko = (1-sinφ) OCR0.5

Clay

τs = αCu;

where α = 64.4Cu-0.96 (<0.85) for Bored, CFA & Driven cast in situ piles; and α = 0.5(σ'v / Cu)0.5 if Cu<σ'v or 0.5(σ'v / Cu)0.25 if Cu>σ'v for Driven precast piles

The above is form Flemming - Piling Engineering 3rd Edition

 

[fattdad]

Myerhoff's Terzaghi Lecture 1976.

f-d

ípapß gordo ainÆt no madre flaca!