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Formulations for Poulos & Davis (1980) Method for Single Pile Settlement

Formulations for Poulos & Davis (1980) Method for Single Pile Settlement

Formulations for Poulos & Davis (1980) Method for Single Pile Settlement

Hey everyone,

Most of you know the Poulos & Davis (1980) for calculation of settlement of single pile. There are four or five charts. Have you ever seen formulation of these charts? I want to digitize that process, however, I do not want to deal with that extensive effort if there is something similar. Maybe you have created some excel charts?

RE: Formulations for Poulos & Davis (1980) Method for Single Pile Settlement

Interested to follow this.

The name is a long story -- just call me Lo.

RE: Formulations for Poulos & Davis (1980) Method for Single Pile Settlement

I digitized a curve from a book before by reading the x and y values from the curve and then created an excel table. I then plotted the values in excel and fitted a trendline to the plot to get the equation. Alternative way to obtain the points is to insert a scaled curve image into CAD and trace it with spline or points and export those points into excel by a lisp. For log scale you can manipulate the date in excel before plotting them so the trendline gives you higher R^2 value.

RE: Formulations for Poulos & Davis (1980) Method for Single Pile Settlement

I know we can digitize it, there are many softwares and web based apps to digitize easily. But the point is if there is anyone to share their formulas, excel files.

RE: Formulations for Poulos & Davis (1980) Method for Single Pile Settlement

I'll get you started
RH for L/d=50=-1.63(h/L)^4+11.2(h/L)^3-28.67(h/L)^2-32.64(h/L)-13.11
RH for L/d=25=1.56(h/L)^3-7.88(h/L)^2+13.25(h/L)-6.63
RH for L/d=10=1.62(h/L)^3-8.2(h/L)^2+13.9(h/L)-7.18

RE: Formulations for Poulos & Davis (1980) Method for Single Pile Settlement

I had to do a little research on input values before I could proceed. Poisson's ratio silt 0.3-0.5, sand 0.3-0.4, clay 0.1-0.3, sat. clay 0.4-0.5
and subgrade modulus from NAVFAC DM 7.1-219 Figure 6 is 11.36N-60.67 for clay and 5.70N+13.46 for sand in tons/ft^3. To convert to kPa multiply by 100.
E from Bowles Fdn Eng Table 5-6 sand E=500(N+15). Saturated sand E=250(N+15). Silt&clay=300(N+6) in kPa. To convert to ksf divide by 50.
So Rv=0.34v+0.83 as 500-2000 about same and for k=100 Rv=0.25v+0.88. Rk for L/d=50
Rk=-0.45ln(k)+4.78, for L/d=25 Rk=-0.30ln(k)+3.5, for L/d=10 Rk=-0.17ln(k)+2.4.
Since I was interested in an end bearing helical pile with a slender shaft 25d long in 50 blow silt
Ρ=50Kx0.12/(336K/SFx0.36 ft)=0.05 ftx12”/’=0.6 inches which is less than half expected. Let us know if you have better luck.

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