geotech (version 1.0)

SPT: Standard Penetration Test (SPT) Corrected N-values

Description

These functions are used to calculate corrected blow counts (N-values) for the Standard Penetration Test (SPT). Function N60 calculates corrections for field procedures, and function N160 calculates corrections for field procedures and overburden pressure.

Usage

N60(N, Lr, Db, SS = TRUE, E = 0.60, metric)
N160(N60, sigma, metric)

Arguments

N

raw SPT N-value

Lr

rod length (ft or m)

E

hammer efficiency as a decimal (default: 0.60)

Db

borehole diameter (in or mm)

SS

logical variable: TRUE for standard sampler [default]; FALSE for sampler without liner

N60

SPT N-value corrected for field procedures

sigma

effective vertical stress at the depth of interest (psf or kPa)

metric

logical variable: TRUE (for metric units) or FALSE (for English units)

Value

• N60 = SPT blow count (N-value) corrected for field procedures, after Skempton (1986)
• N1,60 = SPT blow count (N-value) corrected for field procedures and overburden pressure, using the Liao and Whitman (1986) stress correction

References

Liao, S.S.C., and Whitman, R.V. (1986). "Overburden Correction Factors for SPT in Sand", Journal of Geotechnical Engineering, Vol. 112, No. 3, pp. 373-377, ASCE. Skempton, A.W. (1986). "Standard Penetration Test Procedures and the Effects in Sands of Overburden Pressure, Relative Density, Particle Size, Aging, and Overconsolidation", Geotechnique, Vol. 36, No. 3, pp. 425-447.

Examples

##  Example code for SPT blow count (N-value) corrected for field
##  procedures
N60(N = 11, Lr = 25, Db = 4, E = 0.50, SS = TRUE, metric = FALSE)

##  Example code for SPT blow count (N-value) corrected for field
##  procedures and overburden pressure
##  In English units
N160(N60 = 8, sigma = 1500, metric = FALSE)
##  In SI units
N160(N60 = 8, sigma = 90, metric = TRUE)