NovoCPT covers the following methods for calculating Rd:

 

NCEER (1997) based on Seed & Idriss (1971)

rd= 1.0 - 0.00765 Z

rd= 1.174 - 0.0267 Z

rd= 0.744 - 0.008 Z

rd= 0.50

for z ≤ 9.15 m

for 9.15 m < z ≤ 23 m

for 23 m < z ≤ 30 m

for z > 30 m

Thomas F. Blake (FugroWest Inc., Ventura, California)

Idriss & Boulanger (2008)

(based on Golesorkhi 1997 and Idriss 1999 works)

Kayen et al. (1992)

rd = 1 - 0.012 Z