Liquefaction Options - SPT

If you want to use the correction factors associated with a particular liquefaction calculation method, choose Pre-defined in the Methods tab of the Liquefaction Options dialog. The following Methods are available:

• Youd et al. (2001)
• Idriss and Boulanger (2008)
• Cetin et al. - Deterministic (2004)
• Cetin et al. - Probabilistic (2004)

If you choose to customize the correction factors, the following can be applied when performing a liquefaction analysis with SPT data:

Magnitude Scaling Factor (MSF)

The Magnitude Scaling Factor is used to adjust the CSR or CRR to an earthquake magnitude value of M=7.5.

The following options are available for MSF:

• None
• Tokimatsu and Seed (1987)
• Idriss (1999)
• Andrus Stokoe (1997)
• Idriss and Boulanger (2008)
• Idriss (NCEER)
• Idriss and Boulanger (2014)
• Youd and Noble (1997)
• Cetin et al. (2012)

Stress Reduction Factor (R_d)

R_d is the shear stress reduction coefficient, and is used to determine the maximum shear stress at different depths. Typically, values range from 1 at the ground surface to lower values at greater depths.

The following calculation methods are available for R_d:

• NCEER (1997)
• Idriss (1999)
• Kayen (1992)
• Cetin et al. (2004)
• Liao and Whitman (1986)
• Youd (2001)

Relative Density Estimation from SPT (D_r)

The relative density of a soil can be used to calculate the overburden correction factor, C_N. A number of methods are available for calculating the relative density from SPT values. The following options are available for D_r:

• Skempton (1986)
• Ishihara (1979)
• Tatsuoka et al. (1980)
• Idriss and Boulanger (2003)
• Ishihara Yasuda and Yokota (1981)

Fines Content Correction

The following options are available for fines correction:

• None
• Idriss and Boulanger (2008)
• Youd et al. (2001)
• Cetin et al. (2004)

K Sigma

Ksigma is an overburden correction factor used to adjust the CSR or CRR to a common effective overburden stress.

The following calculation methods are available for K_sigma:

• None
• Hynes and Olsen (1999) (NCEER)
• Idriss and Boulanger (2008)
• Cetin et al. (2004)

K Alpha

K_alpha is the static shear stress correction factor. It is used to adjust CRR values for the effects of static shear stresses. The most common applications of K_alpha is for steeper slopes and embankments.

The following calculation methods are available for K_alpha:

• None
• Idriss (2003)