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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 (Rd)

Rd 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 Rd:

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

Relative Density Estimation from SPT (Dr)

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

  • 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 Ksigma:

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

K Alpha

Kalpha 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 Kalpha is for steeper slopes and embankments.

The following calculation methods are available for Kalpha:

  • None
  • Idriss (2003)
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