Vs calculation parameters

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LiqIT provides the following methods for assessing liquefaction potential based on Vs measurements:

1. Eurocode 8 (1997)

2. NCEER (1997)

3. Andrus et al. (2004)

4. Juang et al. probabilistic (2001)

NCEER method

When the NCEER proposed method is selected, Cyclic Resistance Ratio is calculated using the normalized VS value (VS1) and a boundary shear wave velocity value (VSC1) that depends on the fines content of the soil. The boundary values are:

•	Vs1c = 220 m/s for sands and gravels with fines contents less then 5%

•	Vs1c = 210 m/s for sands and gravels with fines contents of about 20%

•	Vs1c = 200 m/s for sand and gravels with fines contents greater than 35%

You may provide a constant value for Vs1c or allow the program to automatically adjust Vs1c value based on the fines contents entered.

Note

The NCEER method is only applicable to uncemented Holocene-age soils.

Andrus et al. (2004) method

When the Andrus et al. method (2004) is selected, an age correction factor (Ka1) for high Vs1 values caused by aging (Vs1 is the stress normalized value of Vs) is applied. Typical values of Ka1 are displayed below:

Time (years)	Age correction factor
1	1.09
10	1.01
100	0.94
1000	0.88
10000	0.83
100000	0.78

You must provide the age of the soil in years for LiqIT to calculate Ka1.