NovoCPT evaluates the factor of safety against soil liquefaction based on the following methods:

 

Robertson 2010

NovoCPT uses the following equation for calculating factor of safety at each depth:

 

FS = (CRR7.5 / CSR) * MSF * Kα

 

where CRR7.5 is the Cyclic Resistance Ratio for earthquake magnitude of 7.5, calculated from the flowchart proposed by Robertson 2009, also shown on Figure 1 below,

CSR is Cyclic Stress Ratio (read this article), MSF is Magnitude Scaling Factor (also known as Km), Kα is the slope effect, assumed to be 1.0

 

Figure 1 : Flow chart to evaluate cyclic resistance ratio (CRR7.5) from CPT, after Robertson 2010.

 

Idriss and Boulanger 2006

For details of soil liquefaction analysis please refer to "Soil Liquefaction During Earthquake" by I.M. Idriss, R.W. Boulanger. It should be noted that in this method, user can enter sieve test results (fines content %) if such data is available. Fines content will then be used for fines content correction carried out for soil liquefaction based on Idriss and Boulanger method.