Analysis Methods - CPT
Triggering
A number of methods are available for liquefaction triggering. The most widely used approach consists of comparing the cyclic stresses with cyclic resistance of the soil (comparing CSR and CRR). Liquefaction is expected where induced stresses exceed the soil resistance.
The following methods are available for triggering of liquefaction:
- Robertson and Wride (1997)
- Modified Robertson and Wride (1998)
- Idriss and Boulanger (2004)
- Idriss and Boulanger (2014)
- Moss et al. (2006) Deteministic
- Moss et al. (2006) Probabilistic
Settlement
Liquefaction settlement calculated in Settle3 is caused by the reconsolidation of the liquefied soil. Reconsolidation strains are calculated, based on the maximum shear strains that developed during the cyclic loading. The following methods are available for determining the volumetric strain.
- Yoshimine et al. (2006)
Dry Sand Settlement
During dynamic shaking, it is well known that loose sands tend to compress and settle. During severe shaking this can cause liquefaction of saturated deposits. However, for dry sands liquefaction cannot occur since no water is present. For dry sands, dynamic shaking only causes the sand to compress and settle. The settlement addressing the seismic shaking is calculated in Settle3 using two different methods depending on the user input. If the user selects the Liquefaction method as Cone Penetration Test (CPT) then Settle3 will follow the CPT Dry Sand Settlement method which is similar to the SPT method except that it applies a correction factor to the standard penetration resistance (N1)60 based on the concept that soils with the same state parameter have the same response to loading (Robertson and Shao, 2009)
Lateral Displacement
The lateral displacement is calculated based on the maximum shear strain. The following formulations are available in Settle3.
- Zhang Robertson and Brachman (2004)
- Yoshimine et al. (2006)