Assessing and managing the risk of earthquake-induced liquefaction to civil infrastructure - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 119

framework, the value of undertaking costly analyses and tests can be com-
pared with the magnitude of the risk based on simpler assessment tech-
niques and thus justifi ed in specifi c instances.
The empirical assessment of the liquefaction potential, described in the
previous sections of this chapter, does not provide insight into the triggering
mechanism of liquefaction or the physics of the actual phenomenon.
However, numerical modelling of liquefaction does have the potential to
be used not only to improve our understanding of the liquefaction process
and but also to predict the liquefaction response. The distinct advantage of
such analyses is that the triggering of liquefaction, the post-liquefaction
stability and the resulting displacements can be estimated in a single time
domain analysis.
Several advanced elasto-plastic constitutive models have been devel-
oped, such as those based on nested yield surfaces (e.g. Prévost, 1977; Yang
& Elgamal, 2008), general plasticity (e.g. Pastor et al. , 1990; Ling & Yang,
2006) and bounding surface plasticity theories (e.g. Manzari & Dafalias,
1997; Li, 2002; Papadimitriou & Bouckovalas, 2002; Loukidis & Salgado,
2009). The use of such sophisticated numerical tools is based on fi rst cap-
turing the element behaviour from laboratory tests and calibrating the
model parameters, before considering the entire boundary value problem.
The calibration of advanced constitutive models is often demanding in
terms of the required laboratory data and time and therefore the use of
such models is still rather limited in engineering practice. Furthermore, the
accurate prediction of the liquefaction response in the fi eld when using
advanced numerical tools is of course highly dependent on the adopted
ground model, both in terms of geometry and the characteristics of the
strata but also the ground motion, each of which has its own uncertainties
and limitations.

5.3 Hazard quantifi cation

5.3.1 Permanent ground deformation
Modes of permanent ground deformation resulting from earthquake-
induced liquefaction, include:

• reduction in strength leading to reduced bearing capacity and hence
settlement;
• volumetric strain-related settlement;
• lateral spreading;
• fl ow failure; and
• tension cracks and pressure ridges.