Assessing and managing the risk of earthquake-induced liquefaction to civil infrastructure - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 112

operators of civil infrastructure to understand liquefaction in the context
of the risk it presents, and therefore make appropriate decisions in terms
of risk treatment requirements. Liquefaction risk is the product of the likeli-
hood of liquefaction-related hazards (of a certain magnitude), and the
consequence in terms of the effect that liquefaction hazards will have on
the system performance. Put simply, liquefaction hazard alone does not
necessarily present a problem to infrastructure owners and operators;
however, where the consequence of the liquefaction is unacceptable to the
overall performance, risk mitigation measures may be required.
The framework presented in this chapter could be used for any natural
or man-made hazards that are likely to impact on infrastructure projects.
The focus of the paper is on civil infrastructure systems, which could include:

• transportation networks (road, rail, airports and seaports);

• water and wastewater networks; and

• energy generation and distribution networks.

Figure 5.1 illustrates the effects of liquefaction on infrastructure.
There are particular features of such infrastructure systems that merit
special consideration in a risk framework, such as their signifi cant linear
extent, which means they pass through many different geological settings
and are therefore vulnerable to many geohazards. For individual buildings
on the other hand, the risk presented by liquefaction potential is reasonably
well constrained and, provided that the overall performance requirements
of the building are clearly defi ned, liquefaction risks can be managed
through appropriate foundation design. The challenges for infrastructure
systems, due to their wide geographical distribution, are greater, and the
required performance is often more complex.
The stages of the risk management framework presented in this chapter
follow the standard steps (Free et al. , 2006) of:

• risk assessment (hazard identifi cation, risk estimation, risk evaluation);
• risk treatment;
• risk acceptance; and
• risk communication.

The risk terminology used in this chapter follows the defi nitions provided
in ISO Guide 73. The focus of this chapter is on the risk assessment stage
of the framework, with the subsequent stages being dependent on the spe-
cifi c requirements of the owners/operators.

5.1.1 A framework for liquefaction risk assessment

As described above, the assessment of liquefaction risk is the focus of this
chapter, in terms of likelihood and its impact. The framework presented in