Managing risk and achieving reliable geotechnical designs using Eurocode 7 - Risk and Reliability in Geotechnical Engineering - page 388

The complexity of a geotechnical design is affected by the following geotechnical factors
identified in Eurocode 7, which, when they are abnormal and severe, constitute hazards that
need to be taken into account in geotechnical designs:
• Ground conditions
• Groundwater situation
• Regional seismicity
• Inluence of the environment
The complexity of a geotechnical design is also affected by the vulnerability of the pro-
posed structure to its surroundings and the vulnerability of neighboring structures and
services to the impact of the proposed structure. The vulnerability of the structure is a
function of the nature and size of the structure itself, and its elements. Geotechnical risk
is a function of two factors: the geotechnical hazards listed above, plus the vulnerability
of the structure and neighboring structures, and services to the impact of the proposed
structure.
10.2.2 levels of risk and geotechnical Categories
Eurocode 7 identifies different levels of risk in geotechnical designs, referring to design situ-
ations involving negligible risk, no exceptional risk, and abnormal or high risk, which are
associated with the three Geotechnical Categories, GC1, GC2, and GC3, as shown in Table
10.1, adapted from Orr and Farrell (1999). GC1 corresponds to structures with low haz-
ard and vulnerability levels and hence negligible risk, GC2 corresponds to structures with
moderate hazard and vulnerability levels and no exceptional risk, and GC3 corresponds
to structures with high hazard and vulnerability levels and hence abnormal or high risk.
Eurocode 7 provides the following examples of typical structures with these different levels
of geotechnical risk:
• Examples of structures with a low level of risk, that is GC1, are small and relatively
simple structures and agricultural buildings on ground that is known, from compa-
rable local experience, to be sufficiently straightforward and does not involve soft,
loose or collapsible soil, or loose fill;
• Examples of structures with no exceptional risk, that is GC2, are conventional types of
spread, pile, and raft foundations on ground that is not difficult and where the ground
conditions and properties can be determined from routine investigations and tests;
• Examples of structures with abnormal or high risk, that is GC3, are very large/unusual
structures on ground where the conditions are unusual or exceptionally difficult.
The use of the three Geotechnical Categories is not a Principle but is presented in Eurocode
7 as an Application Rule and hence is optional. The advantage of the Geotechnical Categories
is that they provide a framework for
• Assessing the level of risk in a geotechnical design
• Selecting the appropriate geotechnical investigation and testing methods and design
procedures
• Identifying the appropriate personnel to carry out the design
As noted in Section 10.2.1, the complexity of a geotechnical design situation and
the associated risks affect the minimum requirements in designs to Eurocode 7 for the