Civil Engineering Reference
In-Depth Information
ISO/CEN Standards for
identification & classification
Eurocodes:
EN 1990 Basis of Structural Design
EN 1991 Actions on Structures
Test Standards and Technical
Specs for ground properties
Geotechnical Design
(Eurocode 7: Parts 1 & 2) & NAs
European Standards for
the Execution of Special
Geotechnical Works
Other structural Eurocodes
e.g. EN 1998, EN 1993-5
Geotechnical Projects
Fig. 5.4
European geotechnical codes (after C&LG,
2007)
.
It is important to realise that by itself Eurocode 7 will not be the only European standard that will be
used on a geotechnical project. Other Eurocodes (most notably EN 1990, EN 1991 and EN 1998) will be
involved as will ISO testing and execution standards as shown in Fig.
5.4.
5.3 Using Eurocode 7: basis of geotechnical design
The clauses throughout Eurocode 7 are considered as either
Principles
(identified by the letter P imme-
diately preceding the clause) or
Application Rules
. Principles are unique statements or definitions that
must be adopted. Application Rules offer examples of how to ensure that the Principles are adhered to
and thus offer guidance to the designer in following the Principles.
Section 2 of EN 1997-1 describes the basis of geotechnical design and the code states that the limit
states should be verified by one of four means: by (1)
calculation
, (2)
prescriptive measures
, (3)
experi-
mental models and load tests
, or (4)
an observational method
. In this topic we shall concentrate solely on
geotechnical design by calculation (see Section
5.4)
although a prescriptive measure for the determination
of presumed allowable bearing values is touched upon in Chapter
9
.
To facilitate an appropriate design, projects are considered as falling into one of three
Geotechnical
Categories
, based on the complexity of the geotechnical design together with the associated risks.
Cat-
egory 1
is for small projects with negligible risk,
Category 2
is for conventional structures (e.g. foundations,
retaining walls, embankments) and
Category 3
is for structures not covered by Categories 1 and 2. It is
obvious that most routine geotechnical design work will fall into Geotechnical Category 2.
5.4 Geotechnical design by calculation
To enable the limit states to be checked, the
design
values of the geotechnical parameters, the ground
resistance and the actions (e.g. forces or loads), must be determined. Thereafter, a geotechnical analysis
is employed to show that the particular limit being checked will not be exceeded. A typical sequence of
the processes involved in the design calculations is shown in Fig.
5.5.
