Environmental Engineering Reference
In-Depth Information
Table 10.15 Linkage of Geotechnical Categories to Design Supervision Levels and Inspection Levels and
minimum requirements
Minimum recommended requirements for
checking of calculations, drawings, and
specifications
Geotechnical
Category
Design
Supervision Level
Inspection
Level
Characteristics
GC1
DSL1 relating
to RC1
IL1 relating
to RC1
Normal
supervision
and inspection
Self-checking: checking performed by
person who has prepared the design
GC2
DSL2 relating
to RC2
IL2 relating
to RC2
Normal
supervision
and inspection
Checking by different persons than
those originally responsible and in
accordance with the procedure of the
organization
GC3
DSL3 relating
to RC3
IL3 relating
to RC3
Extended
supervision
and inspection
Third-party checking: checking
performed by an organization different
from that which has prepared the
design
levels. This framework includes measures to ensure the quality of geotechnical investi-
gations, design calculations, the supervision of construction, and the monitoring and
maintenance of a structure after completion and is based on assumptions that all of
these aspects are carried out by persons with the appropriate expertise and experience.
The measures include many checklists of items to be considered, taken into account, or
receive attention in geotechnical design. There is also a requirement for good communi-
cation that involves the preparation of a Geotechnical Design Report and a Geotechnical
Investigation Report.
The reliability of geotechnical designs to Eurocode 7 may be verified by one or a combi-
nation of four methods: calculations, prescriptive measures, model and load tests, and the
observational method. When using calculations, design values are obtained using partial
factors and combination factors applied appropriately to characteristic actions and character-
istic material parameters or resistances. The characteristic values of parameters are selected
by the designer to account for the variability in the parameters and the extent of the failure
mechanism, while the partial factors and combination factors are chosen by national authori-
ties to take account of uncertainties in the calculation models and material uncertainties as
well as to provide appropriate levels of safety or degrees of reliability and robustness.
In designs to the Eurocodes, the combination of the partial factors, combination fac-
tors, and characteristic values aim to achieve designs with the appropriate target reliability
index. Recognizing that statistical information about the actions and material parameters
is often not available, particularly in geotechnical design, the values of the recommended
partial factors in Eurocode 7 have generally been chosen on the basis of a long experi-
ence of geotechnical design and building tradition. However, as the understanding of the
statistical nature of soil improves and as more research is carried out in this area, it is
anticipated that statistics and probabilistic analyses will be used more frequently to select
the characteristic parameter values, to calibrate the partial factors values and to assess the
reliability of geotechnical designs.
aCknoWleDgMentS
Helpful comments and contributions from Professor Jianye Ching, particularly on the vari-
ance reduction factors, and from Professor K.K. Phoon are gratefully acknowledged.
 
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