Managing risk and achieving reliable geotechnical designs using Eurocode 7 - Risk and Reliability in Geotechnical Engineering - page 393

is the requirement in §2.8(1)P that all the assumptions, data, calculation methods,
derivation of characteristic values, and the results of the ultimate and serviceability
limit state verifications shall be recorded in a Geotechnical Design Report (GDR),
which is required for all geotechnical designs, however, large or small. Furthermore,
it is required in §3.4.1(1)P that the results of a geotechnical investigation shall be
compiled in a Geotechnical Investigation Report (GIR), which shall form part of
the Geotechnical Design Report. Another quality management requirement, which is
given in §2.8(6), is that an extract from the Geotechnical Design Report containing
the supervision, monitoring, and maintenance requirements for the completed struc-
ture shall be provided to the owner/client. Some comments on the requirements for
inspection and monitoring are given in (g) below.
d. Measures aimed to reduce errors in design and execution, including gross human
errors : Unfortunately, as many case histories and researchers have shown, for exam-
ple, Sowers (1993), human error is a factor in many geotechnical and structural fail-
ures. Simpson (2011) in investigating geotechnical failures, identified the following
types of errors in geotechnical design which, in his experience, were depressingly
common: arithmetic errors, lack of expected basic knowledge, failures of communi-
cation, and oversight or misunderstanding of important information, for example,
from geotechnical investigations. Hence, systems need to be included in the design
process to reduce the occurrence of such errors and, if they occur, to identify and
remedy them. The checklists and Geotechnical Design Report referred to in the previ-
ous paragraph are examples of practical measures in Eurocode 7 to reduce errors in
geotechnical designs.
e. Adequate robustness : Robustness is the ability of a system to resist damage while
maintaining its important functions. Robustness is not limited to physical structures
but robustness principles can also be applied to management systems to reduce the
effects of unknown risks (Calgaro, 2011). Geotechnical design calculations gener-
ally involve the consideration of a relatively small number of variables to describe a
complex design situation, which, in addition to the known variability of the ground
properties and actions, can also involve unforeseen variations in the actions and
the geometry. Designs need to account for unforeseen variations in the actions and
geometry that could occur due, for example, to the disposition of the ground strata
not being precisely described or due to construction activity affecting the actions or
geometry. Designs to Eurocode 7 accommodate such unforeseen secondary effects,
including minor human errors, by including appropriate safety margins on the partial
factors and design measures and management systems to ensure that designs are suf-
ficiently robust.

f. Efficient execution : Construction work should be carried out in accordance with rel-
evant execution standards in the case of geotechnical design situations for which such
standards exist, for example, CEN has published the following execution standards,
all with the prefix “Execution of Special Geotechnical Works” to their titles:
• EN 12699

Displacement piles

• EN 12715 Grouting

• EN 12716 Jet grouting

• EN 14199 Micropiles

• EN 14475 Reinforced fill

• EN 14490 Soil nailing

• EN 14679 Deep mixing

• EN 14731 Ground treatment by deep vibration

• EN 15237 Vertical drainage