Managing risk and achieving reliable geotechnical designs using Eurocode 7 - Risk and Reliability in Geotechnical Engineering - page 391

§12.7(2) several examples where monitoring should be applied in the case of embankments;
these include
• Where the stability of an embankment acting as a dam to a large degree depends on
the pore-water pressure distribution in and beneath the embankment
• Where surface erosion is a considerable risk
10.2.3 risks due to adverse water pressures
Water pressures are identified in Eurocode 7 as a particular hazard that can pose significant
risks in geotechnical designs and can be difficult to treat in order to achieve a consistent
level of safety. As shown in Section 10.4.3, Eurocode 7 provides separate partial factors for
designs against situations involving failure due to static water pressure causing uplift and
hydraulic heave due to water seepage pressures. The need to consider the risks due to water
pressure in the case of retaining structures is mentioned in §9.6(2)P of Eurocode 7, which
refers to the example given in §9.4.1(5) of a critical limit state occurring in the form of dam-
age to nearby structures or services due to wall movement, even though collapse of the wall
may not be imminent. The treatment of water pressure in geotechnical designs, including
how the characteristic value should be selected and whether or not they should be factored,
is an aspect that is under discussion. The revised version of Eurocode 7, due to be published
in 2020, is likely to provide more guidance on this.
10.2.4 geotechnical investigations and geotechnical risks
Since soil is a natural material, not manufactured under controlled conditions like concrete
and steel, its properties are not specified, as in structural design, but need to be determined.
Hence, Eurocode 7 has two parts: Part 1 providing the general rules for geotechnical design
and Part 2 providing the requirements for carrying out ground investigations and deter-
mining the value of soil parameter values. A geotechnical investigation with field and/or
laboratory tests to establish the stratigraphy and determine the soil parameter values is the
first part of the geotechnical design process. According to §2.1.1(1)P of Part 2 of Eurocode
7, geotechnical investigations shall be planned to obtain the relevant geotechnical informa-
tion and data required to manage the identified and anticipated project risks. The quality
and extent of the geotechnical investigations should therefore be sufficient to reduce the risk
of unforeseen unfavorable ground conditions that could cause a geotechnical failure, unex-
pected costs, or delays to a project.
10.3 relIabIlItY requIreMentS In DeSIgnS to euroCoDe 7
10.3.1 basic requirement
The basic requirement for a structure designed to the Eurocodes, including a geotechnical
structure designed to Eurocode 7, as stated in §2.1(1)P of the head Eurocode, EN 1990:
Basis of Structural Design (CEN, 2002) is that it shall be designed and executed in such a
way that it will, during its intended life, with appropriate degrees of reliability and in an
economical way:
• Sustain all actions and influences likely to occur during execution and use, and
• Remain it for the use for which it is required