When designing a geotechnical structure, the engineer needs to identify the possible ultimate and serviceability limit states that are likely to affect the structure. Ultimate limit states are those that will lead to failure of the ground or the structure; serviceability limit states are those that result in unacceptable levels of deformation, vibration, noise, or flow of water or contaminants (for example).
Eurocode 7 identifies five ultimate limit states for which different sets of partial factors are provided: failure or excessive deformation in the ground (GEO) and internal failure or excessive deformation of the structure (STR) are discussed at length in Chapter 6. Loss of static equilibrium (EQU), loss of equilibrium or excessive deformation due to uplift (UPL), and hydraulic heave, piping, and erosion (HYD) are discussed in Chapter 7.
The following ultimate limit states should be checked for all geotechnical structures: loss of overall stability (of the ground and/ or associated structures); combined failure in the ground and structure; and structural failure due to excessive ground movement.
The following serviceability limit states should be checked for all geotechnical structures: excessive settlement; excessive heave; and unacceptable vibrations.
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