Geotechnical design by calculation (Foundation)

Last modified by Fredrik Lagerström on 2021/06/02 15:41

Design values of geotechnical parameters

According to EN 1997-1 2.4 the design values is calculated in the following way:

X_d = X_k / γ_M

γ_M are partial factors according to EN 1997-1 Annex A.

X_d = η X_k / γ_M

η is a factor considering uncertainties relating to properties for the earth defined by the user. See [3] 3.2.3. To consider this the defined characteristic value should be according to EN 1997-1.

γ_M are partial factors according to EN 1997-1 Annex A.

Ultimate Limit State

According to EN 1997-1 2.4.7 five types of ultimate limit states are possible. For spread foundations the following three types are relevant:

(EQU) Loss of equilibrium of the structure considered as a rigid body, in which the strength of structural material and the ground are insignificant. This case will be used for foundation on rock or very firm earth material.

(STR) Internal failure or excessive deformation of the structure in which the strength of structural materials is significant in providing resistance.

(GEO) Failure or excessive deformation of the ground, in which the strength of soil or rock is significant in providing resistance, e.g. overall stability and bearing resistance of spread foundations.

Design Approaches

According to EN 1997-1 2.4.7.3.4 and Annex A one of three Design Approaches should be used.

EC Standard