6.5 Ultimate limit state design

6.5.1 Overall stability

(1)P Overall stability, with or without the foundations, shall be checked particularly in the following situations:

  • near or on a natural or man-made slope;
  • near an excavation or a retaining wall;
  • near a river, a canal, a lake, a reservoir or the sea shore;
  • near mine workings or buried structures.

(2)P For such situations, it shall be demonstrated using the principles described in Section 11, that a stability failure of the ground mass containing the foundation is sufficiently improbable.

6.5.2 Bearing resistance General

(1)P The following inequality shall be satisfied for all ultimate limit states:

Vd ≤ Rd

(2)P Rd shall be calculated according to 2.4.

(3)P Vd shall include the weight of the foundation, the weight of any backfill material and all earth pressures, either favourable or unfavourable. Water pressures not caused by the foundation load shall be included as actions. Analytical method

(1) The sample analytical calculation for bearing resistance given in Annex D may be used.

(2)P An analytical evaluation of the short-term and long-term values of Rd shall be considered, particularly in fine-grained soils.

(3)P Where the soil or rock mass beneath a foundation presents a definite structural pattern of layering or other discontinuities, the assumed rupture mechanism and the selected shear strength and deformation parameters shall take into account the structural characteristics of the ground.

(4)P When calculating the design bearing resistance of a foundation on layered deposits, the properties of which vary greatly between one another, the design values of the ground parameters shall be determined for each layer.

(5) Where a strong formation underlies a weak formation, the bearing resistance may be calculated using the shear strength parameters of the weak formation. For the reverse situation, punching failure should be checked.

(6) Analytical methods are often not applicable to the design situations described in (3)P, (4)P and (5). Numerical procedures should then be applied to determine the most unfavourable failure mechanism.

(7) The overall stability calculations described in Section 11 may be applied. Semi-empirical method

(1) The sample semi-empirical method for bearing resistance estimation using pressuremeter test results given in Annex E is recommended. Prescriptive method using presumed bearing resistance

(1) The sample method for deriving the presumed bearing resistance for spread foundations on rock given in Annex G is recommended. When this method is applied, the design result should be evaluated on the basis of comparable experience.

Eurocode 7 Geotechnical design Part 1 : General rules