Managing risk and achieving reliable geotechnical designs using Eurocode 7 - Risk and Reliability in Geotechnical Engineering - page 413

Table 10.8 Recommended partial factor values in Eurocode 7 for EQU, UPL, and HYD ultimate limit
states in persistent and transient design situations

Parameter Factor EQU UPL HYD

Partial factors on actions ( γ F ) or the effects of actions ( γ e )
Permanent unfavorable action 1.1 1.0 1.35 γ G;dst

Permanent favorable action 0.9 0.9 0.9

γ G;stb

Variable unfavorable action 1.5 1.5 1.5

γ Q;dst

Variable favorable action 0 - - γ Q;stb

Partial factors for soil parameters ( γ M )
Angle of shearing resistance
(this factor is applied to tan φ ')

1.25 1.25 -

γ tan φ ′

1.25 1.25 -

Effective cohesion c ′

γ c ′

Undrained shear strength c u 1.4 1.4 - γ cu

Unconfined strength q u 1.4 - -

γ qu

1.0 - -

Weight density of ground γ γ γ

Tensile pile resistance - 1.4 -

γ s;t

Anchorage - 1.4 -

γ R

Eurocode 7 in Sets A1 and A2, M1 and M2, and R1, R2, R3, and R4 that are combined
in different ways, referred to as Design Approaches 1, 2, and 3 (DA1, DA2, and DA3),
as shown by the columns of partial factors in Table 10.7 . These three Design Approaches
enable partial factors to be applied either to soil parameters (DA1, Combination 2, and
DA3) or to resistances (DA1, Combination 1, and DA2) for different design situations and
allow partial factors of unity to be applied to permanent loads in geotechnical design (DA1,
Combination 2, and DA3).
The recommended partial action, material, and resistance factors for use in EQU, UPL,
and HYD ultimate limit states, which are when there is loss of equilibrium due to destabiliz-
ing actions exceeding the stabilizing actions when the strength of structural materials and
the ground is insignificant, or failure due to uplift by water pressure or due to seepage pres-
sure, are shown in Table 10.8 . While in many design situations it is evident which ultimate
limit state controls, in principle all limit states should be checked.
Two design examples are provided in the following sections. The first example, Example
10.2, shows the determination of the design soil resistance on the side walls of a buried
structure against uplift, which is a situation where the conservative value of the earth pres-
sure is an upper value rather than a lower value. The second example, Example 10.3, is the
design of the buried structure against uplift, which is a design situation controlled by the
UPL partial factors.

10.4.4.2 Example 10.2: Determination of the design soil
resistance on walls against uplift
The buried structure shown in Figure 10.6 has a depth D = 6 m and overall horizontal
dimensions of B = 8 m and L = 10 m. The groundwater level is at the surface. The soil is sand
with a mean ϕ′ value of 30° and a weight density of 18 kN/m 3 . The purpose of this example
is to determine the design value of the frictional resistance on the side walls of the buried
structure against uplift.