Urp

dw = — for H < 4m, dw = 1m for H > 4m where H is the wall's retained height.

12.3.4 Wall friction and adhesion

Eurocode 7 Part 1 states that the amount of wall friction and adhesion mobilized depends on the ground's strength, friction properties of the wall/ground interface, direction of wall movement relative to the ground, and the wall's ability to support vertical actions. [en 1997-1 §9.5.1(4)]

The design angle of wall friction 5d may be taken as:

Sd = k XPcv,d where ^cv,d is the design value of the soil's constant volume angle of shearing resistance. For steel sheet piling supporting sand or gravel, k = 2/3 and, for cast-in-place concrete walls, k = 1. [en 1997-1 §9.5.1(6) and 9.5.1(7)]

Eurocode 7 does not give any advice regarding suitable values of wall adhesion to use in design. The absence of wall adhesion from the expressions for earth pressures given in Annex C of EN 1997-1 suggests wall adhesion should be ignored - although the UK National Annex has 're-introduced' wall adhesion into these equations (see Section 12.4.4 below).

Values of wall friction may be less than the equation above suggests, particularly when the wall carries large vertical loads or coatings are applied to the wall surface. It is common practice to ignore wall friction and adhesion in such circumstances (or even apply negative values of wall friction, for example when extremely high vertical loads are applied to the wall). The wall should be checked for vertical equilibrium to confirm an appropriate value of wall friction has been used (especially for sheet pile walls which have limited base resistance). [en 1997-1 §9.7.5(4)P]

The table below compares the recommendations for wall friction given in Eurocode 7 with those from traditional practice.

Publication

Surface

Wall friction tan 5

Publication

Surface

Wall friction tan 5

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