Calculation of the resultants position

For Earth pressure against the failure surface the required ground pressure resultant in order to achieve equilibrium is calculated. A moment equation around origin with a vertical and horizontal equilibrium equation results in the position y₀, z₀ and the slope α₀ for the ground pressure resultant R₀ and its components V₀ and H₀. Two combinations are considered, with and without surcharge load Q on the back fill situated between the wall rear and the failure surface.

For Earth pressure against the wall the procedure is similar. The part of the back fill and the load on it is considered partly by the earth pressures P₁ and P₂  and partly by the parts of the resulting force R in the rear slip surface that will affect the slab.

From this the ground pressure can be calculated.

Vertical ground pressure

The vertical ground pressure is assumed to be uniformly distributed on the surface b × l where:

• l = length of retaining wall
• b = effective width
• b ≤ width of the foundation slabplattans totalbredd.

Bearing resistance capacity

The capacity is calculated according to [1] Annex D.

 Swedish Annex

The bearing resistance capacity is calculated according to [3] 4.3.1.3 eqv. 4.2 and [5] 2.42 and 3.42. For cohesionless soil the calculation is performed for drained conditions (cohesion parameter c = 0). For normally consolidated clay the capacity is calculated with the assumption of un-drained conditions (friction slope ϕ = 0) while for over consolidated clay and medium soil the calculation is made with regard to both drained and un-drained conditions. For rock allowed values can be found in [5] 3.42. The partial resistance factor γ_R;v considering uncertainties in the analytical model is predefined for design approach 3 (see above).