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# Bearing Pressure Calculation

How is the bearing pressure calculated beneath the base in the retaining wall module?

The program checks the stability for overturning of the wall by assuming rotation about the lower
front corner of the base. If a shear key is used and it is located within one quarter of base width
from the front, the program also checks for rotation about the bottom of the shear key, and then
uses the worst case. The program indicates the point of rotation with a circle either around the
front corner of the base or the bottom of the shear key as illustrated in the images below:

Eccentricity:

The point of action of the resultant force (XR) is calculated by summing all the horizontal and
vertical forces acting on the retaining wall about the rotation point and then dividing by the vector
sum of the vertical forces:

Mr: Stabilising moment at serviceability limit states ((kN.m)

Mo: Destabilising moment at serviceability limit states (kN.m)

Pv: Vector sum of vertical forces at serviceability limit states (kN)

XR : Point of action of the resultant force (m)

The eccentricity of the resultant force from the centre of the base is then calculated:

B: Total length of the base (m)

e: Eccentricity of the resultant force (m)

• Calculation of the stabilising and destabilising moments are shown within the retaining wall
calcsheet and helpfile

Bearing Pressure:

The location of the resultant force is then used to determine the minimum, θmin, and maximum,
θmax, bearing pressures acting on the base of the retaining wall. The following conditions are used to
determine the bearing pressures: