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Ann-Kathrin Dannwerth, B.Sc.

2024-07-11

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Sliding

Sliding design involves verifying whether the horizontal actions acting parallel to the foundation base can be sufficiently absorbed by the existing resistance.
There is a risk of sliding if the design value of the horizontal action is greater than the design value of the resistance to sliding. According to EN 1997-1 [1] 6.5.3, it is necessary to design a failure by sliding on the base area if the load vector is not perpendicular to this surface.

EN 1997-1: Sliding

Determination of Actions and Resistance
The governing action is the resultant horizontal force H_d at the foundation base. The resistance to sliding consists of the following components:

Friction resistance between the foundation base and the subsoil
Passive earth pressure, if applicable

In the drained state, the design value of the shear resistance is calculated using the design value of the friction angle:

R_{d} = {V^{'}}_{d} \cdot \tan δ_{d}

Shear Resistance in Drained State

In the unconsolidated state, the effective base area A' is calculated. The design value of the shear resistance is determined using the design value of the cohesion in the undrained state c_u,d:

R_{d} = A^{'} \cdot c_{u, d}

Shear Resistance in Undrained State

Optionally, passive earth pressure can be taken into account:

σ_{h, t} = k_{p, h} (γ_{d} \cdot z_{o b e n} + q_{d}) + 2 \cdot {c^{'}}_{d} \cdot \sqrt{k_{p, h}}

σ_{h, b} = k_{p, h} (γ_{d} \cdot z_{u n t e n} + q_{d}) + 2 \cdot {c^{'}}_{d} \cdot \sqrt{k_{p, h}}

Top and Bottom Horizontal Passive Earth Pressure

R_{p, x} = \frac{σ_{h, t} + σ_{h, b}}{2} \cdot t \cdot w_{x}

R_{p, y} = \frac{σ_{h, t} + σ_{h, b}}{2} \cdot t \cdot w_{y}

Resisting Force of Soil Layer in x- and y-Directions

Sliding Design
Sliding is designed by comparing the action and the resistance:

H_{d} \leq R_{s, d} + R_{p, d}

Sliding According to EN 1997-1 (Taking Passive Earth Pressure into Account)

References

European Committee for Standardization (CEN). (2014). Eurocode 7: Geotechnical Design – Part 1: General Rules, EN 1997-1:2014-03. Berlin: Beuth Verlag GmbH.

Parent Chapter

External Stability – Geotechnical Design