Ground slabs - Slab bending

When there is foundation movement because of reactive soils, the slab will bend. The resulting movement is classified as either dishing or doming. The type of bending will determine where steel reinforcement needs to be placed in the concrete slab.

A ground slab may experience dishing in very wet conditions. The soil expands with the extra moisture which exerts stress on the slab.

Diagram of dishing occurring to a slab.

A ground slab is most likely to experience doming. As the sun dries the soil, moisture moves under the slab and creates an area of soil expansion.

Diagram of doming occurring to a slab.

Doming of a slab results in tensile stress in the upper surface of the slab. This means that the steel reinforcement should be placed in the upper area of the slab.

Diagram showing the tension and compression. Steel reinforcement is placed in the upper area of the slab.

Stresses are reversed for the dishing slab, but as this is not a typical industry case it is not covered here.