Foundations slab depth

Depth of Slab. The thickness of the foundation slab (bottom course) required for punching shear must also be sufficient to withstand the tendency to shear along line (Z-Z2), (Figure ll-4c) at the edge of the pedestal. This shearing load may be determined as follows ... 

Foundation slabs or strap footings are structures which produce the deformation of a volume of terrain with dimensions of the same magnitude as the width of same. In the area of Ensanche de Vallecas where the position of the rocky layer can be found at depths varying from 15 to 30 metres, the layer of clays situated on the rock is within the active zone of the slab deformation. 

This paper describes a design procedure for direct continuous foundation (slabs and footings) in clayey terrain with cavities and karstic phenomena situated at a certain depth. 

Stemwalls, also called frost walls, are below-grade foundations that support the load of the abovegrade walls and thereby the roof. There is usually a footing beneath them at some depth below the frost line. The major radon-related issue for these walls is the geometry of the slab/stemwall joint. This will be covered in the section on floors. If stemwalls are constructed of concrete blocks, then the block tops should be sealed. 

The techniques necessary for placing concrete depend upon the type of member to be cast, namely whether it is a column, a beam, a wall, a slab, a foundation, a mass concrete dam, or an extension of previously placed and hardened concrete. For beams, columns and walls, the forms should be well oiled after cleaning them, and the reinforcement should be compacted and thoroughly moistened to about 6" depth to avoid absorption of the moisture present in the wet concrete. Concrete should always be placed in horizontal layers which are compacted by means of high-frequency power-driven vibrators of either the immersion or external type as the case may need. It must be kept in mind, however, that over-vibration can be harmful since it could cause segregation of the aggregate and bleeding of the concrete. 

---