Define pressure bulb in soil mechanics?

Shape: The pressure bulb is typically depicted as a three-dimensional shape, often resembling an inverted cone or pyramid. It extends downwards from the base of the loaded area or foundation into the soil.

Distribution: Within the pressure bulb, the pressure is not uniformly distributed. It is highest at the base of the loaded area and decreases with depth. The pressure distribution is influenced by factors such as the shape and size of the foundation, the load magnitude, and the properties of the soil.

Depth: The depth of the pressure bulb varies depending on the characteristics of the foundation and the soil. Deeper foundations will have deeper pressure bulbs.