What type of foundation is described as having a depth shallower than its width?

A foundation that has a depth shallower than its width is known as a shallow foundation. This type of foundation is typically used when the soil near the surface has adequate bearing capacity to support the loads from the structure. Shallow foundations are usually placed at a depth that is less than the width of the foundation, which allows for efficient transfer of loads to the ground and is often easier to construct. This design makes them suitable for lighter structures or where the soil conditions allow for a strong, stable base close to the surface.

In contrast, deep foundations, which go deeper into the ground to reach more stable substrate, are applicable in situations where surface soils are weak. Spread foundations, a specific type of shallow foundation, distribute load over a larger area but do not define a relationship of depth to width as explicitly. Pier foundations involve vertical columns or shafts that transfer loads deeper into the ground but are categorized as deep foundations. The focus on the relationship of depth and width clearly indicates that the correct classification is indeed a shallow foundation.