What is the term for a mass of solid reinforced concrete cast around the head of a group of piles?

The term that describes a mass of solid reinforced concrete cast around the head of a group of piles is known as a pile cap. A pile cap serves an essential purpose in structural engineering, as it distributes the structural load from the superstructure to the individual piles beneath it, ensuring stability and even load distribution. This component is crucial in situations where the soil conditions may not be able to support the loads imposed by the structure alone.

The pile cap effectively connects multiple piles, providing increased strength and stability, especially in applications involving larger buildings or bridges. It helps to minimize differential settlement and keep the piles aligned properly under varying load conditions.

In contrast, a foundation refers to the entire structure that supports a building, which may include several components such as footings, piles, and the pile cap itself. The term capstone typically refers to a finishing element on a wall or structure, and footing is generally a specific type of foundation element that supports individual columns or walls and is different from the context in which piles are used.