Building a Caisson : How Deep Foundations Take Shape

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Building a Caisson: How Deep Foundations Take Shape

In this video, workers are constructing the first stage of a reinforced concrete caisson—a critical technique for creating stable deep foundations in challenging soil or waterlogged environments. The process begins with a flat, ring-shaped concrete base (visible at the pit’s bottom) embedded with vertical steel rebar. These protruding rebar ends act as anchors, ensuring precise alignment when the caisson’s walls are built atop them.

Next, wooden formwork is assembled around the rebar to shape the caisson’s walls. Once concrete is poured into the forms, it will harden into a hollow cylindrical or box-like structure with a sharp, reinforced “cutting edge” at its base. This edge allows the caisson to sink vertically into the ground as workers excavate soil from inside. The heavy concrete walls provide the weight needed to drive the caisson downward, while the steel-reinforced design prevents collapse under soil pressure.

Caissons are essential for projects like bridge piers, offshore platforms, or underground reservoirs where traditional excavation risks cave-ins. By building the structure incrementally from the surface, this method avoids the dangers of deep, unsupported digging. After the caisson reaches bedrock or stable soil, its hollow core is filled with concrete, creating a solid, load-bearing column capable of supporting massive structures.

This video captures the blend of simplicity and precision in civil engineering: a timeless solution to building deep, durable, and safe foundations.