Cracking the Caisson Puzzle for mega structures

Editorial / March 27, 2026

What could possibly connect the haunting calm of Silent Night, the stirring cadence of The Army Goes Rolling Along, the official song of the US Army, once so popular it sold 750,000 copies across wartime Europe, and the pioneering research of Dr. Gyan Vikash at Shiv Nadar University's Civil Engineering Department, which shapes the immense foundations beneath bridges, offshore rigs, and coastal megastructures?

The unlikely thread is the caisson.

The word traces its origins to a two-wheeled cart used to transport artillery ammunition during the First World War. The Army Goes Rolling Along, composed in 1908 by Brigadier General Edmund L. Gruber, himself a descendant of Franz Xaver Gruber, who wrote Silent Night in 1818, carries that martial lineage in its name. Today, the same term has travelled far from the battlefield, anchoring some of the most ambitious feats of modern engineering beneath land and sea.

A caisson foundation is a large, hollow structure, usually made of concrete or steel, that is sunk into soil or underwater to support heavy structures such as bridges and piers. Soil is removed from inside so it sinks to firm ground, then concrete is poured, creating a strong, stable base in challenging conditions.

Most of the time, they do their job unnoticed. But when powerful forces like earthquakes, waves, or repeated loading come into play, understanding how these foundations behave becomes a real challenge. Dr. Gyan Vikash offers a more straightforward approach to tackling this problem, using a model that is both easier to understand and just as accurate.

His work examines how caisson foundations interact with the soil around them when pushed from the side by forces such as wind or water, and how those forces are applied repeatedly, as during earthquakes.

Until now, engineers have often relied on a well-known method called the Bouc-Wen model. The model developed by Robert Bouc and Yen-Kuang Wen, uses an internal variable to capture memory effects, enabling engineers to model nonlinear behaviour in structures, materials, and dampers, especially under dynamic loads such as earthquakes.

While it works, it comes with a catch: it depends on several parameters that are difficult to interpret in real-world terms. In practice, that makes it harder for engineers to use actual test data to fine-tune the model. The new approach takes a different route, simplifying the process without losing the ability to capture what really happens underground.

Instead of trying to describe every detail at once, the researchers define two clear limits. One represents how the foundation behaves at the beginning, when everything is stiff and movement is minimal. The other represents what happens later, when the soil starts to give way and the structure becomes more flexible. The real behaviour lies somewhere between these two extremes, and the model smoothly moves from one to the other.

What makes this approach particularly appealing is that it relies on just four parameters. These describe how stiff the system is at the start, how it behaves after yielding, and how it transitions during loading and unloading. Unlike older models, these parameters are easier to measure and directly relate to physical behaviour, making the model much more practical to use.

Importantly, the model captures two key features that engineers care about. The first is nonlinearity, meaning the foundation's response does not increase in a simple, predictable way as the load increases. The second is hysteresis, which describes how repeated loading causes energy loss and permanent changes in the system. These effects are crucial when dealing with real-world conditions like earthquakes or storm surges.

This matters because failures of caisson-supported structures have been observed during extreme events such as earthquakes and tsunamis. Predicting how these foundations will behave under such stress is essential for designing safer infrastructure. By reducing the model's complexity while maintaining its accuracy, the study provides engineers with a more accessible tool for making those predictions.

The potential uses of this model go beyond caissons. Similar behaviour is observed in other foundation types, including suction caissons and monopiles used in offshore wind turbines. With some adjustments, the same approach could be applied to a wide range of engineering problems involving soil and structures.

In the bigger picture, this research is a reminder that simpler can sometimes be better. By stripping away unnecessary complexity and focusing on what truly matters, the study makes advanced modelling more approachable. That, in turn, could help engineers design structures that are not only efficient but also more resilient in the face of increasingly demanding environmental conditions.