Caissons

Caissons (plural) are watertight chambers used in construction work performed below the water level or ground surface. These structures provide a dry environment for workers to build foundations, repair structures, or excavate material in otherwise inaccessible locations. There are various types of caissons, including box caissons, open caissons, pneumatic caissons, and floating caissons, each suited for different depths and soil conditions. They are essential in building bridges, piers, tunnels, and other large infrastructure projects. The caisson method has been critical in advancing construction technology enabling deeper and more complex construction feats and also often requires specialized equipment and trained personnel due to the challenges of working in a contained and potentially pressurized environment.

Caissons meaning with examples

• Engineers utilized pneumatic Caissons to build the foundations for the new bridge, allowing workers to dig deep into the riverbed and install the massive concrete supports. The pressurized environment within the caisson prevented water from flooding the worksite, ensuring a dry and safe working condition. Once the caisson was completed, it was filled with concrete and now forms the footings of the structures that the bridge rests on.
• During the construction of the underwater tunnel, open Caissons were used to create temporary excavations, so the tunnel could be laid. These Caissons were sunk and then dredged out, allowing for the removal of material. As workers dug within the caisson, the walls protected them. The method minimized soil movement and allowed for precise alignment. The water was pumped out of the caisson so that it was safe to work in.
• The old dock was collapsing, so contractors used box Caissons to repair the pier. They constructed the large concrete Caissons off-site, floated them into position, and then sank them to the required depth. These Caissons formed the new supports for the dock's structure. This method enabled efficient and sustainable repairs without requiring significant dewatering or extensive underwater work to the pier.
• The team deployed a floating caisson to install a new intake pipe for the power plant, anchoring the structure in place, before the pipe laying took place. The large hollow chamber served as a stable platform for the work crew and provided protection from wave action, and the harsh marine environment. Using this system proved both time-effective and cost-effective, given the conditions and overall logistical needs.