Open caissons

For open caissons, a structure is built on ground level that is subsequently excavated form the inside out. The actual floor of the structure is initially lacking. The structure sinks into the ground during excavation. For this it uses its structure's own weight, bentonite lubrication of the walls to decrease friction, and external (additional) ballast or a caisson jacks. This is a jacking device that uses groundanchors to pull the structure into the soil and corrects any slanting. It is a controlled process in terms of dimensions and tolerances. Depending on the height of the structure and, consequently, the depth to which it has to be sunk, the structure is built up in phases and excavated either in the wet or in the dry. The underside of the structure is fitted with a cutting shoe. When the structure has been sunk to the required depth the floor can be established either in the wet or in a dry pit.

Application

With this method, a structure is built in a traditional manner on the ground level or in a dry dock. This means that a construction pit and the related water-retaining facilities and, possibly, drainage are not necessary. The area around the caisson experience hardly any disturbance. This method allows positioning of structures up to large depths. Examples of potential applications include water catchment pits, rainwater basins and cellar structures.

Ambient factors

Low vibrations and low noise.
Relatively small space needed at ground level.
No construction pit or drainage necessary.

Pros and Cons

VSF has experience in engineering and execution of sinking open caissons.
The advantage is traditional construction method at ground level.
Hardly any disturbance to adjacent structures.
The structure may have to be heavier because of the necessary weight and forces during installation then necessary when in use.

Applicated

Name of project	Client
IJmuiden, Cellar Scale-pit Tata Steel	Visser & Smit Bouw