Pneumatic Caissons

For caissons, a concrete structure is built at ground level, with wedge like cutting shoes created underneath. These are approx. 2 metres high, so people can work underneath the floor of the structure after completion during sinking. The caisson sinks by removal of the soil with water cannon and sand pumps. The soil/water mixture  this produces is removed by means of hydraulic soil transport. When the water table is reached underneath the caisson, increased air pressure is applied to be able to continue working in the dry. Staff must enter and exit through an air lock. Caisson legislation dictates stringent safety requirements for staff. The caisson is accurately positioned at the required depth using bentonite lubrication along the walls and internal or external ballast all depending on the size and shape of the structure. Once the required depth has been reached, the work area is filled with concrete to complete the foundation of the structure.   A presentation of this technique (film of approx. 17 min.) on pneumatic sinking of caissons for the Lock in IJmuiden you can see  to click on the link below.  Click here for the start of the film. For questions and application options about this and other techniques, please contact VSF.