1.  Field of the Invention
This invention relates to a process for lowering into the ground building structures, such as shutdown nuclear power plants or building structures to be erected as they are lowered, wherein a caisson having a top plate for supporting the building structure is provided below the bed plate of the building structure and is lowered in steps together with the building structure. 
2.  Description of the Prior Art
A process of the above kind for lowering nuclear power plants or reactor parts of nuclear power plants is disclosed in German Patent Specification No.  28 54 330. 
In the lowering of building structures together with caissons, the ground within a space defined by the top plate and the cutting edge rings of the caisson generally is excavated until the caisson subsides under the weight of the building.  A lowering step is effected when sufficient soil has been excavated that the pressure applied to the caisson overcomes frictional forces acting on the outside surfaces of the cutting edges, the bearing reaction acting on the cutting edges and the internal pressure in the caisson, which internal pressure may be a hydrostatic pressure or pressure applied by compressed air to displace underground water.  This means that the caisson will descend at times which cannot be exactly predetermined and by varying distances when sufficient soil has been excavated such that the caisson can descend. 
Such uncontrolled descent of the caisson is not desirable when building structures which are, e.g., 60 meters in diameter, are to be lowered. 
For this reason it is an object of the invention to provide a process of the kind described which can be used for controlled lowering of building structures by predeterminable distances.