Keller Grundbau has been successfully using the Soilfrac® process for the minimisation of settlements when constructing tunnels and for the remediation of tilting buildings for decades.

Returning leaning structures into a vertical position are spectacular technical challenges since efforts have been made for the leaning tower of Pisa – even with us. It is often the case however that a partial restoration is sufficient to regain the functionality and the aesthetic impression of a structure.

The Soilfrac®  process for minimising settlements during tunnelling
The Soilfrac® process for minimising settlements during tunnelling

The Soilfrac® process

With this process, sleeve pipes are initially inserted into the area of the soil that is to be treated. A packer that is at the end of a flexible grout hose injection line can then be inserted in the sleeve pipe up to a desired single valve before a defined injection volume is pressed through this valve.

This process is repeated in numerous injection phases, enabling targeted lifting to be carried out after completion of a pre-injection and a tensioning of the soil. With this process, fractures are created in the soil (fracs) which are filled with hardening grout. Every soil formation can be improved by multiple rounds of grouting and controlled lifting can be induced. 

The Soilfrac® process is used for the remediation of  foundations where ongoing settlements have to be stopped, where natural or man-induced deformations occur, where mining activities cause problems, where insufficient bearing capacities are found or sections of a structure have to be lifted.


Benefits of the Soilfrac® process

  • targets lifting of structures or structure parts for remediation after settlement damage has been caused
  • precautionary in order to minimise settlements resulting from tunnel construction work or increased loads, for example

Information for design and execution

The protection of structures against settlements arising from tunnelling and mining activities is an important application of the Soilfrac®-Method. This technique was first used by Keller for a subway project in the Ruhr area of Germany in 1985.