Compensation Grouting Process
The Compensation Grouting Process (CGV) is a construction process for building security, in which the foundation area of structures is stabilized by injections in order to compensate for the subsidence caused by tunneling. The Compensation Grouting method is used, for example, when driving shields in urban areas. Among other things, it was used in the construction of the Leipzig City Tunnel .
functionality
For the ground injection, shafts must be created that are deeper than the buildings to be secured. From these shafts, fan-shaped valve pipes are drilled horizontally under the building, so that you can work in a targeted manner in a grid. Then, as a rule, special suspension is pressed into the soil in several phases through the valve tubes:
- Contact and stabilization injection: In the first phase, the soil tensions by filling up the pore spaces.
- Lifting injection: more concrete is injected and breaks the first injection ( fracking ). This increases the volume and creates a protrusion that pre-compensates for settlement to be expected later.
- Settlement compensation: During the actual shield drive, further injections are carried out to compensate for new settlements. The buildings are carefully monitored using measurements.
- Follow-up injection: After the shield drive has been completed under the building, any subsequent subsidence will be compensated.