The existing soil can especially be subsequently strengthened with compaction grouting in cases where existing structures need to transfer higher loads into the soil as a result of additional storeys or other extensions. It is also possible to repair damage, reduce, stop or even reverse foundation soil-related settlements.
The compaction grouting
When applying the compaction grouting process usually a stiff to plastic grout is injected into the soil under pressure. It expands in the soil as a relatively homogeneous mass and at the same time forms almost ball-shaped grout bulbs. The soil surrounding the grouted area is displaced and at the same time compacted. Compared to other grouting techniques, the grout material neither penetrates into the pores of the in-situ soil (as is the case with the classical injection) nor are local cracks formed (as is the case with the The Soilfrac® technique).
During the compaction grouting process pressure and grout quantity as well as possible deformations at ground surface, respectively at structures are monitored. Depending on the design requirements, the compaction grouting process will be terminated either when reaching a maximum pressure, a maximum grout volume, when achieving the desired uplift of the structure or in case of grout material flowing out on the site surface.
The execution method of the compaction grouting process is laid down in the European Standard EN 12715. The compaction grouting method may be used for the improvement of non-cohesive soils, especially in cases, where soils of loose to medium density are encountered.
This method is also used in fine-grained soils*) in order to install elements of higher strength and bearing capacity in soils of low bearing capacity, thus improving the load bearing behaviour of the soil.
Benefits of compaction grouting
- low-vibration creation
- execution under existing structures is possible
- simple manufacturing and quality monitoring
Information for design and execution
When using this technique in saturated clayey soil, a temporary increase of the pore water pressure can be observed.