Compaction grouting is a technique in which a stiff to plastic grout is injected into the soil under pressure. It expands in the soil as a relatively homogenous mass and at the same time forming 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 classical injection) nor are local cracks formed (as is the case with the Soilfrac® technique). During the compaction grouting process, the following 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 of in case of
grout material flowing out on the site surface.
The
compaction grouting method may be used for the improvement of
non-cohesive soil, 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. This improves the load bearing behaviour of such
soils. When using this technique in saturated clayey soil, a
temporary increase of pore water pressure can be observed.
(Due to the fact that fine-grained soils cannot be compacted
from the soil mechanics point of view- by applying the same
technique- strictly speaking, “consolidation grouting” is
carried out.)
The degree of compaction can be
controlled by the following parameters:
• Evaluation of the automatically recorded process parameters by means of Keller's in-house software
• Deformation measurements at ground surface or structures
• Soundings (CPT, SPT) before and after the compaction grouting process The installation process may be summarized as follows:
