The gravel stuffing columns according to the impact® process are produced by first pressing a sleeve tube with a special compaction head (approx. 35 cm) into the substrate up to the scheduled lowering depth (mäklergeführt) (Fig. 1a). The pipe is protected against the penetration of soil material on its compaction head. If the penetration resistance is too high, the insertion is supported by vibration.
In the second step, the envelope tube is filled with gravel or grit (preferable grain approx. 8/32 mm) via the mixing container mounted at the top of the hem tube as well as the mixed material container itself (preferably grain approx. 8/32 mm) (Fig. 1b). The envelope tube is then pulled by a certain amount, while at the same time the cavity below fills with gravel from the envelope tube (Fig. 1c). The gravel is compacted by vertical ramming with the specially formed compaction head, whereby the gravel penetrates into the surrounding ground (fig. 1d) and the adjacent ground is displaced sideways. The surrounding soil matrix is thereby compacted. The column diameter is therefore also determined by the stiffness of the upcoming soils. In horizons of lower stiffness, larger column diameters occur, conversely, smaller diameters are to be expected for stiffer soils. The layer-wise compaction and manufacturing process is repeated up to the final height of the column (Fig. 1e). Inhomogeneities in the building ground are compensated in this way.