Grouting is used in specialist foundation engineering to introduce the grout material (water with hydraulic binders and possibly additives) and solutions (soft gel, silicate gel) into the soil. A basic distinction is made between displacement grouting (compaction grouting, hydraulic fracturing) and grouting without displacement of the host material not involving ground displacement (permeation, fissure grouting, bulk-filling).
Suitable drilling rigs are used to execute spread bores from shafts beneath buildings, fill them with a sleeve grout and install the tubes-à-manchettes. By targeted injection of grout material into the tubes-à-manchette the soil is broken up and pretensioned. Controlled multiple grouting operations, with electronic uplift monitoring of the buildings compensate for settlement.
In the compaction grouting process a comparatively stiff, special mortar is pumped in stages from bottom to top into the mostly loose ground in order to compact it without breaking it up. Probes verify the success of the compaction grouting.
Permeation grouting enables deep-level sealing blankets to be produced in sand and gravel. Single sleeve pipes are vibrated into the ground or installed in bores in a preset grid configuration. Through the valve the grout is injected. In the vicinity of the valves spherical or elliptical grout bodies are created which form a continuous, tight blanket.
The jet grouting method is a specialist technique for underpinning, reinforcing or deepening building foundations, for sealing or stiffening blankets and for dam sealing. To produce jet grouting bodies a drill rod is drilled into the ground. When the specified depth is reached, an energy-rich liquid – water or water-binder slurry – is jetted through a nozzle at the bottom end of the rod. Simultaneous extraction and rotation of the drill rod causes the liquid jet to erode the soil. A portion of the soil is flushed out with the liquid. With the binder slurry remaining in the soil, a cylindrical plastic concrete body is produced.