Jet Grouting is method of ground improvement that departs from the classical forms of grouting in that it does not penetrate the soil either by means of impregnation or ‘claquage’, rather it uses high energy in the form of a high velocity jet of grout to destroy the soil structure and simultaneously mix cement grout into the in-situ soil. The principal purposes for the application of Jet Grouting are for significantly increasing the strength of the soil treated, reducing the permeability of the soil and the treatment of ground, where other methods of grouting simply are unsuitable.
The method involves drilling a hole to the design depth of the treatment, whilst maintaining an annular space around the drill string to facilitate return flow. Grout at high pressure is pumped to the bottom of the drill string where it emerges though a very small diameter orifice, converting the energy from high pressure to very high velocity. To form columns of treated ground, the drill string is rotated as the hydrodynamic jet of grout cuts and disintegrates the soil and mixes into it.
The distinct advantage of jet grouting is that it can be effective in all categories of soil, unlike classical grouting techniques which rely on penetration via voids in the soil mass.
Applications of Jet Grouting are several and varied, it can be used in retaining systems, to form cut-off barriers, as plugs for the bases of shaft excavations, in transition zones in tunneling, in underpinning and to create rigid soil inclusions. The essential merits of Jet Grouting are to increase strength and/or impermeability in soils.