The use of slurries in order to avoid the hydraulic cutting of ground was first used in 1948 by the petroleum and natural gas industry. Later, the application of hydro-jets of high velocity was used in underground works for cutting soils and rocks.
Jet Grouting (JG) consists of injecting water under very high pressures typically of 200-600 atm through tiny nozzles of 1-2mm. The resulting water jet has a very high velocity and acts as a solid body transferring a very high concentrated energy. This energy can be adjusted by changing the size of the nozzles or the supply.
This technique constructs soilcrete columns with shapes that depend also on ground conditions and that can achieve designed strength and permeability. JG can be used to improve ground characteristics, to underpin existing foundations, to seal the bottom of planned excavations and other.
Depending on the design requirements and ground conditions, three options are available: the single system (slurry grout jet), the double system (slurry grout jet surrounded by compressed air) and the triple system (water jet surrounded by compressed air, with a separate grout jet).
A main difference from other grouting techniques is that JG can be applied to treat most types of soils, from soft clays to sands and to gravels. As it can be adapted to various ground conditions it provides a lot of flexibility to both designer and contractor. Based on the above JG should be considered in any project requiring excavation of unstable soil or control of groundwater.
GT GROUND ENGINEERING & CONSTRUCTION SERVICES has been involved in several application of this method especially in the port environment. Recent application include (i) double system JG was used for the stabilization of port fill under a 200m long pier and (ii) single system JG was used to construct soilcrete columns which in combination with bored piles were used for the underpinning of a pier in order to accommodate larger ships.