Jet Grouting is a unique and highly innovative drilling and grouting technology used to create - in situ - large diameter soil/cement columns using small diameter drill tooling. The three principal jet grouting methods are classified by the number of fluids employed: single fluid, double fluid and triple fluid, representing, respectively, cement grout, cement grout and air, and cement grout, air and water. Soil/cement columns are created during drill rod retraction. Specialized drill rods, manufactured to carry the various jet grouting fluids independent of one another to the tip of the drill string, are installed to depth using conventional rotary drilling methods. Upon commencement of jet grouting, the drill stem is rotated and retracted with the jet grout fluid(s) being injected under very high pressures and flow rates. The high energy jetting action achieves large diameter soil/cement columns through erosion, displacement and mixing of the injected grout with the in situ soils.
Column size is dependent on soil type, soil density, injection pressures and flow rates of the various fluids employed, rotation speed, lift rate and type of system used. Due to the number of parameters that contribute to column size, it is standard practice to install and subsequently sample or exhume several test columns to calibrate and adjust the jet grouting parameters and design.
Typically, jet grouted columns are constructed in an array or sequence of some kind to provide an improved soil mass. Geo-Foundations has completed more than a dozen jet grouting projects using the double fluid system (cement grout jacketed in air). These projects involved the consolidation and strengthening of water-bearing, cohesionless native soils ahead of excavation by tunnel boring machine, as well as in situ construction of deep hydraulic barrier walls. Other jet grouting applications include underpinning, slope stabilization and excavation support.