Jet grouting is a grouting technique that creates in situ geometries of soilcrete (grouted soil) using a grouting monitor attached to the end of a drill stem. The jet grout monitor is advanced to the maximum treatment depth at which time high velocity grout jets (and sometimes water and air) are initiated from ports in the side of the monitor. The jets erode and mix the in situ soil as the drill stem and jet grout monitor are rotated and raised.
Depending on the application and soils to be treated one of three variations is used: the single fluid system (slurry grout jet), the double fluid system (slurry grout jet surrounded by an air jet) and the triple fluid system (water jet surrounded by an air jet with a lower grout jet). The jet grouting process constructs soilcrete panels, full columns, or anything in between (partial columns) with designed strength and permeability. Jet grouting has been used to underpin existing foundations, construct excavation support walls, and construct slabs to seal the bottom of planned excavations.
Jet grouting is effective across the widest range of soil types of any grouting system including silts and most clay. Since it is an erosion-based system, soil erodibility plays a major role in predicting geometry, quality, and production. Cohesionless soils are typically more erodible by jet grouting than cohesive soils. Since the geometry and physical properties of the soilcrete are engineered, the properties of the soilcrete are readily and accurately predictable.
Jet grouting’s ability to construct soilcrete in confined spaces and around subsurface obstructions such as utilities, provides a unique degree of design flexibility. Indeed, in any situation requiring control of groundwater or excavation of unstable soil (water-bearing or otherwise) jet grouting should be considered.
Usually, jet grouting can be accomplished without disrupting normal facility operations. The recent development of small, containerized, highly mobile support equipment has enabled starting jet grouting work on the first day of setup, greatly reducing mobilization and demobilization costs. Jet grouting can often result in construction schedule savings.