Jet Grouting is the high pressure injection of a cementicious grout slurry into a soil strata to hydraulically mix the insitu material with grout. The resulting amended soil material is called " soil-crete ".
The most common technique used in Jet Grouting involves the insertion of the Jet Grout Pipe to design depth for the bottom of the soil-crete column. The pipe is typically a high pressure version of specialized drill rods with a hollow center and special Jet Grouting Nozzles at the tip. Next, the jetting pipe is rotated slowly and pressurized with a grout slurry made typically of portland cement and water. The high pressure ( 4000 - 6000 psi ) forces the grout out laterally through special ports located in the sides of the pipe, near the bottom. The slurry exits the jet port at very high velocity, impinges on the soil, penetrating it several inches to feet away from the jets. The rotating jets destroy soft soil formations, and intimately and uniformly mix the native soil with cement. Finally the rotating pipe is drawn slowly upward at a carefully controlled rate so that the jets create a nearly cylindrical column of treated soil. The actual diameter of the soil-crete column is dependent upon specific items; soil conditions, grout mix, nozzle diameter, rotation speed, withdrawal rate and grout pressure. Jet Grouting "recipes" should be tailored to each project considering the soil type and the application. Jet Grouted Columns may be interconnected to form cut off walls or structural sections.
Jet Grouting Nozzles
Single Phase Jet Grouting Process
Jet grouting is the high pressure injection of a cementacious slurry into a soil strata to produce a "soil-crete". The single phase Jet Grout method relies on the high velocity of the jet stream to cut, remove and mix the in-situ soil. One major advantage of Jet Grouting is that large diameter columns and walls can be created from a small diameter drill hole and subsurface obstructions or utilities can be by-passed or avoided.
DRILLING - to design depth is accomplished by water flushing through the bottom of the drill rods. The advantage of this method is that Jet Grouting may commence once the design depth has been achieved.
CHANGING OVER - from flushing to injection is accomplished by a special check valve located at the base of the drill rod. This will permit the lateral flow of grout slurry through the nozzles at full pressure.
INJECTION - A cement-bentonite slurry exits from the bottom portion of the lance under tremendous pressure and very high velocity. The soil is cut by the jet in a radial pattern as the lance is rotated. The rotation and withdrawal of the lance create a cylindrical column of "soil-crete". The grouted columns may be interconnected to for cut-off walls or structural sections.
EARTH TECH JET GROUTING UNIT
The entire unit is permanently trailer mounted to permit cost efficient mobilization and easy movement at the job site. A five cubic yard capacity, high speed slurry mixer supplies slurried mixtures of cement and bentonite for the Jet Grouting operation. The grout components are typically supplied to the project in 100 pound paper bags. The triplex piston pump is designed to deliver flow rates that vary from 30 to 300 gpm at pressures exceeding 13,000 psi.
Jet Grouting Unit
The control panel at the Operators Station monitors injection pressure with a calibrated gauge and flow rates with a digital readout. The injection pressure is regulated with an electronic override to prevent dangerous pressure spikes.
JET GROUTING TEST PROGRAM
Excavated Soil-Crete Columns exhibit different Jet Grout recipes
Interconnected Jet Grout Columns