What is Jet Grouting?
Jet grouting is a highly specialized technique used to create an in-situ mass of cemented soil also called soil-cement. A drill rig advances a relatively small diameter (4-8 inches) jet grout tool to the bottom of the proposed treatment zone and injects fluid grout at high velocity. The drill tool is withdrawn and rotated at a constant rate as the grout erodes and mixes the surrounding soil to create a soil-cement column from the bottom elevation upwards.
Jet grouting techniques can be classified as either single system (utilizing grout only), double system (grout and air) or triple system (grout, water and air). Each system has unique advantages and selection of the jet grouting system is dependent upon project specific criteria. Malcolm’s proprietary MEGA-Jet grouting technique is a modified double fluid system that is capable of generating columns up to 18 feet in diameter. This modified double fluid system utilizes a specialized multi-chambered drill rod system to convey slurry grout and air to the jetting tool. A high velocity coaxial stream of slurry grout is shrouded within a sheath of high pressure air to mix and erode the in-situ soils. The highly sophisticated MEGA-Jet monitor utilizes a unique array of nozzles specifically designed to focus the injection media at a given radius in balance with the chosen flow rate, line pressure and fluid specific gravity.
The constant variables inherent to geotechnical construction do not allow for analytical determinations alone when considering jet grouting.
Full scale field tests or test sections in some form are a requirement for jet grouting works to verify assumed construction parameters and performance.
Quality assurance and control are an ongoing effort and the responsibility of the field technician. All checking of permanent materials received, field grout testing, and record keeping are monitored and recorded. The agreed upon drilling, grouting, and injection procedures are developed during the test section and then used in production columns.
A state-of-the-art automatic data acquisition system provides a real time record of all relevant construction parameters for each column installed, including depth, volume injected, operating pressures, and column diameters.
Benefits of Jet Grouting
- Effective within a wide range of soil types.
- Ability to drill through overburden soils and focus jetting energy discretely within the targeted improvement area.
- Ability to construct both large diameter columns for mass stabilization and small diameter columns for underpinning.
- Can be installed at inclinations to overcome obstructions or access constraints.
- High strength, low permeability subsurface elements in specifically targeted areas.