Jet Grouting Construction Method
This method describes the selection of machinery, equipment, materials, preparation, application, and quality-control procedures required for jet grouting works.
All production shall comply with TS EN 12716 – Special Geotechnical Applications: Jet Grouting.
1. Site Preparation
The construction area must be level, compact, and kept dry for efficient machine operation. Proper drainage must be installed, and groundwater and drilling spoil must be removed continuously. Heavy equipment must operate without sinking more than 10 cm.
2. Soil Information
Execution techniques follow the geotechnical investigation reports.
3. Environmental Information
Underground/surface obstacles (utilities, steel, concrete) shall be officially identified and removed by the employer.
4. Column Layout & Tolerances
Jet grout locations are set out by professional survey teams.
All columns must remain within 75 mm of the design center.
Vertical deviation must not exceed 1/50.
Construction parameters (pressure, flow rate, rotation, lifting speed) are determined through test columns.
Adjacent drilling must not proceed within two column diameters for at least 24 hours.
5. Jet Grout Column Production
5.1 Definition
Jet grouting forms soilcrete columns by injecting a high-pressure water-cement mix at 300–600 bar (typically 400–450 bar).
The mix exits the nozzles at speeds up to 250 m/s, cutting the soil and mixing with it to form a cemented soil mass.
Column quality depends on:
• Soil type
• Injection pressure
• Flow rate / nozzle size
• Grout mix
• Rotation & lifting speeds
5.2 Drilling
Drilling uses appropriate bits depending on soil hardness.
Fluids such as water, air, bentonite slurry, or grout may be used for cooling and cleaning.
Drill rods and connections must withstand 600–700 bar.
5.3 Injection
At the target depth, drilling stops.
A steel ball redirects grout to the monitor carrying 2–4 nozzles.
Grout W/C ratio ≥ 0.70.
High-pressure injection begins, forming a circular section as the tool rotates and is pulled upward at constant speed.
Top of the column must remain 30 cm below surface to avoid damage.
6. Production Methods
6.1 JET1
Single-pipe system; only grout is injected at high pressure.
Column diameters: 600–1200 mm, depending on soil.
6.2 JET2
Double-pipe system; grout + compressed air (8–12 bar).
Produces 60–80% larger diameter than JET1.
7. Materials
• Cement: Portland cement per project specification
• Water: Clean, sediment-free
• Additives: Used if required
8. Machinery & Equipment
• Jet grouting rig
• High-pressure grout pump
• Automated mixer & storage tank
• Cement silo + conveyor
• Water tanks (15–25 tons)
• Compressor (8–12 bar), welding machine, 50 kVA generator
Equipment must allow prewashing if required to prevent soil heave or to achieve design diameter.
9. Reporting
Daily records are kept per TS EN 12716, including:
• Date & reference no.
• Column depth & length
• Nozzle type & diameter
• Drilling tools
• Rotation & lifting speeds
• Soil type
• W/C ratio, cement type & quantity
• Special notes
10. Quality Control
Production and materials are inspected according to QC procedures YY.09 and material acceptance standard T06.