Novel Technology in High-pressure Jet Grout Method
What is High-pressure Jet Grout Method?
It is a method that involves spraying cement milk at great pressure, which cuts and grinds the ground while mixing and stirring it with the sprayed cement. It is possible to avoid preexisting structures underground as well as operate in tight, enclosed spaces.
- Creates a pillar-shaped grout column underground
- Technology that originated in Japan
Injection monitor
- In addition to the rotating motion, an agitating motion is possible to create freeform shaped grouting columns (circular, fan, elliptical, grid, etc.)
- Efficiently improve only the desired area
Various monitors for various occasions
Jetting 15 degrees downwards is also possible
Flow path divider (FPD)
In conventional monitors, turbulent flow forms within the monitor device, which suppresses the power of the jet.
Bent-style monitors regulated such formation, but introduced new problems such as production cost and monitor size.
Implementing the FPD made possible the downsizing of the monitors as well as reducing its production time and cost.
Use of the FPD strengthens the core of the jet and increases its distance.
Photo
Negative image
Mechanism of the flow path divider
Upon analyzing the cross-sectional region of the stream of jet fluid without the flow path divider, the flow speed near the center was large, and this speed diminished as it neared the edges of the nozzle. In addition, any turbulent flow that formed increased in force as the liquid traveled across the x-axis.
Upon analyzing the cross-sectional region of the stream of jet fluid while using the flow path divider, the average flow speed was higher across a wider region of the section. In addition, any turbulent flow diminished in force upon entering the narrow flow region, which plays part in preventing the loss of flow speed near the edges of the nozzle.
Evaluating nozzle quality usign a profile measuring instrument
φ4.3㎜ nozzle evaluation data – before use
φ4.3㎜ nozzle evaluation data – after use
Swirl Air Cover
Surrounding the jet of cement milk with a coaxial stream of air is said to improve the power of the jet.
By swirling this stream of air, a stronger power of the jet as well as an increased efficiency in sludge draining was observed.
Swirling the stream of air increased the efficiency of grouting and sludge draining.
