The process of manufacturing cylindrical columns from a blend of ground material and cement by drilling the ground with a drilling machine and mixing the high-pressure cement grout with the ground by spraying it is known as the jet grout method. The soil-cement mixture is a cementitious chemical mixture and it causes serious increases particularly in the shear strength of the ground. To increase the effect of these mixtures made by high pressure injection, substances such as fly ash and sodium sulfate are added to the mixture.
Diaphragms and walls can be built underground with the other jet grout columns applied next to the well devoid of leaving any space in between, without setting the column made with the jet grout method, which is applied from the ground level of the well upwards. Geotechnical engineering deals with the study of soil behavior, and the design and investigation of natural and man-made soil structures. The mechanical and geometric properties of the columns to be formed by the jet grouting method depend on the soil parameters to be applied, the method by which the application will be made, and also on the variable parameters and method properties in these methods.
Advantages of Jet grouting
The advantages of Jet Grouting are the prospect to form consolidated columns with diameters ranging from 60 to over 300 cm, using small diameter boreholes; and the possibility to construct soilcrete around subsurface obstructions.
Another advantage is the use of compact and lightweight equipment. Being easy to be operated in confined spaces, the equipment enables operating in direct contact with the existing superstructures that have to be consolidated by the soilcrete columns.
Various techniques of Jet Grouting:
Jet Grouting includes an initial drilling phase followed by removal of the drill string and monitor at preset and steady rotation and speed and simultaneous injection of fluid(s) at high pressure. The areas of application of Jet Grouting technology are usually the underpinning, bottom plugs, waterproof diaphragm walls, and slope consolidation.
Jet Grouting techniques are usually classified into three categories based on the number of fluids used during soil mixing: two-fluid, single-fluid, and three-fluid jet-grouting:
- Single-fluid system: The single-fluid system uses grout as the cutting jet and to achieve cementation of the eroded soil. Once the design depth is reached, the underneath nozzle is closed and the drill rod and monitor are at the same time rotated and withdrawn.
- Two-fluid system: In this system, the water/cement mixture is enclosed within a shroud of compressed air. The result is a more effectual cutting of the soil. The diameters that can be obtained typically range from 80 to 250 cm. In the injection area, the commotion created by air in the waste spoil enhances the efficiency of its removal.
- Three-fluid system: In this system, the cement/water mixture is encased within a covering of compressed air. The result is a more effectual cutting of the soil. The diameters that can be obtained typically range from 80 to 250 cm. In the injection area, the turbulence created by air in the waste spoil enhances the efficiency of its removal.
Thus, Jet grout method is applicable to all floor materials. It has light and small equipment.