Jet-grouting – технологии

Jet grouting is based on soil stabilization by soil erosion and mixing it with a high-pressure jet of cement mortar. A result is a formation of the jet grouting piles with a diameter of 300 - 2500 mm, which are effectively used in the following directions:
- shoring of excavation and creation of retaining walls;
- soil stabilization of different types;
- subgrading with the reinforcing elements;
- vertical or horizontal water-repellent barrier of permanent and temporary use;
- soil stabilization when tunneling and laying roads;
- slope paving;
- soil stabilization at the basement of the projected foundations;
- filling of underground opening and karst cavities.

Unlike other technologies in this field, jet grouting makes it easy to equalize the strength and deformation properties of soils, as the reinforcing elements are added into the ground right during the cementing process. After that, the soil used in the Jet grouting technology and the jet grouting piles installed therein are concidered as a single geotechnical massif.

Production equipment.
A set of process equipment necessary for the production of jet cementation of soils using the Jet1 process variant includes the following:
- cementing pump of high pressure
- mixer station
- drilling rig
- silo for cement storage.

All the technology of the Jet grouting process must be performed in 2 stages: direct and reverse stroke of the drill string.

During the first stage, a leader well is drilled to the design mark; during the second stage, a cement mortar enters the nozzle of the monitor at the lower end of the drill columns, and the column begins to rise simultaneously with the rotation. Diameter of the jet pile depends on the pressure with which the cement slurry is pumped.

Three main technologies are also used:
Jet-1 (one-component system) uses a binder to break down the structure of the soil. The diameter of the "piles" is up to 900mm. The advantage is a simplicity in execution, a minimum set of equipment: mixing and pumping stations, a drilling rig with a set of equipment. While working on this technology drill rods are used, which have a single nozzle for supplying cement mortar.

Jet-2 (two-component system) differs from Jet-1 in that there is a jet of cement mortar under the influence of compressed air. This allows to increase a diameter of soil-cement piles up to 1700 mm. To produce the work, it is necessary to have a mixing and pumping station, an air compressor, a drilling rig with a set of equipment to produce works using Jet-2 technology, special drill rods with separate supply of cement mortar and compressed air.

Jet-3 (three-component system) allows to obtain columns of a larger diameter up to 2500 mm. In this system, soil structure is destroyed by a high-pressure water jet under the influence of compressed air. The ground is washed out with water to the surface, and the air makes it more efficient. The cement mortar is supplied by injectors located below the water and air supply nozzles. This technology requires separate pumps for cement mortar, water and air, special drilling stems with three channels.

The choice of a specific jet grouting technology must be made considering numerous factors, such as soil parameters, necessary dimensions and strength of the resulting soil-cement massif.

Technology