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The main principle of this technique is a high kinetic energy cement grout jet to break up the terrain, and then adding cement to provide it with compression and shear strength comparable to a concrete floor.
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Jet grouting is a procedure for the insitu construction of solidified ground of pre-determined shape, size and depth, to a designed characteristic (strength, permeability, flexibility). This solidified ground is known as Soilcrete.
Advantages
- A more predictable degree of soil improvement.
- A high level of permeability control.
- Geometric flexibility.
- Improved cost forecasting over alternative processes.
- Minimal vibration and noise.
- Ability to operate in headroom as low as 3.0m.
- Minimum site disturbance and limited working space required.
- Only environmentally acceptable grouts are used in the process.
- Installation beneath foundations from outside building.
- Encapsulation of obstructions including services.
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Jet grouting is a construction process using a high kinetic energy jet of fluid to break up and loosen the ground, and mix it with a thin slurry.
It is not truly grouting but rather a hydrodynamic mix-in-place technique producing a soil-cement material.
The concept first appeared in the late fifties in the United Kingdom. Single, double and triple jets carry the necessary hydrodynamic energy to break up and mix the soil with the slurry. It is suitable for mass treatment, linear treatment and inclusions, in soils of good to poor groutability.
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Terratest has been performing Jet-Grouting for over 15 years. It is therefore one of the pioneers in the business in Spain and also one of the most reliable companies for the job. Highly qualified personnel and equipment are required for this purpose due to the specific nature of the technique and the risks involved with using fluids - water, air, cement - at high pressure and flow speeds.
Given its versatility, Jet-Grouting is more and more widely used to solve foundation problems in construction projects such as:
* Fore-slabs for water-proofing the bottom of core walls
* Core walls used to control the water table
* Foundation underpinning
* Improvement of soft soils
* Embankment foundations
* Embankment consolidation
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By means of the TREVIJET system it is possible to obtain columns with the following diameters:
- 0,35 – 1,00 m by means of TREVIJET T1
- 0,60 – 1,00 m by means of TREVIJET T1/S
- 1,40 – 3,00 m by means of TREVIJET T2
Said dimensions and the mechanical features of the treated soil highly depend on the combination of several elements such as the nature of the soil, the applied pressure, the monitor’s rotation and extraction speed and the composition of the grouting mixture.
With the aim of optimising all these variables and obtaining the best technical productive result, Trevi developed and tested in several sites a whole set of drilling and grouting rigs characterised by a highly advanced technological content as well as advanced checking systems. In this way, it is possible to work with large-size equipment that are assembled on cranes for vertical treatments at remarkable depths, or small size drill rigs suitable for working in basements and in reduced areas in case of consolidations of pre-existing buildings and monuments.
Last but not least in importance, we must mention the application of the TREVIJET system in case of sub-horizontal treatments for preventive consolidation works of tunnels, before the excavation, in loose and un-cohesive soils.
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Injections are used for ground improvement. Existing voids like pores in gravel or in unconsolidated material are filled under pressure with a hardening material, in order to stabilise or seal the soil. Drilling is done with techniques suitable for the prevailing soil condition. Injections can be used for under-pinning buildings, as a security measure at driving of tunnels and galleries or to seal deep excavations or dams. The selection of the injection material depends on the soil condition and on the application. If injections are no longer possible due to the soil condition, the jet grouting technique (the so-called "High Pressure Injection" is applied.
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Compaction grouting uses higher pumping pressures and a stiffer grout to create a enlarged bulb at the point of exit, thus compacting the surrounding strata by compression and rendering the soil less permeable. This increases the bearing capacity of the soil. This technique is useful in correcting differential settlement and uplifting settled solid floors.
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