Ground–structure interaction

The jet grouting (DSV ) is a specialist foundation engineering processes to create cement - soil mixture bodies in the ground. This pending soil is mixed under high pressure with a cementitious binder suspension.

Other common, but not normative, labels are high pressure soil stabilization ( HDBV ), high pressure injection method (HDI ) method, jet grouting, and company-specific names like Soilcrete method.

Method

For the preparation of a DSV body injection lance is initially drilled into the ground. Usually in such a flushing -assisted wet drilling method used. After reaching the final depth a mineral binder suspension under high pressure at the tip of the lance into the ground injected ( pressures up to 600 bar, exit velocity > 100 m / s). The sharp beam intersects the surrounding soil material. In this case the soil is eroded and mixed with the binder suspension is then mixed with the natural ground as the additive a concrete-like body.

As a binder based on cement, a suspension is used, the still bentonite and depending on the requirements of various chemical additives may also be added. Although bentonite decreases the concrete strength, but causes already the fresh concrete is waterproof and the binder thus can not be washed, which is especially important flowing groundwater.

Depending on the method, the suspension is of a single nozzle injection ( simplex method ), a coated compressed air binder ray used ( duplex mode ), or the soil is cut with a jacketed with compressed air jet and the in vorerodierten in this way bottom binder with a low pressure injection ( Triplex process). Advantageous in this third method is the lower pressure of the binder and thus lower the wear of the device ( particularly the nozzle head ).

After starting the Injektage the lance is pulled gently while turning. The ground is cut open spirally, and wherein there is formed a cylindrical concrete body. By varying the device settings, however, any shapes can be produced.

Depending on the soil conditions and the equipment used column diameter of 3 m and more are possible. DSV Columns can be prepared both vertically inclined or horizontal. By lining up vertical or horizontal windows and walls as well as three-dimensional body can manufacture (for example, tunnel profiles ).

The achievable quality of the concrete body is dependent on the particle size distribution of the soil (depending fine-grained more difficult ). Often the DSV body is roughly equivalent to a concrete of C12/15 quality.

Application

The jet grouting can be used for multiple applications. Basically, the DSV bodies act both static sealing. Some application examples are

• Underpinning of foundations of existing buildings.
• Creating tight pit security constructions.
• The sealing of pit soles.
• Stabilization of problematic soils in tunneling using DSV screen.
• The establishment of sealing shields for dams, etc.

Benefits

One advantage of the jet grouting technique over conventional soil injections is that DSV body can be made to just below the edge of terrain without a rule at prudent approach would heave to worry about. In some applications, an increase in the building by the DSV is also desirable.

In comparison to other methods of securing excavation or underpinning only comparatively small equipment is required for the jet process, which may be optionally employed in the interior of buildings.