Injection grouting

Compacting, waterproofing and stabilising the subsoil

Injection grout bodies are dimensioned in accordance with:

• DIN 4093:2015-11 Dimensioning solidified soil bodies - produced by jet-grouting, deep-mixing or injection methods.
• DIN EN 12715: Execution of works in specialist civil engineering – injection grouting works, and the German version of EN 12715:2000
• General type approvals:
  Z-101.34-35 Silicate gel SIG-60 / Z-101.34-39 Organic soft gel / Z-101.34-43 Silitight 69

The choice of injection technology and injection material depends on the specified purpose of the injection and the mechanical soil properties of the rock or granular soil at hand. However, substances can only be injected into the soil without destroying the soil structure if the grain size of the solid content of the injection material is sufficiently small in relation to the mean pore space of the soil.

It is therefore essential to perform a subsoil investigation tailored to the objectives of the injection work beforehand. A suitable injection agent can be selected based on the fissure width or minimum grain diameter and grain distribution obtained from a sieve analysis and other parameters relating to soil mechanics.

Available injection materials

• Cement/ultra-fine cement as a paste or slurry
  Because of the environmental benefits, we are increasingly using
   (ultra-)fine cements as an ecological alternative to chemical injection.
   
• Chemical injection agents such as silicate gels, soft gels, polyurethane
  The soft gels we have developed ourselves, including an organic soft gel with general type approval, are another economical solution with an excellent carbon footprint.

There are various techniques for producing injection bodies.

Lance injection

Lance injection involves drilling or ramming injection lances into the granular soil or loosened rock. The lances are either placed at different depths or the injection mixture is injected into the subsoil via the opening at the end of the lance when the lance is withdrawn.

The advantages: The process is quick and easy to use, and even small injection projects can be realised economically.

Using injection packers

Injection packers are usually used in stable rock (bedrock). This involves sealing the borehole using single or double packers and injecting the fissures and/or crevices of the exposed borehole wall. We select which height ranges to inject depending on the condition of the rock.

Sleeve pipe injection

From a technical perspective, the best way of stabilising granular soil or unstable or fissured rock by injection grouting is to use the sleeve pipe method. This method involves inserting sleeve pipes into a borehole that has been made in advance. Sleeve pipes have injection openings at regular intervals (approx. every 30cm to 50cm) which are covered with rubber sleeves. After the pipe has been installed, the annular space between the borehole wall and the pipe is encased in a low-strength casing mix. The grout stabilises the borehole and seals off the top of the injection borehole.

After setting, a height-adjustable single or double packer is installed in the sleeve pipe, allowing the corresponding section of the pipe to be pressurised with the injection slurry. When the pressure is sufficient, the valve (cuff) opens, the existing casing mixture is torn open and the injection agent is injected into the substrate at the defined height. The valve action of the injection sleeves allows the substrate to be treated more than once. Different injection agents (e.g. with different rheological properties) can also be injected successively at the same injection point. This method is thus ideal for very high-quality injections in difficult subsoil conditions.