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Injection grouting

in accordance with DIN EN 12715

Stump-Franki has consistently promoted the development of injection grouting technology, particularly with regard to (ultra-fine) cement technology and has also carried out important research work in this field. We have many years of experience thanks to a multitude of successfully completed projects. This makes us your ideal partner with comprehensive expertise in every aspect of injection technology.

Quality documentation

We rely on mixing plants and injection containers with sophisticated technology for our injection work. All the key manufacturing parameters are recorded and then digitally evaluated. This enables us to guarantee safe implementation at a consistently high level.

Environmentally friendly and safe

Sustainability is a key priority for us when it comes to carrying out injection work and injecting grout into the subsoil. For this reason, we have developed an organic injection agent for which we have obtained a general type approval (formerly referred to as building authority approval) from the German Institute for Building Technology (Deutsches Institut für Bautechnik, DIBt). Sustainability aspects are reviewed in detail before every construction project begins.

Technology brochure
Injection grouting (only available in German)
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Applications

Injection grouting technology is used in granular soil and rock to stabilise and seal the subsoil.

Applications include:

  • Sealing slabs in construction pits
  • Underpinning buildings and other structures
  • Subsoil sealing / grout curtains
  • Controlled elevation
  • Backfilling cavities
  • Pipe shield covers
  • Soil stabilisation
  • Masonry rehabilitation
     

Advantages

  • Stabilisation and sealing of the subsoil
  • Flexible adaptation to new findings relating to the subsoil, unforeseen obstacles, or changes in planning.
  • Can be implemented in confined spaces or restricted working heights when small devices are used.
  • Injection technology causes very little settlement and offers the possibility of selectively elevating the existing buildings as desired.
  • The production of injection grouts is low-noise and vibration-free, making this method particularly suitable for use in densely populated areas and in the vicinity of neighbouring buildings that are sensitive to vibrations.
  • Very low carbon footprint due to minimal use of cement and significantly less transport.
  • Environmentally friendly process with soft gels made from ingredients that do not pollute groundwater.
  • Soil contamination is low when using our proprietary organic soft gel. This is a tried and tested procedure: We have three separate general type approvals from the DIBt for soft gels.
  • Safety during execution is monitored by high quality assurance standards.


The wide range of available design variants allows us to offer the very best solutions for every construction site and every subsoil.

Basic facts

Standards and regulations

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


Injection materials

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.

 

Injection procedure

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.

Quality assurance

We establish an individual quality assurance programme for each injection project. This defines tests in all execution phases, in accordance with the requirements of DIN EN 12715. The specific procedure and the scope of the tests must be determined and put out to tender in advance for each construction project. As experts, we will be happy to advise you on this.

Continuous slurry monitoring

Consistent quality of the injection agent is essential for a successful injection process. For this reason, the rheological properties of the injection agent, in particular the density and flow properties, are monitored and documented daily with on-site testing. Our specialist teams are trained in monitoring procedures; they identify changes at an early stage and ensure safety throughout.

Digital injection monitoring for safe workflows

Essential parameters such as flow rate and injection pressure are continuously recorded digitally for each injection borehole during the injection process and fed into the computerised evaluation. This approach ensures that our work processes remain safe at all times.

Thorough analysis

The results of the injection protocols are pooled and evaluated in order to verify the success of the injections. Core drillings are also used to check the stabilising bodies. Depending on the subsoil, additional borehole tests are carried out to determine the permeability.

We ensure high execution quality with:

  • Individually coordinated instructions
  • Our own DIBt general type approval for soft gels
  • Compliance with the requirements of execution standard
    DIN EN 12715
  • Constant monitoring of the injection agent
  • Digital monitoring and evaluation of the manufacturing parameters

Clear processes governed by our quality management system in accordance with DIN EN 9001:2015

Design variants

Sealing slabs with soft gel injection grouting

Economical and environmentally sound

Sealing slabs are used to seal the surface of construction pit bases against groundwater rising from below. Stump-Franki Spezialtiefbau produces very economical, safe soft gel injection slabs with an excellent carbon footprint as an alternative to the jet grouting method. Stump-Franki has obtained three general type certifications from the DiBt for its soft gels:

  • Stump organic soft gel
  • Stump silicate gel SIG-60
  • Stump Silitight 69


The injection boreholes for inserting the injection pipes are drilled by means of flush drilling or pile driving across the entire floor of the construction pit, and are at a fixed distance from each other. The soft gel is injected into the pore spaces of the subsoil in the injection horizon through the injection lances/valves installed in the boreholes. The soft gel is injected in the same way as the conventional penetration injection: pump pressures or pump rates are set so that the stable injection mixture can penetrate into the pore spaces of the soil and thus reduce its permeability.

Underpinnings / pore injection with sleeve pipes

If the soil conditions are suitable, pore injection can be used to form structurally effective underpinning bodies in addition to waterproofing bodies. Our experts have extensive experience and expertise in performing this demanding injection work.

Subsoil sealing / fissure injection

Secure seals in any environment

The choice of binder and rheological properties depends on the size of the fissures. As a rule, when working in stable rock, the injection borehole is first drilled to its final depth and then grouted section by section. The length of the grouting sections is selected according to the distances between the fissures.

Rock injection grouting is often used to seal the subsoil under a dam. We have a broad range of technical capabilities, which allows us to adapt our equipment systems to enable us to drill long holes with directional accuracy, even in confined spaces.

Elevation injection grouting

Controlled elevation for high safety

Tunnel construction projects or changes in the groundwater level can cause structural subsidence. The resulting misalignments can be corrected with elevation injections. Our extensive measurement systems allow us to guarantee a high level of safety during execution.

Masonry injections

Preservation of historic buildings

In addition to subsoil injections, this technique is also used to rehabilitate old buildings. Combining specialist foundation engineering and the preservation of foundations and masonry in listed buildings is one of our core competencies.

Backfilling cavities

Secured for the long term

Cavity backfilling involves drilling into selected cavities and backfilling them with a suitable injection agent. This method is especially widespread in regions with abandoned mines.

Using modern processing and conveying technology, we are able to permanently secure large cavities by selectively filling them with defined materials.

Compaction grouting

Displacement and compaction

Displacement injections, also known as compaction grouting, are carried out in the same way as lance injections. Mortars and thick slurries are used as grout. Injecting the grout displaces the surrounding soil and compacts it. The injection volume can be flexibly adjusted depending on the soil layer. This allows for the compaction of individual layers as well as the creation of continuous columns that act as load-bearing elements.

Selected reference projects

Injection grouting
New waterworks Dörenthe . Ibbenbüren
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Injection grouting
Quartier Hoch 4 . Mannheim
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Injection grouting
Stabilisation of a historic city wall . Aachen
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