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Underpinnings

Individual solutions.

Different types of underpinnings are necessary if, for example, you want to lay a deeper foundation next to an existing building. In this case, our specialists will install an underpinning body to transfer the foundation loads from the shallow foundations of the existing structure to a deeper foundation level. Underpinning can only be carried out if evidence of the stability of the final state of the planned measure has been provided.

More conventional applications are required when excavation works next to the existing building remove part of the load transfer zone from the existing foundation, which could result in severe subsidence or ground failure. 

Underpinning also includes local relocations of foundation structures in cases where it is necessary to lower or undercut an existing structure.

When reinforcing an existing foundation with underpinning, it is also possible to use this to increase the external load-bearing capacity of the existing foundations or to repair damage caused by unplanned load increases.

Planning expertise for safe and economic implementation

Our skilled engineers are on hand to provide you with comprehensive advice right from the planning stage. We develop the technically and economically optimum solution for your construction scheme on the basis of your specifications.

Individual design

We always carry out underpinning assignments in line with the individual building task at hand.  The choice of method depends to a large extent on the prevailing geological conditions such as stratification of the subsoil or groundwater levels, the existing spatial conditions on site and the planning constraints.

We use the following methods to carry out underpinning work:

  • Jet grouting method (JGM / HPI)
  • Micropiles
  • Conventional underpinning with underpinning walls in accordance with DIN 4123
  • Underpinning with ultra-fine cement grouting

Underpinnings using the jet grouting method

We use jet grouting to securely seal construction pit walls and floor slabs and underpin the foundations of existing buildings. The jet grouting diameters that can be achieved depend on the geological and site-specific boundary conditions. They are calculated individually for each construction scheme.

The difference in height can be securely bridged with jet grouted elements. The underpinning body is usually shaped like a triangle. The individual jet grout sections are constructed using the back-step method in order to avoid overloading the existing foundations and minimise subsidence. When working with greater underpinning heights, additional retaining elements such as grouted anchors or micropiles can increase stability. Jet grout can also be used to stabilise machine foundations that are sensitive to subsidence.

Underpinning with micropiles

Underpinning can also be used when a new underground level is to be built underneath an existing building. Here, the existing foundations must be underpinned in order to avoid subsidence. 

Micropiles are designed to allow several segments to be linked together, means that long piles can be produced – even at low working heights, provided that suitable equipment is used. A wide pool of equipment is available for these applications. At our building yard in Colbitz, the equipment is individually adapted and prepared for the demanding construction tasks.

Underpinning in accordance with DIN 4123

The advance excavation is initially only carried out up to the upper level of the existing foundation. After that, excavation is carried out in sections using the back-step method. Excavation can be as deep as necessary, but no section may be wider than 125cm.

A concrete underpinning wall is constructed immediately afterwards. Only then is the next section cleared. If sections are executed at the same time, a distance of three times the section width must always be maintained between them. After the underpinning has been completed, the construction pit can be excavated to the desired depth. The underpinning should be at least 50cm deeper than the planned new excavation.

Underpinning with ultra-fine cement grouting

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.

The best result for every geotechnical challenge

Benefit from our decades of expertise in specialist civil engineering and problem solving skills – especially when it comes to challenging construction tasks. As a technology leader in specialist civil engineering, we are an experienced advisor able to provide you with expert support, even in the event of unexpected problems, and ensure successful completion of your project.  We have the entire range of specialist foundation engineering methods at our disposal.

Customer benefits

  • In-house technical staff
  • In-house specialist equipment
  • All methods from a single source
  • Quality assurance through individually coordinated
    procedural instructions
  • Metrological testing
     

Selected reference projects

Jet grouting
Central railway station . Frankfurt
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Jet grouting
Pergamon museum . Berlin
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Jet grouting
Office building . Hagnau/Bodensee
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Micropiles
Castle . Lichtenstein/Saxony
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