Sustainable solutions for unstable soils and settling structures

May 22, 2024

Unstable foundation subsoil continues to pose major challenges to designers and engineers in the construction industry. It gives rise to unstable and cracked structures exceeding ultimate and serviceability limit states. In order to provide effective and long-lasting solutions in these cases, MC-Bauchemie has developed the MC-Montan Injekt product family, a range of special geotechnical injections for soil and ground stabilisation, as well as for lifting concrete slabs and structures.

Soil stabilisation methods aim to improve the load-bearing capacity and resistance to deformation of a substrate in order to make it permanently resistant to mechanical loads.
Soil stabilisation methods aim to improve the load-bearing capacity and resistance to deformation of a substrate in order to make it permanently resistant to mechanical loads.
© MC-Bauchemie 2024

Soil stabilisation methods aim to improve the load-bearing capacity and resistance to deformation of a substrate in order to make it permanently resistant to mechanical loads. At the same time, the susceptibility to the effects of water and frost can be reduced. However, the focus is on preventing potential subsidence of structures, which is often caused by shear failure and soil compaction, but may also be due to water washout and associated soil erosion and suffusion (displacement and removal of fine soil particles in the soil) caused by leaching and the presence of water.


These processes can lead to cavities or depressions in soft soil layers or loose rock and ultimately to settlement or deformation of the structures above them. Soil stabilisation and the raising of the structure provide a remedy here.

Innovative resin-based subsoil injections

In order to specifically stabilise and consolidate soft layers, special grouts are injected into the subsoil; these injection compounds are generally based on polyurethane and organo-mineral resins and are characterised by very good penetration, optimal expansion force, high strength and fast curing. The injection resins in the MC-Montan Injekt product family help to compensate for difficult ground conditions and reinforce the subsoil so that it can bear more load and also enable structures to be lifted.


Another advantage of MC’s innovative injection solutions lies in their rapid effectiveness. Ideally, a repair or reinforcement of the substrate can even be carried out within just one hour and, under certain circumstances, during ongoing operations. This is of crucial importance because factory or even residential and office buildings that have settled due to effective vertical stress would have to be closed for a longer period of time if they were to be repaired with conventional methods.

Compaction through displacement injection

There are different technical application methods for grouting soils. Displacement injection involves the targeted displacement and compaction of soil particles. It is suitable for almost all types of soil, regardless of whether clay, silt or sand. With displacement injection, special resins are injected into the foundation subsoil at the exact location and depth required, using injection lances and pumps. The resin expands primarily in a lateral direction and displaces the soil, causing it to compact. This leads to improved shear strength, a higher modulus of elasticity, increased cohesion and higher shear angles. The soil’s load-bearing capacity is thus increased, while its deformability is reduced.

Penetration grouting of loose rock particulate

In the case of penetration without displacement, high-performance grout is injected at low pressure into the space between the soil particles. There it forms a solid rock-resin matrix with high strength, low deformation properties and improved elasticity. This process is ideal for fine-grained loose rock such as sand.


With the MC-Montan Injekt product family, MC offers for these applications innovative injection solutions that are precisely aligned to the respective technical requirements and have proven their efficiency and effectiveness in numerous projects worldwide.

MC-Montan Injekt L series – the standard-setter

The four products in the MC-Montan Injekt L series belong to the displacement injection category. They are: MC-Montan Injekt LE, LE-S, LE-S 60 and LE-S 100. The ‘LE’ stands for ‘Lifting Expansion’. These products cover a wide range of technical properties and set new standards in soil compaction. MC has developed design criteria for optimising consumption and the required injection depth, all of which meet the requirements specified in the relevant Eurocodes.


While MC-Montan Injekt LE-S 100 meets the requirements for high load-bearing capacity,
MC-Montan Injekt LE-S covers the requirements for grouting in deeper layers with high expansion force. MC-Montan Injekt LE-S 60 offers a perfect average value with sufficient strength and expansion properties, making it suitable for most common applications. In addition to stabilisation and consolidation, application of these resins has positive effects on both erosion control and water permeability control. In particular, the controlled expansion force applied during deep injection of the resins enables minimally invasive, controlled lifting of components and structures. Such an application can be carried out quickly and precisely using portable, lightweight equipment. Products from the MC-Montan Injekt L range are used for work on foundations, carriageways, floor slabs, runways, railways, for cavity filling and for shoring of wall and rock crevices.

MC-Montan Injekt F series for strong hold

The low-viscosity MC-Montan Injekt F series of resins, where F stands for ‘force’. and injection takes place without soil displacement, are used to seal and consolidate structures and rock.
There are also four products in this range: MC-Montan Injekt FR, FN, FS and FF. These high-strength resins are categorised according to their reactivity and foaming potential.


While MC-Montan Injekt FR reacts within a few seconds, FS reacts after 30 minutes. MC-Montan Injekt FN comes with a reactivity of 1 minute, the most frequently adopted reaction time. MC-Montan Injekt FF generates a controlled, load-bearing rigid foam that is used for cavity filling where optimised strength is required.


With the MC-Montan Injekt F series, you can perform underpinning without excavation, while also controlling water permeability. The range of applications for MC-Montan Injekt products for penetration grouting extends from foundations and floor slabs to roadways and runways, and on to anchoring and shoring walls for the temporary stabilisation of excavations. MC-Montan Injekt F series products can also be used for micro and mini pile applications by tube-a-manchette grouting and conventional perforated lance injection methods.

Successful application in Dubai

A project in Dubai shows just how reliable and efficient the solutions provided by MC-Montan Injekt products are. About five years after its construction, a water treatment plant there began to show signs of subsidence. The reason: The penetration of water into the soil caused the dissolution of lime deposits, leading to void creation. In addition, five columns had tilted by up to 3° under their own weight of 135 tonnes. These have been uprighted again with a tolerance of 1 degree.


The clients and planners played through various scenarios. Compared to the solution of fracture-grouting the substructure by directional drilling from outside, followed by micropiling and cement-grouting, the option proposed by MC involving displacement grouting under the affected foundations, slabs and tension members with MC-Montan Injekt LE-S proved to be clearly superior. As the affected area contained high-tech equipment, removal and reinstallation of those assets would not only have been costly, but the downtime required for the retrofit would have caused significant disruption to the client.


With the use of MC-Montan Injekt LE-S, on the other hand, a precise and customised approach could be guaranteed. To this end, MC also trained the applicators and enabled them to carry out the demanding work precisely as required, so that the client was able to continue operating its facility with only minimal restrictions during the repair. This helped the client retain its market position and also saved considerable direct costs.

MC-Montan Injekt for new and existing buildings

Foundation subsoil compaction is always necessary on construction sites; in new construction, for example, to protect excavation pits from water ingress and subsidence, to ensure the load-bearing capacity of the subsoil for structures or to allow access for heavy equipment. However, existing structures can also settle due to construction defects, flooding, landslides, loss of stability, burst pipes or normal erosive phenomena, making it necessary to compact the subsoil and raise the structure.


In these cases, the special resins of the MC-Montan Injekt product family, which meet the high-spec of the relevant Eurocodes, can be used for a wide range of geotechnical injections for a precise, versatile, cost-effective and time-saving solution.


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