Introduction: when the house starts to “move.”
Any building is not a static object, but a complex engineering system interacting with the soil, moisture, and loads.
In a private residential house in a cottage settlement in the Republic of Tatarstan, this system failed: the walls began to crack, the floor started to settle, and the geometry of the structures gradually deformed. At first glance, the defects looked like typical consequences of building shrinkage. However, the dynamics of their development indicated a deeper process — a change in the properties of the foundation. The engineers’ task was not just to eliminate the consequences, but to restore the stability of the “building-foundation” system.

Initial data of the object
The object of inspection — a private residential house:

• type of structure: brick house;
• number of floors: 1 floor + attic;
• year of construction: 2019;
• condition: occupied house with completed finishing.

Important: during operation, no reconstruction, additions, or changes in the load scheme were made. This meant that the cause of the deformations was not in the building structure, but in the foundation.

Symptoms of engineering instability
Over the course of a year, characteristic signs of uneven settlement were recorded:
Wall deformations:

• appearance and development of cracks in load-bearing structures;
• increase in crack widths;
• concentration of defects in specific zones.

Floor settlement:

• local decreases in floor level;
• violation of horizontally;
• height differences.

Indirect signs:

• changes in the geometry of openings;
• redistribution of stresses in structures;
• progressive nature of defects.

All signs indicated a systemic foundation problem.

Preliminary analysis showed:
The main cause of deformations — reduced bearing capacity of the soil due to increased moisture and loosening.

Process mechanism:

• increase in soil moisture,
• reduction of density and deformation modulus,
• local foundation settlements,
• uneven load distribution,
• cracks and floor/structure settlement.

Thus, the house was in a zone of "engineering turbulence," where the soil ceased to function as a stable foundation.

Diagnostics: soil investigation as the key to the solution
To confirm the hypothesis, diagnostic soil probing was conducted.

The method allowed to:

• determine the structure of the foundation soils,
• identify zones of loosening,
• assess the level of soil water content,
• determine the depth of problematic layers.

Survey results

1. Loosened soil layers were identified in the influence zone of the foundation and floor slab.
2. Increased soil moisture was recorded.
3. Insufficient bearing capacity of the foundation was confirmed.

Engineering conclusion: without intervention, the deformation process will continue and intensify.

Choice of foundation strengthening technology
The designers faced the task of finding a solution that:

• acts on the soil without dismantling structures;
• provides precise reinforcement of problem zones;
• minimally interferes with house operation;
• delivers predictable results.

The optimal solution was the deep injection technology of geopolymer material.

The essence of the method — introducing a polymer composition into loosened soil zones.
During the injection process, the material:

• fills the soil’s pore space,
• displaces water and air,
• increases the density of the foundation,
• forms zones of local reinforcement.

Engineering effect:

• increase in soil deformation modulus;
• increase in foundation bearing capacity;
• reduction of uneven settlements;
• stabilization of building structures;
• improvement of soil filtration properties.

The work was carried out in several stages:
1) Design of intervention

• determination of injection zones;
• development of borehole scheme;
• calculation of material volumes;
• organization of deformation monitoring.

2) Injection works
Polymer injection was carried out through a system of boreholes in the floor slab and foundation zones.
During the works, the following was performed:

• pressure control,
• structural response monitoring,
• adjustment of intervention parameters.

3) Result
Key effects achieved:

• compaction of loosened soil layers;
• stabilization of the floor slab foundation;
• equalization of load distribution;
• reduction of the risk of further deformations.