In many regions of Belgium and the Netherlands, settlement problems are becoming increasingly common in buildings with shallow foundations. Although traditional solutions are effective, they can be costly and quite invasive in certain circumstances. URETEK is renowned for its many years’ experience with a method involving the injection of expansion resin specifically beneath subsided foundations. This minimally invasive technique not only enables stabilisation but often also allows for partial lifting.
As this method has been less extensively researched than conventional methods, a series of tests was carried out at the Buildwise test site in Limelette. The soil consists of calcareous loam with a clay content of 14 per cent and a cone penetration test (CPT) resistance of between 1.0 and 2.5 MPa. Four isolated foundation slabs (foundation blocks) (base area 0.5 × 0.5 m; embedment depth 0.8 m) were installed. An expansion resin was injected beneath three of the foundations. The fourth foundation block served as a reference without grouting.
The distance between the foundation blocks was at least 3 m to avoid interactions between the grout injections. The tests were carried out in accordance with NBN EN ISO 22477-1 (2019). The load was applied to the centre of each foundation using a hydraulic jack. The applied force was measured by a calibrated dynamometer, whilst four displacement transducers measured the vertical displacement of the foundation block.
The results show that, for example, with a stress of 400 kN/m² (load 100 kN), settlements can be reduced from approximately 20 mm to approximately 5–6 mm. Conversely, this means that with a permissible settlement of, for example, 10 mm, the maximum stress can be increased from approximately 280 kN/m² to approximately 600 kN/m². The load tests demonstrate that the strength of a subsoil with low cone resistance can be significantly increased by means of expansion resin injections.