The most popular foundation technique used in the case of weak soils (soft soils) is replacement of subsoil. However due to high costs and time-consuming the replacement method is superseding in favor of strengthening and/or stabilization. Strengthening consists in mixing the subsoil with the additive which has to improve the mechanical parameters of soil. In the stabilization process, heavy equipment is used under which a working platform should be made. These types of platforms are usually made by mixing soil with cement or similar specimen. Unfortunately, cement is very expensive material - 600 PLN/ton. For this reason, cheaper but equally effective alternatives are often sought. One of them is fly ash, which is widely used in many branches of civil engineering, for example flood protection in dikes or concrete component. The aim of this project is to investigate the effect of the fly ash on organic soils. The experimental investigation will consist a series silt-fly ash mixture in various proportions. The next step will be to conduct tests in an oedometer and shear box, in which the compressibility modules and shear strength without drainage will be determined. The final stage of the research will be to compare and analyze the values of the obtained parameters for pure organic soil and other mixtures (the detailed table is included in the application). The Department of Geotechnical and Hydraulic Engineering is equipped with necessary equipment enabling the performance of the tests described above. Unfortunately, the ash used to strengthen the organic soil has an alkaline reaction, which in the case of longer contact (one oedometer test is about two weeks) with the chamber of oedometer made of aluminum causes its corrosion. A similar situation also applies to a box chamber in a direct shear box apparatus. It is estimated that after testing the compressibility modulus for pure fly ash, both chambers (we have two oedometers in the Department and tests are planned to be performed in parallel) will not be suitable for further use. Therefore, in order to complete the research plan described above, it is necessary to purchase min. 4 chambers to each apparatus. Funding obtained under this grant will allow the purchase of the above mentioned spare parts of equipment and carrying out all tests without the need to stop work in the event of damage to any of the chambers during the test.