Experimental investigation of the influence of pyrophyllite on strength, swell, and dynamic behavior of fine-grained soils

In urban planning, it is of great importance that soil analysis for areas selected for construction is carried out using accurate and scientific methods. Since faulty analyses can lead to irreversible damage to structures. Soil consists of different types such as sand, clay, and gravel, each having different engineering properties and behaviors; therefore, suitable designs should be developed by considering the characteristics of the soil in projects. Geotechnical engineering studies soil behavior to ensure the safety and durability of structures and offers various engineering solutions to improve adverse soil properties such as bearing capacity, swelling-shrinkage potential, and moisture sensitivity. Due to increasing urbanization, suitable construction lands are decreasing, and soil improvement methods provide alternatives by making unsuitable soils suitable for construction. Especially in regions with earthquake risk, soil conditions should be carefully evaluated, necessary engineering measures should be taken to ensure structural safety. In this study, pyrophyllite mineral, which is found in reserves in our country and is also used in the cement industry, was used as an additive. The effect of pyrophyllite mineral added in different ratios to two different fine-grained soil samples on the engineering properties of the soil was investigated. Pyrophyllite mineral was added to the soil samples at 0%, 3%, 6%, 9%, and 12% by dry weight. To observe changes in soil properties, standard compaction tests, swelling tests, unconsolidated undrained (UU) triaxial compression tests, and resonant column tests were performed. In the conducted study, pyrophyllite addition in the 6–9% range increased the dynamic strength, reduced the damping ratio, and improved elastic behavior. This effect was observed to vary depending on the soil type, emphasizing the role of mineralogical composition and plasticity characteristics in stabilization. The results showed that pyrophyllite can be used as a sustainable stabilizer in terms of both technical performance and environmental aspects. It offers an effective alternative especially in geotechnical projects exposed to dynamic loading.