Effect of waste textile fiber and cement additives on the engineering properties of the soil in high plasticity clay soils

The rapid increase in the population in the world's major cities has led to an increase in underground and aboveground construction, necessitating more efficient use of limited land resources. When ground conditions are unsuitable for building construction, ground improvement techniques are employed to ensure the safety of the structure. Ground improvement techniques aim to not only enhance soil bearing capacity, mitigate liquefaction hazards, and manage settlements but also to offer sustainable solutions that minimize environmental effects and reduce costs. Technological advancements in ground improvement have moved beyond traditional cement and lime-based methods, enabling the use of various additives in recent industrial developments. In this thesis study, the effect of adding textile waste polyamide fiber to high plasticity clay and clay-sand mixture soils on their engineering properties was investigated. In the first stage of the study, the clay sample obtained from the Pazaryeri region of Bilecik province was determined to be in the high plasticity clay (CH) class in the Unified Soil Classification System (USCS) as a result of the soil classification tests. In the study, 16 different mixture test samples were created by adding cement at the rate of 10% of the total weight and waste textile polyamide fiber at the rates of 0.5%, 1.0% and 1.5%, respectively, to clay and clay-sand mixtures. The mixtures prepared according to the determined mixing ratios were prepared with care to ensure equal mixing and were then compressed with standard proctor energy. After the optimum water content values at which the mixtures reached their maximum dry unit volume weight were determined by the Proctor test, samples were prepared at the optimum water content corresponding to these values and kept for different curing periods (0, 3, 7, 28 and 90 days). At the end of the curing period, free pressure and ultrasonic pulse velocity experiments were performed on the samples and the strength and internal structure changes of the mixtures over time were examined. As a result of the studies, it has been shown that textile waste polyamide fiber positively affects the strength and engineering properties at rates up to 1.0%.