Investigation of the geotechnical properties of sand-amended clay soils

The soils encountered at construction sites do not always possess the desired properties. There are various methods for improving the geotechnical properties of soils, one of which is the use of additive materials. Clayey soils generally exhibit low strength and materials such as lime, asphalt, sand, and cement can be used to improve their geotechnical characteristics such as swelling, permeability, and strength. In this thesis, the changes in the geotechnical properties of a clayey soil were investigated by adding fine sand and cement. Mixtures of clay, sand, and cement were prepared by adding fine sand at rates of 5%, 10%, 15%, and 20% by weight, and cement at rates of 1% and 3%. The prepared specimens were subjected to liquid limit, plastic limit, standard Proctor, consolidation, permeability, and unconfined compressive strength tests. As a result of the experiments, the plasticity indices and soil classifications of the samples, dry unit weights, optimum water contents, swelling percentages, permeability coefficients, and unconfined compressive strengths were determined. The soil classification of the mixtures was identified as CL. According to the Proctor analyses conducted on the mixtures, an increase in sand content led to a decrease in water content, while the addition of sand and cement increased the dry unit weight values. It was also observed that the dry unit weight values of the mixtures were higher compared to the clayey soil alone. The water content measured in the clayey soil was found to be lower than that of the mixtures, and it was noted that as the sand and cement contents increased, the water content decreased. In the mixture soils, as the proportions of sand and cement increased, the swelling pressure values decreased, showing a reduction compared to the pure clay as well. It was observed that increasing the proportion of sand and cement in the mixtures relative to the clay increased the strength of the soil. According to the results of the permeability test, an increase in sand content led to an increase in permeability, whereas an increase in cement content caused a decrease. The results suggest that the engineering properties of soils can be improved with the addition of sand and cement, and that this method may be a suitable ground improvement technique for soils with low strength and high swelling potential.