In nature, soil is commonly found as a mixture of fine-grained and coarse-grained particles, rarely in "pure" fractions. The behavior of soil, including its strength, load-bearing capacity, and stability for future construction, depends on the mixtures of fine and coarse fractions. This study conducted systematic research on a total of 15 experiments: on clean sand without the presence of other particles and sand with varying proportions of kaolin clay. All samples were subjected to small effective stresses of 10, 25 and 50 kPa. The results were presented in diagrams, showing the relationship between shear stress and horizontal displacement, the relationship between vertical and horizontal displacement, the relationship between void ratio and effective vertical stress. For comparison the diagrams are showing the relationship between the angle of friction and cohesion with the percentage of kaolin particles for peak and critical conditions, the relationship between void ratio (according to the normal compression line) with the percentage of kaolin particles, and the relationship between the slope of the compression and critical lines with the percentage of kaolin particles. All test were conducted at the Geotehnical Laboratory of the Faculty of Civil Engineering at the University of Rijeka.