The effect of micro-scale grain orientation on macro-scale soil behavior

The change of physical and mechanical behavior of soils according to direction is defined as anisotropy. During the formation of soil layers, the orientation of the grains tends to minimize their energy. Vertical and horizontal compressions in soils may have difference due to overburden and horizontal pressures. In addition to these factors, the properties of soils such as compression properties, strength and permeability may have differences depending on the direction, with the effect of many factors. ‎ In this study, the effect of grain shape and size on the strength and compression properties of sandy soils was investigated with an experimental study program. ‎Within the scope of the study, the ‎Old Gediz River Delta sandy soils which are known as in naturally contain abundant platy grains by weight were used.‎ The effects of platy grains on the behavior of sandy soils has been investigated from two aspects. (1) The effect of size ratio of the mica grain (Lmica) to the sand grain size (Dsand) on the behavior, (2) the effect of the platy grains on the anisotropic properties of sandy soils. ‎ For this purpose, sand-mica mixtures in different Lmica/Dsand sizes and different mica contained specimens were prepared. In order to determine the effects of mica grains on anisotropic behavior, test specimens were prepared by air-pluviation method in shear box cells at different angles to the horizontal. ‎ Then, the shear box cell was placed to the original horizontal position and the shear box tests were carried out. At the end of the study, it was observed that the size ratio of the platy grains has a significant effect on the strength and compression properties. Similarly, it has been determined that there are significant differences between the anisotropic properties of sandy soils contain mica grains and without platy mica grains.