Influence of mica plates on cyclic strength of soils of old Gediz River Delta

In this study, the effect of grain shape and fine material content on the cyclic strength properties of sandy soils of Old Gediz River Delta (OGRD) has been experimentally investigated. The test materials were recovered from the sandy soil layers within the liquefaction depth (0 m?20 m) by drilling engineering boreholes in the study area. Sand specimens involving platy mica grains, which were taken from the field, were used in the experimental study. By this way, information on strength and stiffness characteristics of regional sandy soils was acquired with a special emphasis on the influence of mica grains.Monotonic, cyclic triaxial and bender element tests were carried out on reconstituted prepared test specimens containing varying fractions of sand and mica grains. Size effect of platy grains was also examined using manufactured mica grains in the mixtures. Also, Standard Penetration Test (SPT) was conducted in the field to determine effect of mica on SPT blow counts (N). In the study liquefaction resistance, post liquefaction volume change, shear wave velocity, internal friction angles at different densities and packing density (maximum and minimum void ratios) of the sand mica mixtures were determined.In conclusion of the study it was determined that mica grains and non-plastic fine materials could significantly reduce to cyclic resistance ratio (CRR) and internal friction angle of OGRD sands. Mica and non-plastic fine materials increase the post liquefaction volumetric strain. It was revealed that mica grains reduce the N values. A relation between N and CRR was proposed for micaceous OGRD sands.