Marls are one of the problematic soils that undergo more erosion due to their deformability and sensitivity to humidity and weather conditions. The effects of these soils have been observed on subgrades of pavements, abutment of dams, foundation of high-rise structures, the interaction of soil-structure and etc. The strength and deformation of marls are more effective to moisture content. In addition, the dynamic parameters of theses soil are considerable as well as static geotechnical specifications. Soil dynamic parameters can be obtained from both laboratory experiments and field experiments. With the aim of understanding the dynamic behavior of marl soils, this study was carried out to evaluate the marls of northwest region of Shiraz City which is mixture of marls containing the expansive anhydride gypsum. For this purpose, the laboratory cyclic triaxial test and in situ downhole test has been performed. The results showed that for normal consolidated marls, with increasing the confined pressure from 400 to 600 kPa (increasing soil depth), the shear modulus increases from 50 to 200 kPa. In addition, the behavior of the damping ratio is relatively different for strains less than and greater than 1%, but in general, for strains higher than 1%, the damping ratio decreases from 0.21 to 0.18 with the increase confined pressure from 100 to 600 kPa.
