Mehrashk Meidani - Dept. of Civil Engineering, School of Engrg., Shiraz Univ., Shiraz, Iran, Lab. of Soil Mechs, Nat. Inst. for Rural Engrg., Kannondai ۲-۱-۶, sukuba, Ibaraki, Japan.
Ali Shafiee - Geotech. Engrg Research Centre, IIEES, No. ۲۸, North Dibaji, West Arghavan, Farmanye, Tehran, Iran
Ghassem Habibagahi - Dept. of Civil Engineering, School of Engrg., Shiraz Univ., Shiraz, Iran
Mohammad K. Jafari - Geotech. Engrg Research Centre, IIEES, No. ۲۸, North Dibaji, West Arghavan, Farmanye, Tehran, Iran

Gravel-Clay mixtures are abundant material in nature and also frequently used in certain civil engineering purposes such as earth dams, levees and landfills. The advantage of using these soils lies in their low permeability owing to clay fraction and high shear strength due the non-cohesive granular part. To date, little research has been done on the performance of these soils and their behavior under cyclic load is still not well known. In order to investigate the cyclic behavior of gravel-clay mixtures, 33 cyclic triaxial tests were performed on 11 different mixtures under various confining pressures, to find the shear modulus variation versus shear strain. Two different types of gravel, i.e. angular and rounded, were utilized to prepare specimens with the same gravel content to investigate the effect of granule shape on the cyclic behavior of the mixture.