Vahid Yazdanjou - Graduate student School of Engineering, Tarbiat Moallem University
Seyed Nima Salimi Eshkevari - Graduate student School of Engineering, Tarbiat Moallem University
Amir Hamidi - Assistant professor School of Engineering, Tarbiat Moallem University

Most of the previous constitutive models used for investigation of the shear behavior of sandy soils have been developed without consideration of the oversize particles. The size of experimental samples is an important limitation in this case. In this research a laboratory study has been planned to investigate the shear strength of sandy soils containing different gravel contents. The tests conducted using a large scale direct shear apparatus with a 300mm×300mm shear box. All the tests have been performed on dry samples in drained condition. The gravel contents of 20, 40 and 60 percent were used in sample preparation. The tests conducted in three different densities of 35, 60 and 85 percent and three different surcharges of 1.5, 3 and 4.5 kg/cm2. It was observed that the increase in gravel content and relative density results to an increase in the shear strength and dilation of the mixture. The gravel particles are floating in sandy soil matrix in lower gravel contents. As a result the shear behavior is mainly controlled by the sandy matrix behavior. However, as the gravel content increases in sandy soil, the non floated state of the gravel controls the behavior of sand-gravel mixture.

Shear strength, sandy soil, density, Gravel content, surcharge.