Abstract: To investigate the soil grain size as well as the sample size effect on the stressstrain characteristics of the granitic residual soils, consolidated undrained triaxial shear tests were performed on remolded granitic residual soils with grain sized greater than 5mm removed under three different sample diameters for the triaxial shear tests. The results indicate that the stressstrain curves from samples tested under different diameters are similar with different stress magnitudes; the presence of the large grain size in the sample will increase the tested effective cohesion and reduce the internal friction angle. When the large grain soils are removed from the samples, with the increase of the sample diameters, the tested effective cohesion increases and the effective internal friction angle reduces. However, the total cohesion reduces and total internal friction angle increases with the sample diameters. In general, the sample size has a larger impact on the effective cohesion and less impact on the effective internal friction angle.

Key words: Granitic Residual Soils, Size Effect, Triaxial Tests, Shear Strength, StressStrain Characteristics