Large scale direct shear tests on remolded colluvial mixture samples were carried out in laboratory on the basis of gradation analysis. The deformation and strength characteristics of colluvial mixture with different rock particle contents were studied combined with simulation by two dimensional particle flow code PFC2D. By synthesizing the numerical and testing results

it is concluded that the colluvial mixture with higer content of rock particle behaves strain hardening. Colluvial mixture samples exhibit shear dilatation characteristics at low normal stress level

and tend to have shear contraction at higher stress level. If the rock particle content is less than 40%

the mechanical characteristic of colluvial mixture is controlled by soil; while this content is greater than 80%

its mechanical characteristic is influenced by rock alone.