Stress-strain relationship of soil-rock mixture based on homogenization theory

Soil-Rock Mixture (SRM) is a kind of discontinuous and heterogeneous geotechnical material, and its mechanical property has become a subject of debate in geotechnical engineering. In the present study, SRM was assumed to be an ideal binary medium material, in which the rock and soil were assumed to be brittle-elastic and elastic-plastic media respectively. Duncan-Chang model was employed to define the constitutive relationship of soils. A new parameter named local strain coefficient of rock was adopted to relate the microscopic strain of the media and the volume average strain of SRM. The stress-strain relationship of SRM was then obtained by the simple homogenization theory. A series of tri-axial tests were conducted for the residual soil from Guangdong Province to obtain the coefficients in stress-strain function. The final relation curve could reflect the stress-strain relationship of SRM preferably under different conditions. The results show that the shear strength of SRM increases relatively with the increasing of confining pressure and volume rock rate of SRM. However, the strengthening effect by rock is not obvious when the volume rock rate is less than 0.3.