(1. School of Civil Engineering and Transportation，South China University of Technology，Guangzhou，Guangdong 510641，China；2. State Key Laboratory of Subtropical Building Science，South China University of Technology，Guangzhou，Guangdong 510641，China)
Abstract：According to the size and connecting characters of soil particles，soil is discomposed into two components as matrix and reinforcement particles respectively with a certain size demarcation to investigate the influence of the microstructures on soil strength. Based on the strain gradient theory and the notion of coordinated microcracks required for the compatible deformation between the matrix and the reinforcement particles，a multi-scale “matrix-reinforcement particle” model is established to study the size effect of soil strength which indicates that the soil strength is related to the intrinsic length scale，the strain gradient，the properties of the matrix as well as the size and gradation of the reinforcement particles. A series of consolidated and undrained triaxial compression tests on unsaturated remoulded soil were designed to study the size effect of soil strength and to determine the intrinsic length scale quantitatively. The results show that：the yield stress of soil increases with the decrease in the reinforcement particle size and has a linear relation on the reinforcement particle content；moreover，the relationship between the yield stress and the intrinsic length scale could be presented as parabolic function；the intrinsic length scale increases with the increase in the matrix liquidity index，the particle size and particle content of the reinforcement particles；and the relationship between the intrinsic length scale and the reinforcement particle content can be presented as parabolic function. The experimental data can be well fitted to the “matrix-reinforcement particle” model. The research results are significant to the development of strength theory of soil.
2013, Vol. 32 
