Theoretical Analysis and Experimental Research on Multiscale Mechanical Properties of Soil

The skeleton of soil, which consists of soil particles at various scales, is a complex granular material and displays multiscale and hierarchical mechanical properties. The coupling effects of deformations at different scale levels of the soil structures have great influence on the macroscale mechanical behaviors of the soil. According to the scale divisions of soil and the physical and mechanical effects generated by the interactions between soil particles at different scales, a soil cell element that can describe the internal material information and particle characteristics of soil was constructed. On the basis of this soil cell element, a soil cell element model that can characterize the multiscale mechanical properties of soil is proposed. A series of unconsolidated and undrained triaxial compression tests on saturated, remolded soil samples with a variety of particle combinations was designed to analyze the proposed soil cell element model. The results show that the macrostrength of soil increased with an increase in the density of coordinated microcracks and effective strain gradient. The relationship between the macrostrength of soil and each of these two parameters can be presented as a parabolic function, respectively. The soil cell element model, which establishes the relationship between macrostrength and the intrinsic length scale and the effective strain gradient, can reproduce and predict the multiscale mechanical properties of soil. In the soil cell element model, the intrinsic length scale is a reflection of the geometrical morphology of microcracks, and the effective strain gradient is a reflection of the shape distortion of the mesoscale soil cell element. The experimental data can be well fitted to the soil cell element model. These research results are significant for the development of a multiscale theoretical framework that links different coupling scales.