Effect of meso-mechanical variables on the deformation properties of the multi-phase geomaterial

Abstract

Multi-phase geomaterials can be classified as the particulate composites composed of finer matrix and dispersed coarser inclusions, and their mechanical properties are controlled by the meso-mechanical variables. Classical mechanical models assume the inclusion’s size-independent meso-variables to predict the overall elasticity of composites, which has been doubted in recent analytical/numerical modellings and experimental observations. Considering the equivalent homogenization for composites based on the averaged meso-stress distribution, the discrete element method has been used to conduct a series of confined compression tests on the composite specimens with constituents of cohesionless granular matrix and bonded inclusions. Results from the tests of composites with monodisperse/polydisperse inclusions show that the inclusion’s size induce little effect on the average stress in the phase of matrix and inclusions and the overall elasticity, if the mechanical contrast of inclusion to matrix and the inclusion proportion are constant. The interphase effect on the mechanical properties of composite has also been discussed through the stress transfer characteristic and the internal contact force distribution. It is further verified that Chamis model can give the satisfactory prediction of stress field and overall deformation characteristic of the composites with different inclusion proportions (10%, 20%, 30%, 40%). Moreover, the damage characteristic and stress path of inclusion have been explored, indicating that the damage degree of inclusion is positively related to its effective shear stress, which gives the damage criterion of inclusion in the composites under confined compression.