Effects of rock block content and confining pressure on dynamic characteristics of soil-rock mixtures

Soil-rock mixture (S-RM) is a complex geo-material characterized by competent rock inclusions floating in a weaker soil matrix structure. The mechanical performances of it are significantly controlled by the interaction and properties of rock blocks and the external environment. In this study, experiments on S-RM were conducted through a large-scale triaxial apparatus for investigating the effects of rock block content and confining pressure on the dynamic characteristics of them. The features of the axial stress and strain time-histories of S-RM were analyzed. The reductions of the maximum shear modulus and the dynamic shear modulus ratio were investigated. The increase in the damping ratio was explored. And the effects of rock block content and confining pressure on the dynamic characteristics of S-RM were discussed in detail. Results indicate that there is an approximately linear relationship between the maximum shear modulus and the rock block content while an approximately exponential relationship between the maximum shear modulus and the confining pressure. The distribution of the dynamic shear modulus ratio of S-RM takes on a low dispersion at the same normalized shear strain. The unnormalized/normalized damping ratio of S-RM is increasing with the shear strain and takes on a feature of zonal distribution as a whole. Both the dynamic shear modulus ratio and the normalized damping ratio of S-RM could be evaluated by a function of normalized shear strain. The four-parameter formulas for the dynamic characteristics of S-RM were introduced for all practical purposes in the final. The results of this study can provide a reference to further understand the dynamics performance and the parameter determination of S-RM and other similar geo-materials.