Effects of Gravel Content and Shape on Shear Behaviour of Soil-Rock Mixture: Experiment and DEM Modelling

Abstract The soil-rock mixture (SRM) is an excellent composite filler for subgrade, due to its renewable sources and high structural strength. It is still a challenge to evaluate the impact of gravel content (GC) and gravel shape on the shear behaviour of SRM in pavement engineering, due to the complex and uncontrollable microstructure of SRM. Thus, the aims of the study were: (i) to experimentally analyze the influence of GC and shape distribution of limestone and basalt gravels on shear strength of SRM at various stress conditions; and (ii) to numerically investigate the difference of mesoscale characteristics between SRM models considering irregular shape and proportion by discrete element method (DEM). The test results in the laboratory showed that the Gray correlation of gravel shape on shear strength was greater than that of GC. The numerical results showed that the developed DEM model could accurately predict the mechanical properties and deformation behavior of SRM. As GC increased, the contribution of contact force within gravel particles increased. Meanwhile, the interlocking work had a nonlinear positive correlation with the increase of sphericity. This study implied that morphological characteristics of gravel should be paid more attention to during the design of the SRM subgrade.