Soil-rock mixture (SRM) is a unique type of inhomogeneous geomaterial made up of fine soil and coarse rock gravels. Due to its inhomogeneous composition and distinguishing properties, SRM has drawn great attentions both in theory and in engineering practice. This paper presents an experimental investigation on the internal microscopic processes that soil-rock mixture (SRM) fractures, damages and breaks when subjected to a uniaxial compressive load through the on-site CT scan and the digital image processing techniques. A novel digital image processing algorithm was developed to extract the detailed information of the inside fracture and damage of SRM. Based on the CT identification and the damage mechanics theory, a damage variable was proposed and the isotropic damage property of SRM amid a complete compressive stress-strain response was analyzed. This paper provides direct experimental evidence about the damage mechanism that essentially governs the macroscopic mechanical performance of SRM.
Soil-rock mixture (SRM) is a unique type of inhomogeneous geomaterial made up of fine soil and coarse rock gravels (Liao et al. 2006). Due to its inhomogeneous composition and distinct properties, SRM has drawn great attentions both in theory and in engineering practice. For instance, to just mention a few, Xu & Hu (2008), Li et al. (2004, 2007) and Dong & Chai (2007) studied the relationships between the strength and deformation of SRM and loads, the dimension effects, the relative concentrations of embedded rock and soil, the fractality of shear surface and the influence factors on the properties through laboratory and in-situ tests. The composition factors such as water ratio, maximum grain size, and lithological characteristics were also related to study the variety tendency of intensity index of SRM (Dong 2007). The residual deformation of rock-fill materials and sandy gravels under cyclic loading was tested, and different factors that influenced the residual deformation, such as compaction, saturation and drainage degree, were analyzed (Wang et al. 2000). Based on the laboratory tests, Zhang & Zhang (2004) revised the Young's modulus of Duncan-Chang model. Nevertheless, few studies of knowledge about the mechanical damage property and its internal governing mechanisms are available, which is a serious constraint to properly solving engineering problems.