Dynamic three-dimensional imaging and digital volume correlation analysis to quantify shear bands in grus

Abstract

The meso-deformation evolution in grus is crucial to the mechanical characteristics. Although the macroscopic deformation of grus has been widely studied, its physical meso-scale deformation and shear band evolution have not been well understood. In this paper, high energy X-ray computed tomography (CT) measurements and digital volume correlation (DVC) were performed on a grus sample under triaxial compression in order to quantify shear strain and shear bands in grus. Besides, a series of three-dimensional octahedral shear strain was obtained by DVC analysis. Furthermore, the corresponding evolution of the shear band, content, distribution characteristics and connectivity were investigated. The results show that the shear bands are formed at the stage where the axial strain is equal to 8%; generally, they are obliquely distributed as a whole and connected in an irregular flat strip shape; besides, the failure path may cause the grains to divert or branch due to the anisotropic distribution of grains. Moreover, the octahedral shear strain approximation obeys the χ2 distribution. There are at least two types of distribution of shear bands. Small-scale shear bands may be generated in different areas in the material at the initiation state, whereas the correlation and directionality between the variety of shear bands are slight; while at the shear failure stage and the subsequent stages, a close correlation is found between the shear bands, the direction consistency is significant.