Heterogeneity induced strain localization in block-in-matrix-soils subjected to uniaxial loading using real-time CT scanning

Abstract

Block-in-matrix-soils (bimsoils) are geological mixtures that have distinct structures consisting of relatively strong rock blocks and weak matrix soils. It is still a challenge to evaluate the mechanical behaviors of bimsoils because of the heterogeneity, chaotic structure, and lithological variability. As a result, only very limited laboratory studies have been reported on the evolution of their internal deformation. In this study, the deformation evolution of bimsoils under uniaxial loading is investigated using real-time X-ray computed tomography (CT) and image correlation algorithm (with a rock block percentage (RBP) of 40%). Three parameters, i.e. heterogeneity coefficient (K), correlation coefficient (CC), and standard deviation (STD) of displacement fields, are proposed to quantify the heterogeneity of the motion of the rock blocks and the progressive deformation of the bimsoils. Experimental results show that the rock blocks in bimsoils are prone to forming clusters with increasing loading, and the sliding surface goes around only one side of a cluster. Based on the movement of the rock blocks recorded by STD and CC, the progressive deformation of the bimsoils is quantitatively divided into three stages: initialization of the rotation of rock blocks, formation of rock block clusters, and formation of a shear band by rock blocks with significant rotation. Moreover, the experimental results demonstrate that the meso-motion of rock blocks controls the macroscopic mechanical properties of the samples.

Keywords

• Image correlation algorithm
• Damage processing
• Real-time computed tomography (CT) imaging
• Rock block motion
• Uniaxial compression