Relating shear-induced evolution in topology of pore networks to sand specimen response

Abstract

The shear behaviour of sands is investigated through laboratory testing on reconstituted sand specimens and three-dimensional (3D) digital image-based quantitative characterisation of the topology of pore networks. Specimens prepared using air pluviation and moist tamping methods are subjected to axial compression testing. After shearing, the specimens/microstructures are preserved using a resin impregnation process. Subsequent serial sectioning and image acquisition using bright-field microscopy and image stitching when combined with image montage stacking yield a reconstructed 3D high-fidelity digital microstructure. This paper introduces a computational microstructure tool for analysing geometrical tortuosity of pore structures spatially based on topological skeleton extraction, graph theory and a shortest-path searching algorithm. The tool allows for the tortuous attributes of the highly intricate, heterogeneous pore structure to be evaluated which in turn describes all existing convoluted pathways available for pore-scale transport. Shearing response and strain localisation phenomenon are shown to be influenced by the specimen preparation method as well as the mechanical loading condition. The distribution of pore tortuosity provides new insights into the microstructural evolution induced by shearing which is also closely correlated with the inherent variations in the microstructures.