Microscopic and macroscopic failure mechanisms in sintered soda-lime glass spheres used as sandstone surrogates

Abstract

Cemented granular materials (CGMs) such as sedimentary rocks, ceramics, and sandstones are central to both natural geologic systems and engineered structures. Despite their importance, the relationship between microscopic and macroscale mechanical behavior in natural CGMs is not yet fully understood. To help bridge this gap, synthetic analogs like sintered soda-lime glass beads offer a platform for systematically tuning micro-structural parameters, including grain size and porosity, allowing for controlled investigations into failure processes. In this work, we examine sintered glass bead assemblies at the scale of both particle and bulk specimens to assess their fracture behavior and their applicability as proxies for natural sandstones. A combination of variable sintering protocols, microscopy, tensile testing of sintered bonds, and unconfined compression testing was employed. Key observations include: (1) inter-particle bonds exhibit the presence of pores reminiscent of those found in natural sedimentary rocks; (2) the strength of individual bonds followed a statistical size effect; (3) compressive strengths of the bulk samples fell within the range reported for sandstones of similar porosities; and (4) the strength-porosity relationship matched predictions from pore-emanated crack models but diverged from Hertzian failure models. These results deepen our understanding of failure in sintered CGMs and highlight their utility for studying deformation mechanisms relevant to natural geologic materials.