Visualization and Transparentization of the Structure and Stress Field of Aggregated Geomaterials Through 3D Printing and Photoelastic Techniques

Natural resource reservoirs usually consist of heterogeneous aggregated geomaterials containing a large number of randomly distributed particles with irregular geometry. As a result, the accurate characterization of the stress field, which essentially governs the mechanical behaviour of such geomaterials, through analytical and experimental methods, is considerably difficult. Physical visualization of the stress field is a promising method to quantitatively characterize and reveal the evolution and distribution of stress in aggregated geomaterials subjected to excavation loads. This paper presents a novel integration of X-ray computed tomography (CT) imaging, three-dimensional (3D) printing, and photoelastic testing for the transparentization and visualization of the aggregated structure and stress field of heterogeneous geomaterials. In this study, a glutenite rock sample was analysed by CT to acquire the 3D aggregate structure, following which 3D printing was adopted to produce transparent models with the same aggregate structure as that of the glutenite sample. Uniaxial compression tests incorporated with photoelastic techniques were performed on the transparent models to acquire and visualize the stress distribution of the aggregated models at various loading stages. The effect of randomly distributed aggregates on the stress field characteristics of the models, occurrence of plastic zones, and fracture initiation was analysed. The stress field characteristics of the aggregated models were analysed using the finite element method (FEM). The failure process was simulated using the distinct element method (DEM). Both FEM and DEM results were compared with the experimental observations. The results showed that the proposed method can very well visualize the stress field of aggregated solids during uniaxial loading. The results of the visualization tests were in good agreement with those of the numerical simulations.