Shear fracture behavior in dolomite: The interplay of thermal cycles and confining pressure

Abstract

Understanding the influence of temperature fluctuations and confining pressure on shear fracture behavior is essential for predicting the stability of rock formations in geomechanical and geological engineering. This study investigates the impact of thermal cycling (0, 50, 100, and 500 cycles between 20–60 ℃) and confining pressure (0, 3, 6, 12, 24, and 48 MPa) on shear fractures induced in dolomite under pure mode II conditions, utilizing the Short Core in Compression (SCC) method on 72 samples. Microstructural evolution and phase transitions were assessed using Scanning Electron Microscopy (SEM) and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) before and after thermal cycling. The evolution of dolomite's microstructure closely correlated with the results of mechanical tests. The microstructure improved with thermal cycling up to 352 cycles due to the expansion of dolomite grains and a reduction in the void and crack volume. Beyond this threshold, the microstructure deteriorated as void volume and crack expansion increased. Consequently, the fracture toughness and shear modulus of shear fractures induced in SCC specimens increased by 32–111 % and 38–54 %, respectively, under varying confining pressures with increasing cycles up to the 309–379 cycle threshold, after which they decreased. Thermal cycling and lateral pressure have a direct influence on shear fracture morphology. Roughness increased by 16–99 % under varying confining pressures with increasing thermal cycles up to the threshold, as mentioned earlier, which explains the enhanced mechanical properties of these fractures due to increased friction. This study advances our understanding of how thermal cycles and confining pressures affect shear fracture behavior, which is critical for the safety and stability of geological structures exposed to these conditions, such as rock slopes, landslides, and deep geothermal engineering projects.

Keywords Confining pressure, Dolomite, Shear fractures, Shear modulus, Short Core in Compression (SCC), Thermal cycles