关键词: 粉砂岩, 白云石, 力学性能, 损伤, 能量, CT扫描

Abstract: Dolomite is formed via dolomitization, a process that enhances porosity. Investigating the influence of dolomite as a characteristic mineral on the deterioration of the physical and mechanical properties of siltstone is significant for the design and stability prediction of deep underground engineering. This study employs X-ray fluorescence spectrometer (XRF), X-ray diffraction (XRD), microscopic analysis, ultrasonic wave velocity measurements, and nuclear magnetic resonance testing to quantify dolomite’s impact on siltstone’s physical parameters. Brazilian splitting tests, monotonic loading, and cyclic loading-unloading experiments reveal the evolution of mechanical parameters, including tensile and compressive strengths. An apparent elastic-viscous-plastic damage model is developed, and dolomite-induced deterioration mechanisms are investigated using computed tomography (CT) and scanning electron microscopy (SEM). The results indicate that: 1) Dolomite content enhances particle roundness, weakens intergranular interlocking, and creates distinct boundary pores with calcite, leading to enhanced pore connectivity and a 2.77-fold increase in porosity. 2) Dolomite presence reduces maximum tensile strain, decreases compressive strength by 14.5%, extends the compaction phase by 9%, and shortens the stable crack propagation phase by 12%. 3) A larger cyclic loading-unloading difference correlates with higher damage values. Dolomite-free rocks exhibit significant damage variation, with rapid early-stage increases followed by slower growth, whereas dolomite-containing rocks show more stable damage progression, with dolomite inducing more pronounced elastic-viscous-plastic damage accumulation. 4) Cracks in dolomite-free samples are bent, dissipating more energy with lower energy storage values, while those in dolomite-containing samples are straight, dissipating less energy with higher energy storage values. Dolomite enhances porosity, facilitating crack propagation and increasing the proportion of tensile cracks.

Key words: siltstone, dolomite, mechanical properties, damage, energy, CT scan