Impact of water–rock interaction on microstructure damage of carbonate rocks and alteration of its micromechanical properties

The interaction between carbonate rock and groundwater, known as the water–rock interaction, can profoundly alter the mineral composition and microstructure of the carbonate rock. To investigate the effects of water–rock interaction on the microstructures and micromechanical properties of carbonate rocks, we conducted surface morphology analysis and micromechanical tests on a typical carbonate rock widely distributed in subsurface: dolomite. The experiments explored its interaction with water over varying durations. The surface morphology, mineral composition, and microstructure evolution of dolomite were examined using scanning electron microscopy and laser confocal microscopy. Ion concentrations in the soaking solution were analyzed using an inductively coupled plasma optical emission spectrometer. The micromechanical properties of samples with varying soaking times were assessed using indentation experiments. The experimental results demonstrated that pure water affected the surface morphology and microstructure of dolomite. Ion concentration analysis of the soaking solution indicated that the levels of Ca2+ and Mg2+ increased with prolonged soaking time. Meanwhile, the number of microfractures on the dolomite surface grew, with structural damage primarily occurring in the dolomite mineral component. These structures led to a significant reduction in the micromechanical properties of dolomite. Furthermore, in the original rock sample, the heterogeneous distribution of mineral components was a key factor contributing to the two distinct trends observed in the elastic modulus and hardness of dolomite as the load increases. In contrast, in the soaked rock samples, the water–rock interaction-induced damage to the microstructures led to different trends in the average elastic modulus and hardness as the load increases.