Mechanical behavior and macro-meso damage evolution of sandstone under long-term water immersion

Abstract

Mechanical behavior degradation of sandstone due to long-term water immersion is critical when assessing the stability of rock masses in geothermal recovery systems from abandoned/closed mines. In this study, a macro/meso-scale experimental framework was employed to investigate the influence of water immersion on sandstone. The sandstone samples were subjected to uniaxial compression after being immersed in water for various days (0–150 days). X-ray computed tomography (CT) was employed to reveal structural evolution and mechanical degradation under water – rock interaction. The results show that the peak strength and elastic modulus decreased by 64% and 67%, respectively. CT analysis revealed a transition from isolated mesoscopic pores to interconnected macroscopic pores, with porosity and permeability increasing by 96.8% and 1280%, respectively. The fractal dimension increased with immersion time, reflecting enhanced geometric complexity of the pores. Based on mesoscopic and macroscopic experimental data, a multi-scale damage evolution model was established by introducing fractal dimension corrections into macroscopic elastic modulus and mesoscopic pore parameters. This model effectively correlates the macroscopic mechanical response with the mesoscopic structural damage evolution. It demonstrates significant importance for predicting the long-term mechanical performance and assessing the stability of water-immersed rock masses in geothermal development

Keywords

water-rock interaction / pore structure evolution / fractal dimension / acoustic emission / mechanical property / damage evolution

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