Ontogenetic modeling and numerical simulation of soft rock damage considering chemical correlation

Abstract

Soft rocks are significant in geo-engineering. It is important to consider the effect of chemical correlation on damage ontology modeling of soft rocks, particularly for red sandstone. Chemical correlation may significantly impact their mechanical properties and damage behavior. The objective of this study was to investigate the creep mechanical behavior of red sandstone under the influence of water-rock chemical corrosion damage using Na₂SO₄ solution as a chemical corrosion medium for groundwater. Solutions with different concentrations and pH values were developed, and semi-open immersion tests and uniaxial compression tests were conducted to understand the changes in porosity, longitudinal wave velocity, and long-term strength of red sandstone specimens. This analysis took into account the water-rock chemical corrosion effect. A model for the intrinsic structure of fractional-order creep damage was built and fitted for study in water-rock chemical corrosion environments. The results indicated that the porosity of the red sandstone specimens increases with higher acidity and alkalinity levels and higher concentrations of the chemical medium solution. Additionally, the longitudinal wave velocity of the specimens decreases with these same factors. The longitudinal wave velocity was 2.439 m/s at a pH of 3 in a 0.10 mol/L solution, and the porosity of the red sandstone specimens was similarly at its highest level at 9.97%. Strongly acidic and alkaline solutions cause more chemical deterioration in red sandstone. The highest chemical damage value at a concentration of 0.10 mol/L was 0.196 at a pH of 3, which was 0.024 more than at a pH of 5. The specimens experienced more severe accelerated creep deformation in strong acid and alkaline environments, resulting in varying degrees of peak stress reduction. The long-term strength was between 60% and 70% of the short-term strength. The damage intrinsic model had a tiny and well-fitted error when compared to the test data. The prediction of creep deformation caused by chemical corrosion of red sandstone in water can be achieved by creating an ontological model of red sandstone damage through numerical simulation.