Red sandstone was selected for the study and specimens were prepared at 0°, 30°, 45° and 60° fracture inclinations and maintained in an acid solution at pH = 2. The specimens were subjected to uniaxial compression tests before and after maintenance to obtain the mechanical parameters and to observe the damage properties of the specimens. Based on the Lemaitre strain equivalence principle, a macroscopic fracture model for single-fissure rock masses and a statistical damage model for the Weibull distribution of micro-fissures were combined to derive macro-and micro-coupled damage variables for the specimens. The damage variables after acid solution corrosion are considered to derive the constitutive model for fractured red sandstone containing fractures after acid corrosion. The theoretical damage constitutive curves were compared with the experimental curves to analyse the applicability of the constitutive equation. The results show that the peak stress, peak strain and elastic modulus of the fractured specimens all vary regularly with the inclination angle, first decreasing and then increasing with the increase in the inclination angle; the peak compressive strength and elastic modulus of the fractured sandstone all tend to decrease and the peak strain tends to increase after corrosion by acid solution; the damage characteristics of the fractured sandstone are more influenced by the inclination angle and less influenced by acid corrosion; by comparing the theoretical curve with the experimental curve, the established damage constitutive model is in good agreement at the elastic deformation and plastic yielding stages. The mechanical properties of rock masses with different inclinations of fracture are quantified on the basis of the test results. The damage characteristics of rock masses with different fracture inclinations under normal and acid corrosion conditions are studied. The macro- and micro-coupled damage variables of fractured rock masses under acid corrosion are derived and validated.
Mechanical specimens of rock-like materials were prepared from cement, gypsum, quartz sand and water. After the specimens were formed, they were immersed in acid solutions of pH=2 and pH=4 for 60d and 90d respectively, and uniaxial compression tests were carried out before and after immersion to obtain mechanical parameters.Quantification of the extent of degradation of mechanical parameters and introduction of acid corrosion damage variables.Based on the Lemaitre strain equivalence principle, the Weibull distribution statistical damage model for rock-like micro-fractures was combined with a correction for damage variables that takes into account the effect of residual strength to derive a damage constitutive model under acid corrosion.The theoretical damage constitutive curves were compared with the experimental curves to analyse the applicability of the constitutive equation.The results show that after corrosion by the acid solution, the initial compression-density portion of the stress-strain curve of the specimen becomes longer and the elastic deformation phase becomes shorter,the elastic modulus, peak stress and residual strength of the specimen all decrease, and the final strain of the compression-density portion, final elastic strain, peak strain and residual strength strain values all increase,the longer the maintenance time and the more acidic the solution, the more significant the above characteristics are.Comparing the theoretical and experimental curves, the damage constitutive model, which includes acid damage and residual strength corrections, agrees well in the elastic, plastic and post-peak phases.
This study examines the mechanical properties and fracture modes of sandstone with single and double cracks under varying confining pressures through triaxial compression tests. The stress–strain curves, mechanical parameters, and fracture modes of both intact and cracked sandstone are analyzed based on experimental results. The study finds that the presence of cracks has a significant impact on the mechanical properties of sandstone, with greater damage observed with an increase in the number of cracks. The peak strength and strain of a cracked rock sample increase with the increase in crack angle. The fracture mode of sandstone is influenced by both crack angle and confining pressure. When the crack angle is small, the fracture mode is a combination of shear and tensile failure, while a large crack angle results in shear failure. Moreover, as the confining pressure increases, the degree of damage to the sandstone also increases.
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