EXPERIMENTAL STUDY OF INFLUENCE OF WATER-ROCK CHEMICAL INTERACTION ON MECHANICAL CHARACTERISTICS OF SANDSTONE

In order to investigate the influence of water-rock chemical interaction on the mechanical characteristics of sandstone,the corrosion tests are firstly carried out on the standard specimens of red sandstone taken from the site of Taoyuan hydropower project.The variations of relative qualities of samples with time are obtained as well as the variations of pH values of chemical solutions.Then,a rock triaxial testing machine is used to conduct triaxial compression tests on the red sandstones specimens soaked in six chemical solutions.The effect of chemical solutions with different pH values and ion components on the mechanical characteristics of red sandstones is studied and the influences of chemical solution on strength and deformation characteristics of red sandstones are investigated.The results indicate that the change in rock mass is related to chemical solution.There are obvious differences between different chemical solutions.As to the pH values of chemical solutions,the pH value of solution with the initial pH value equal to 13 decreases very slightly.But the pH values of other solutions finally tend to reach a regular value about 7.9.The corrosion degree is evaluated by measuring the variation of pH values for all solutions and the variation of mass of soaked specimens.According to the results of triaxial compression tests,the mechanical characteristics of rocks are related to the kinds of the chemical solutions.The pH values and ion components have a great impact on the mechanical characteristics of the red sandstone.The peak strength,residual strength and elastic modulus of the rock after corrosion are likely to decrease to a certain degree for different solutions.The failure modes of the samples under different chemical erosions with the same confining pressure have no significant discrepancy.Results obtained from laboratory tests could provide experimental data for the constitutive modelling of sandstone under chemical corrosion.