THE DEGRADATION REGULARITY OF PHYSICAL-MECHANICAL PROPERTIES OF SANDSTONE SUBJECTED TO ACID CORROSION AND ITS ENGINEERING APPLICATION

This paper presents findings regarding the change of the typical engineering properties of sandstone in an acidic environment. Geotechnical behavior of sandstone in acid solution with different concentration was studied through lab tests. Failure model of sandstone in an acidic environment has been established based on these test results. The test results showed that the loss of the uniaxial compressive strength of sandstone in an acidic environment is proportional to the corrosion time as well as the acid solution concentration. The changing trend of the uniaxial compressive strength can be expressed by the exponential equation. The chemical reaction zone of the acid expands in sandstone with soaking time. H+ absorbed by sandstone would dissolve a large quantity of CaCO3, which results in numerous micro voids in the sandstone and increases the porosity of the sandstone. After the sandstone is dissolved by H+, the stress-strain curve of sandstone exhibits nonlinear properties; the time period of initial compaction versus yield strength becomes longer or the time period of elasticity becomes shorter. The primary failure mode of the dissolved sandstone also changes from typical fracture damage to tensile failure which is a typical characteristic of flexible materials. This paper carries out a quantitative assessment on the mechanism of micro damage caused by hydrochloric acid on sandstone and establishes a relationship between the uniaxial compressive strength, the penetration depth, the CT number, and the density of sandstone rock using the undisturbed CT scanning technique and the chemical kinetic analysis. In this paper, the diffusion model of H+ with constant and variable coefficients is established; the finite element analysis program of diffusion control equation of solution is developed with consideration of the chemical reaction of in the rock mass. Combined with the research findings on the service life influenced by acid rain in a water conservancy project, this paper provides a model of predicting service life of rock mass influenced by hydrogen ion concentration. The numerical simulation results of the service life predicted from this model are consistent with actual monitored data. This research is supported by the National Natural Science Foundation of China (NO.41172237).