Experimental Research On Corrosion Progressive And Physical-mechanical Characteristic Of Sandstone Subjected To Acid Rain

In recent years, with the rapid development of national economic construction, the production and living of human has caused severe damage to the environment, and environmental pollution is the important research subject for environmental geotechnical engineering discipline to face. In the atmosphere acid gas has a sharp increase, which can lead to acid rain. Acidic environment will seriously affect the physical and mechanical properties of the rock. Therefore, the paper simulates the indoor accelerated corrosion test with adopting HCl solution of the PH value of 2, 3.5 and 5. With the definition of physical quantity and physical-mechanical parameters of ultrasonic testing, the change rule of physical and chemical properties of the rock sample is quantitatively analyzed in the process of corrosion. The influence of physical and mechanical parameters of rock sample on chemical damage is analyzed With CT images and CT number. The main conclusions are as follows:1. In the process of the corrosion of different concentration of HCl solution, the changing of mass of the rock sample, dissolution rate and porosity showes obvious phases. The porosity increases rapidly with increasing of the mass loss rate in 0 to 30 and 70 to 90 days. From 30 to 60 days the mass loss rate decreases, and the porosity increases slowly. Each stage of the dissolution rate showed a trend of increase first,and then decreases.2. Using ultrasonic testing technology measures the soaked rock specimens in different concentration of HCl solution. It finds that the changing of longitudinal wave velocity and amplitude is more obvious for wet rock sample in the different stages of corrosion. Its change rule is as follows: the wave velocity gradient is bigger in 0 to 30 days. After wave velocity increases slowly, and it tends to be stable in 70 to 90 days.3. With different concentration of HCl solution to tracking and observation concentrations of H+, Na+, Ca2+, K+, and Mg2+, it indicates that PH value gradually increases with immersion time in the different initial concentration of HCl solution. The cationic dissolution rate presents phase characteristics with the concentration of HCl solution. In the first phase, the maximum of Na+ dissolution rate is 264.78 mol/d in early days for HCl solution of the PH value of 2, and it is up to maximum in the medium term for HCl solution of the PH value of 3.5 and 5. The Ca2+ dissolution rate is up to 489.50 mol/d in HCl solution of PH value of 2, and it is respectively five and four times as large as HCl solution of PH value of 3.5 and 5.4. The uniaxial compression tests finds that the stress-strain curve of corrosion rock sample on nonlinear segment increases, and the time of occurring overall damage is prolonged. Chemical corrosion makes compressive strength and elastic modulus reduce, and the mechanical properties degradation of rock. The CT scanning results discovers that the rock samples occurs chemical damage by the corrosive effect of solution. In different slices and measurement area, the damage variable shows the regional characteristics, and its minimal is in the middle of scanning layer.