Study On The Process And Meso-characteristics Of Acid Corrosion Of Sandstone In Acidic Environment

With the extensive application of CT technique in geotechnical engineering,it has become a new trend to explore the variation characteristics of rock internal mechanism from a microscopic perspective.In this paper,based on the accelerated laboratory test simulating the acid corrosion of sandstone under different acidic environments,the core CT scan test and the Avizo software were used to visually characterize the internal pore structure of the acid-corroded sandstone and establish a digital core.Analysis of characteristics of sandstone porosity of different position,from the perspective of mesoscopic description by acid corrosion process of sandstone,with the help of the basic principle of lattice Boltzmann and uniaxial compression test,exploring the seepage characteristic of the sandstone and corrosion by acid corrosion in the process of penetration depth change rule.The findings are as follows:(1)In the process of acid corrosion,bubbles and flocculent sediments will appear in sandstone,and the influence of acidic environment on the corrosion process was investigated by measuring the dissolution rate of cations.Comparing the core slice images obtained in the CT test,the mineral composition and particle distribution of sandstone were analyzed,and the corrosion degree of acidic solution to sandstone at different locations was judged.(2)Small core samples were taken from five different positions of the corroded sandstone,and a digital core pore model was established.It was found that the acid solution caused the most severe corrosion on the upper surface of the sandstone,followed by the lower surface,and the middle position was in the uncorroded zone.The higher the concentration of acid solution,the faster the dissolution rate of sandstone.The porosity at the lower position of rock sample in p H=1 sulfuric acid solution is 2.803%,and the porosity at the lower position of rock sample in p H=3sulfuric acid solution is 2.063%.The corrosion conditions are the same and the corrosion degree is basically the same.On the contrary,the porosity difference of different sizes will appear in the sandstone.The higher the concentration of acidic solution is,the smaller the porosity difference will be.(3)Based on the lattice Boltzmann equation,the seepage model of acid-corroded sandstone was constructed,and the change of permeability depth of sandstone with porosity under different acidic environments was compared.The penetration depths of sulfuric acid solutions with p H = 1 and p H = 3 were 4.23 mm and 3.97 mm,respectively.The test values of the penetration depth of sandstone in two acidic environments were calculated by uniaxial compression test of 4.54 mm and 3.96 mm,respectively,to verify the applicability of the seepage model constructed by lattice Boltzmann equation to simulate the penetration depth of hydrogen ion in sandstone under acid corrosion.The strength degradation law of slope engineering penetration depth changing with time in acid rain area is forecasted by an example.The research results will provide theoretical guidance for the stability analysis and durability evaluation of rock slope in acid rain area.