Experimental study on the influence of seawater corrosion on the physical and mechanical properties and microstructural failure behavior of sandstone

In this study, experimental tests were conducted on sandstone specimens to study the influence of seawater corrosion on their physical and mechanical properties as well as failure behavior.Different concentrations of simulated seawater solutions were prepared based on seawater sampling data from the vicinity of the Shenzhen cross-harbor tunnel.Sandstone specimens were first treated with corrosion immersion in these solutions for different times before they were subjected to uniaxial compression tests.The acoustic emission and scanning electron microscope(SEM)techniques were employed to investigate damage and microstructural evolutions of the corroded sandstone.The results show that as the concentration of corrosive solution increases, the surface of sandstone specimens peel off earlier, the area is larger, and there is a slight increase in specimen density.The peak stress and elastic modulus both decrease with increasing corrosion time, but the magnitude and rate of decrease are different.With the increase of corrosion time and concentration, the active period of acoustic emission events increased in all sandstone specimens, except for the ones in the high concentration group, where the active period of acoustic emission events was shortened after 45 d of corrosion.SEM results show that with increase of corrosion time and concentration, the internal microdefects in the sandstone specimens progressively developed, and the microstructures gradually loosened.Furthermore, the area of honeycomb corrosion area increased in size and the area of white crystallization of salt ions gradually expanded.