Experimental study on microstructure response and mechanical properties of weak interlayer in acidic environment

Due to the infiltration of acid rain and industrial wastewater, the slope has been in an acidic environment for a long time. This reduces the stability of the slope and increases the probability of geological disasters. The weak interlayer samples were immersed in sulfuric acid solutions with different pH values for different times. X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), ion concentration monitoring, triaxial compression test, unconfined compressive tests and scanning electron microscopy (SEM) were used to study the mineral composition, mechanical strength and microstructure of the weak interlayers in various acidic environments. The results show that the main mineral components in the weak interlayers are quartz, pyrophyllite, hydromica and kaolinite. When the samples are immersed in the solution for a short time (30d), the pH value of the immersion solution is the dominant factor affecting the undrained strength of the sample. When the samples are immersed for a long time (60d or 120d), the main factor affecting the undrained strength of the sample is the immersion time. The unconfined compressive strength of the samples corroded by sulfuric acid is reduced, which is particularly evident in samples with low water content. The microstructure parameters of the samples show that with the increase of immersion time, the area of mineral particles decreased gradually and the pore ratio of samples increased gradually. The microstructure images and microstructure parameters of the samples are consistent with their macroscopic physical and mechanical properties.