Influence of Acidic Substances on Compression Deformation Characteristics of Loess

Abstract

Current research theories on acid-contaminated soils indicate that acids can alter the physical properties of soils, which in turn can affect their engineering mechanical properties. However, compressibility, one of the most important mechanical properties of loess, may be affected by acidic substances. To investigate the influence of acid on the compression properties of loess, this study uses a uniaxial compressor to investigate the changes of compression properties of loess under different acid concentrations and different acid immersion times and attempts to predict the causes of macroscopic compressibility changes from the microscopic pore changes of acid-etched loess. The test results show that when the soaking time is the same, the hydrochloric acid concentration increases from 0 to 3.0 mol/L, the compression coefficient Cc increases by 43.20–87.5%, and the compression yield stress σpc decreases by 51.36–60.86%; when the concentration of hydrochloric acid is the same, the soaking time increases from 1 day to 12 days, the compression coefficient Cc increases by 119.05–197.46%, and compressive yield stress σpc decreases by 10.67–22.02%. The microscopic images of loess soaked for 12 days at 3.0 mol/L hydrochloric acid concentration were compared with those of the original loess. The percentages of micropore, small pore, mesopore, and macropore areas of original loess were 20.90%, 79.10%, 0%, and 0%, respectively. The percentages of micropore, small pore, mesopore, and macropore areas of acid-etched loess were 6.24%, 37.21%, 1.14%, and 55.40%, respectively. The enhancement of the compressive properties of acid-etched loess is the result of the coupling of acid concentration and soaking time, and the change of macroscopic compressive properties may be related to the increase of microscopic macropore area after acid erosion. The results of this study can be used as a reference for the study of soil mechanical properties in acid-contaminated soils.

Effects of Acidic/Alkaline Contamination on the Physical and Mechanical Properties of Silty Clay

“…Anandarajah and Zhao [9] suggested that the higher strength of the flocculated structure in kaolin was due to an increase in the forces of attraction between touching particles (van der Waals forces), which will bring some additional strength to the clay structure. Gratchev et al [17,[25][26][27] and Tang et al [28] implemented the compression index and compressibility of soil obtained from a series of experiments on the geotechnical properties of soil with acidic contamination. Zhang and Wang [29] discussed the reasons for volume deformation and permeability changes caused by a sodium chloride solution through experiments and SEM observations, proving that the influences of salinity on the mechanical behavior of clays is mainly attributable to the interaction between diffused double layers.…”