Abstract: With the development of industrialization and urbanization in loess regions, the problem of soil pollution caused by acid, alkali solutions in industrial wastewater, domestic sewage and rainwater with changed pH value is becoming more and more serious. Secondary disasters such as secondary subsidence may occur to different degrees under the load of surface buildings after the foundation soil is polluted. In order to find out the influence of acid-base pollution on the compression index at different pressure zones of Q3 loess, consolidation tests were carried out on intact loess samples contaminated by different concentrations of solutions. The results show that comparing the distilled water, the total deformation of acid-contaminated soil increases and the pressure section of the maximum deformation decreases; the total deformation of alkali-contaminated soil decreases and the pressure section of the maximum deformation increases. The compressibility of soil samples will change from medium to high compressibility with the increase of compressibility coefficient after acid solution contamination, but the compressive coefficient of alkali contaminated soil reduces somewhat. Compression coefficient, compression modulus, and volumetric compression coefficient of acid contaminated samples are more sensitive in medium and low pressure range less than 400 kPa, while those of the alkali contaminated samples are more sensitive under the high pressure range beyond 400 kPa. On this basis, the stress-strain relationship under confining condition is analyzed. It is found that the stress-strain curve of contaminated loess under different contamination conditions is in good agreement with the Guanry relationship.

Key words: Q3 loess, acid and alkali contamination, pressure sensitive section, compression index