Effect of pore water pH on mechanical properties of clay soil

Water quality, particularly pH, is one of the most important factors that may significantly influence soil physical and mechanical properties leading to damage of structures. This study aimed to investigate the effect of pore water pH on engineering properties of a natural clay soil. The soil was exposed to solutions with different pH values (4, 5, 6, 6.5, 9, 10, and 11) as buffered by acetate and carbonate-bicarbonate. Atterberg consistency limits, unconfined compressive strength, and shear strength parameters of the soil were measured after 90 days of exposure to the solutions. The results indicated that the unconfined compressive strength, shear strength parameters, and liquid limit of the soil increased considerably when the pore fluid had a high pH or a low pH. Thus, the results obviously showed that engineering properties of the soil greatly depend on the pH of pore water.