Abstract: This paper investigates the effects of simulated acid rain on the strength and dissolution characteristics of lead contaminated clay, which is stabilized by GGBS-MgO (ground granulated blast furnace slag-magnesium oxide). Semi-dynamic leaching tests are conducted to measure the soil pH value, needle penetration depth, unconfined compressive strength and concentrations of lead, calcium and magnesium in leachate. Thus the effects of the initial pH of leachant, content of GGBS-MgO and lead contamination on the strength characteristics of GGBS-MgO stabilized clay are analyzed, and their effects on the cumulative mass of leached lead, calcium and magnesium and effective diffusion coefficient of lead are further determined. The results demonstrate that the unconfined compressive strength of clay using the semi-dynamic leaching tests is 2%-53% less, compared with the value under standard curing conditions for 39 days. Moreover, the highest impact on the strength of soil is found with an initial pH 2 of the leachant. Under the same content of GGBS-MgO and initial pH of leachant, the strength of the GGBS-MgO stabilized clay is approximately 12%-43% higher than that of the cement solidified clay. When the content of GGBS-MgO is 18%, the strength of clay stabilized by GGBS-MgO is almost 1.3-1.8 times of that of clay stabilized by cement. When the initial pH of leachant is 2, the pH at the specimen subsurface is approximately 50% of that when the pH values of leachant are from 3 to 7. The needle penetration depth decreases with increasing initial pH of leachant, qu and internal pH of clay. Furthermore, the relationship between needle penetration resistance and unconfined compressive strength fits unique power. In addition, the cumulative mass of leached lead, calcium and magnesium decreases with the increase of initial pH of leachant and the content of GGBS-MgO. When initial pH of leachant equals to 2, the cumulative mass of leached lead, calcium and magnesium is approximately 29-222, 1.7-4.4, 12.0-80.3 times of that when initial pH values of leachant are 3, 4, 5 and 7, respectively. Besides, when the content of GGBS-MgO is 12%, the cumulative mass is 1.1-2.0 times of that when the content is 18%. In addition, the effective diffusion coefficient of lead De decreases with the increase of the initial pH of leachant. When pH of leachant is 2, the De is 3-5 orders of magnitude higher than that of the pH values of leachant are 3, 4, 5 and 7. It is found that the De of lead contaminated clay stabilized by GGBS-MgO is lower than that of cement stabilized clay. Particularly, when the pH of leachant is 7, the De of the former one is 1-2 orders of magnitude lower than that of the later one.

Key words: ground granulated blast furnace slag-magnesium oxide (GGBS-MgO), solidification/stabilization, semi-dynamic leaching test, lead contamination, unconfined compressive strength, effective diffusion coefficient