淋滤条件下GGBS-MgO固化铅污染黏土强度与溶出特性研究

以粒化高炉矿渣粉-氧化镁（GGBS-MgO）固化铅污染黏土为研究对象，通过半动态淋滤试验，对GGBS-MgO在酸雨作用下的强度特性及溶出特性进行研究。通过对GGBS-MgO固化铅污染黏土半动态淋滤后pH值、针刺深度、无侧限抗压强度及浸出液中Pb]、Ca]、Mg]元素浓度的测试，分析淋滤液初始pH值、掺量以及含铅不含铅对GGBS-MgO固化土强度特性的影响，讨论了初始淋滤液pH值、固化剂掺量对GGBS-MgO固化铅污染土累积铅、钙、镁溶出质量以及铅有效扩散系数的影响规律。结果表明，半动态淋滤试验使试样无侧限抗压强度qu较标准养护39 d试样降低了2%～53%，且淋滤液初始pH=2对试样qu影响最大；在相同掺量、相同淋滤液初始pH值时，GGBS-MgO固化未污染土半动态淋滤后qu较水泥固化未污染土qu提高了12%～43%；且当固化剂掺量为18%时，固化铅污染土强度特性较水泥有明显优势，约为水泥固化铅污染土强度的1.3～1.8倍；且相同配比时，淋滤液初始pH=2表层的pH值约为pH=3、4、5、7的1/2；随着淋滤液初始pH值、半动态淋滤后qu及内部pH值的增加，针刺深度减小；针贯入阻力与qu存在幂指数关系。此外，累积铅、钙、镁溶出质量随着初始淋滤液pH值、固化剂掺量的增加而减少，在初始淋滤液pH=2时，Ai,Pb、Ai,Ca、Ai,Mg分别约为pH=3、4、5和7的29～222倍、1.7～4.4倍和12.0～80.3倍；固化剂掺量为12%时的累积溶出质量约是18%掺量时的1.1～2.0倍；铅有效扩散系数De随着初始淋滤液pH值的增加而降低，初始淋滤液pH=2时的De比pH=3～7的De高约3～5个数量级；且低于水泥固化铅污染土De，当初始淋滤液pH=7时，GGBS-MgO固化土De相比于水泥固化土低1～2个数量级。

Strength and leachability of lead contaminated clay stabilized by GGBS-MgO

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.