A STUDY ON UTILITY OF SLAKED LIME DERIVING FROM SHELL AS STABILIZER FOR ACIDIC SOILS

本研究包括以下三个实验：第一阶段是验证黄铁矿在风化过程中生化氧化的重要性，并寻找比自然氧化更快的最佳pH条件。第二阶段是通过钻孔岩心处的物理和化学不连续的痕迹来阐明酸性土壤构成的边坡的破坏机制；第三阶段是研究用破碎牡蛎壳提取的熟石灰稳定的土壤（pH <5，有机质含量>8%）的强度特征。各项试验的主要结果总结如下：(1)亚铁氧化为Fe^<2+> + 1/ 4o_2 + H^+→Fe^<3+> + l/2H_2O是黄铁矿生化氧化过程中最重要的过程，其最佳pH值为2.5 ~ 3.5。(2)对直径约65mm、长度约12m的钻孔岩心在100mm区间内进行切割，对92个钻孔岩心的含水量、pH值、电导率和燃失量进行测定，发现钻孔岩心处存在与物理化学性质不同的不连续面，可能是这些不连续面导致了边坡破坏。(3)稳定土的无侧限抗压强度与石灰掺量和养护时间成正比增加。

The present study consists of three experiments shown in the following:The first stage is to verify the importance of the biochemical oxidation of pyrite in the weathering process and to find the optimum pH condition for faster oxidation than in nature. The second stage is to clarify the failure mechanism of slope composed from acidic soils by the trace of physical and chemical discontinuities at the boring-core, and the third stage is to investigate the strength characteristics of soil (the pH value<5, the organic matter content>8%) stabilized by using slaked lime deriving from the crushed oyster shell.The main results obtained from various tests are summarized as follows:(1)The ferrous iron oxidation, given as Fe^<2+> + 1/4O_2 + H^+ → Fe^<3+> + l/2H_2O is the most important process in the biochemical oxidation of pyrite and its optimum pH value is 2.5-3.5.(2)When we cut of the boring-core with diameter of about 65mm, length of about 12m in the 100mm interval and measured the water content, pH value, electric conductivity and ignition loss of the 92 samples, it was found that there were discontinuities differed from the physical and chemical properties at the boring-core and perhaps the slope failure was generated in these discontinuities.(3)The unconfined compressive strength of stabilized soil increases in proportion to the lime additive content and curing time.