GEOCHEMICAL BEHAVIORAL RESEARCH OF CALCIUM IN WATER-SOIL INTERACTION SYSTEM, THREE GORGES LANDSLIDE

With the developing of water-soil interaction research in the field of landslide, it is particularly important to describe the complex geochemical reactions quantitatively and accurately. The water table changed greatly in the Three Gorges Reservoir, and it leads to series of geochemical reactions, such as ion exchange, dissolution, and precipitation. They induced changes of composition and structure of rock-soil body. The state conversion of the nature geo-environment results in slope stability problems. Loose deposit soil contains a lot of calcium, a large number of Ca²⁺ losing as water-saturated process. In order to find the influences to micro-structure of soil body that caused by chemical activity of Ca²⁺, this paper aims to study water-soil interaction system of Shiliushubao landslide in the Three Gorges Reservoir area, and the different concentration of Ca²⁺ solutions were applied for indoor saturation tests. Calcium ion was selected as the eigenfactor, and Ca2+ solutions in different alkaline were applied for indoor saturation tests. Deionized water, acid calcium solution (pH<4), neutral calcium solution (pH=7), and alkaline calcium solution (pH>10) were prepared by mixing CaCl₂, Ca(OH)₂, HCl and deionized water. And 30 days saturation tests were conducted in the cycling saturated-water device. The geochemical process was inversely simulated using PHREEQCE. Varies of reactions under the influence of Ca²⁺ were studied as well. In addition, fractal theory and ERDAS were used to quantitatively analyze the microstructure parameters and pore distribution dimensionality of the sample that collected at the beginning and ending of the tests. The results show that the carbonates dissolution, which existed as cement, interaction of clay, and ion exchange on the surface of clay controlled the whole reaction process of water-soil interaction system. This study would be significant for researching the process and mechanism of this typical and specific water-soil system of landslide in Three Gorges Reservoir. This paper offers the principle basis for improving soil quality and strengthening soil stability. It is really an innovative engineering study in preventing or remediating geo-environmental problems.