| Summary: | 碩士 === 國立成功大學 === 水利及海洋工程學系碩博士班 === 95 === In this study we discuss the consolidation behavior of unsaturated soils bearing two immiscible fluids. Based on the results of Tuncay and Corapcioglus (1996) using the method of microscopic volume-averaging. We used the data obtained by Chen, et al. (1999) from experimental results of two-fluid flow, to estimate the parameters for water retention curve and hydraulic conductivity functions. The unsaturated soil examined here is assumed to have a free drainage surface on its top and an impervious surface on its base. Since lateral displacements are typically much smaller as compared to vertical displacements during the process of consolidation, the problem of one dimensional (vertical, z axle direction) representation is considered in the study. The system of two immiscible fluids considered her includes air-oil, air-water, and oil-water. Lastly, the influence of the air phase on water flow is neglected following the traditional Richards’ assumption.
Two soils, Columbia fine sandy loam and Lincoln sand were test numerically. Our numerical results show that porosity change and the total settlement have a close relation to the bulk modulus of soils. Columbia fine sandy loam is the most prone to squeeze the pore fluids. The amount of fluids expelled diminishes as permeability decreases. On the other hand, Lincoln sand settles largest. When the bulk modulus becomes greater, the settlement decreases more. The porosity was found to have the same trend as the amount of the settlement.
In addition, the saturation of the nonwetting fluid phase and the porosity are affected by the consolidation time. If the soils bear the stress which acts on the top longer, changes in the saturation of the nonwetting fluid phase and the porosity become more obvious. Oppositely, the soils bear the stress which acts on the top shorter, those changes are not obvious.
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