STUDY ON THE PORE PRESSURE FACTORS OF UNSATURATED SOILS
shan hsin- yu
|Keywords:||不飽和土壤;孔隙壓力參數;土壤-水保持曲線;unsaturated soil;pore pressure factor;soil-water characteristic curve|
Classical soil mechanics has focused on the behavior of saturated soils. The major weakness associated with classical soil mechanics is the lack of understanding of the behavior of unsaturated soils and missing of a model for the moisture flux boundary condition imposed by climate conditions. However, most of the geotechnical problems which engineers encounter involve unsaturated soils above the groundwater table.The objective of the research is to study the pore pressure factor of unsaturated soils. The result of many of previous researches indicate that the value (pore pressure factor) is only between one and zero. When the soil is saturated, the value is one. For completely dry soil, the value will be zero. However, the variation of the pore pressure factor is difficult to determine within the range between one and zero. As a result, it is difficult to estimate effective stress of unsaturated soils when encountering practical engineering problems. Unless the pore pressure factor can be evaluated, the effective shear strength parameters cannot be found for an unsaturated soil; nor can the compressibility or expansibility be measured in terms of effective stress. In order to solve these problems, the main task of this research is to perform volume change test of unsaturated soils in use of specially designed consolidometor. The volume change of soils during every stage of matrix suction is used to determine the pore pressure factor in this research. Finally, by formulating simple linear equation for pore pressure factor and matrix suction in logarithmic scale, the pore pressure factor can be estimate easily.The experimental results indicate that pore pressure factor will decrease nonlinearly with saturation descent, and will approach to zero consequently. Moreover, the results show that pore pressure factor is closely related to soil-water characteristic curve and can be compute by linear equation.
|Appears in Collections:||Thesis|