A PERCOLATION APPROACH TO DETERMINATION OF EFFECTIVE STRESS PARAMETER IN UNSATURATED SOILS

摘要

Unsaturated soil mechanics has gained wide applications in geotechnical engineering practice. Soils in their saturated state are far different from their unsaturated condition. Shear strength of unsaturated soils may be adequately described using principle of effective stress. Bishop (1959) proposed an effective stress equation for unsaturated soils. In this relationship, the contribution of suction to the effective stress is controlled by a parameter, χ, which is function of stress history, soil water content and placement conditions. Determination of this parameter is, therefore, a challenging task. In this paper, percolation theory is employed to predict the variation of effective stress parameter, χ, as a function of soil suction. In the proposed procedure, the pore size distribution of the soil is determined from SWCC (Soil Water Characteristic Curve) and a conceptual method is constructed employing percolation theory. Next, The effective stress parameter, χ, is determined directly from the conceptual model. To validate the accuracy of pore size distribution derived from SWCC, the soil water characteristic curve is reconstructed from the conceptual model. Pore size distribution was adjusted to minimize the error between the actual and predicted SWCCs. Then, the corrected pore size distribution is employed to predict the function for the effective stress parameter, χ, using the percolation-basedmodel. Finally, the results thus obtained are compared with the available experimental tests and discussed in details. The results indicate that the proposed is capable of predicting the variation of χ parameter for the range of suctions studied with a reasonable accuracy.