Improvement of Calculation for Phreatic Lines in Small Earth Dams

Abstract

In recent years, many small earth dams have been retrofitted because of deterioration. The phreatic lines in small earth dams with sloping cores are geometrically calculated with the sectional shape of embankment, the water elevation and the permeability of soil materials in the current design. However, there is possibility that actual phreatic lines and calculated ones are different because of the assumption that the foundation ground is impermeable. In this study, the problems of the calculation method for phreatic line in the current design have been organized based on the results of FEM analysis. As a result, it was found that when the permeability of the sloping core is low, the phreatic line calculated by the design calculation is on the dangerous side, and that the seepage flow of the foundation soil affects the phreatic line. To solve these two problems, we proposed methods to reduce the calculation error of the current design by using functions that include the permeability of each embankment material and to obtain results that are closer to the actual phreatic lines.