A practical method for solving free-surface seepage problems

Abstract Free-surface (unconfined) seepage problems are commonly encountered in geotechnical engineering. In these problems, the determination of the free surface usually requires sophisticated numerical techniques, unfamiliar to most engineers and students. Herein we present a practical finite difference method for unconfined seepage, which can be easily implemented in spreadsheets. The finite difference equations are based on the concepts of extended pressure and flux conservation. The method is illustrated by several free-surface seepage problems previously analyzed with more sophisticated numerical techniques. The proposed method eliminates the formation of matrix systems at the expenses of slower convergence rate for large problems. It has not only educational but also practical values as it applies to various engineering problems.