An Implementation of Finite Element Method for Determining Free-Surface Seepage Problems

Free-surface determination is an important issue of groundwater seepage analysis in unconfined problems as this surface may not be prior known. Therefore, this is defined as a very highly non-linear problem, especially when including the effect of unsaturation into considering the hydraulic conductivities of soils. This study is an implementation of finite element method for solving this problem. Besides, it also considers the effect of unsaturation on the hydraulic conductivities using a popular model. Next, numerical experiments have been conducted through a range of soil types and mesh sizes. The conclusions are that two types of soils, namely fine and coarse ones, do not have a significant influence on the number of iterations. Moreover, the mesh fineness that is represented by a ratio called the area ratio (AR) has been examined to see whether the outcomes are stable or not. The percentage of the average element size over the entire calculated area is 0,1% or finer is acceptable in terms of accuracy.