Some numerical techniques for free-surface seepage analysis

Abstract Some numerical techniques are discussed applicable to the solution of unconfined seepage problems, considering both steady state and transient conditions. In particular, the procedures based on the finite element method are considered, which can be subdivided into two main groups: the so called “constant” and “variable” mesh approaches. An alternative technique is also discussed that requires a bijective mapping to be established between the physical domain (the shape of which is a priori unknown, and varies with time for transient problems) and a fixed domain having a simple (e.g. square), time independent shape. Finally, some comments are presented on the stability problems that might show up when the point of intersection between the free surface and a pervious boundary exposed to the atmosphere has to be determined.