Modellgröße und Randbedingungen bei der geohydraulischen Berechnung einer Restwasserhaltung mit der FEM

Model size and boundary conditions for geohydraulic calculation of a residual-water drainage system using the FEM.

It is rational, in excavations in the subsoil beneath the groundwater table, to embed the pit wall in a less permeable soil stratum and operate a residual-water drainage system. The Finite Element Method (FEM) can be used to determine both the influx of groundwater and the potentials and pore-water pressures relevant for various analyses of stability. Such numerical calculations require the selection of a model size and the assumption of certain boundary conditions, however. The influence of these on the results of the calculation are examined in this paper. A study has been performed for the cases of plane and axis-symmetrical states with isotropic and anisotropic subsoil, and is firstly optimised by formulating the task as a parameterised boundary value problem. Evaluation of the mathematical characteristics of the boundary value problem and dimensional analysis are then used to reduce the number of parameters. Finally, conclusions concerning the necessary model size and boundary conditions are drawn on the basis of the parameter study, and recommendations then provided for the user.