Keywords: dam, interaction modelling, stability, filtration, finite element analysis.

The objective of this paper is to present a complex methodology for groundwater flow and stress-strain process interaction modelling for application to dam construction and reservoir formation. The region analyzed was modelled using a three-dimensional finite element mesh, whereas the real geometry and the disposition of different geological environments were completely respected. The program PAK [1] was used and adapted for solving the problems of the fluid flow and the rock mass deformation interaction.

Using the filtration process modelling, the fields of potential, gradients, and fluid velocities were obtained for the determined boundary conditions and accepted material properties, as well as a filtration forces field as a measure of an interaction between the fluid and the soil. Filtration processes were analyzed using the differential equation of fluid flow through a porous medium for stationary and non-stationary conditions, derived on the basis of Darcy's Law for the small velocity case [2].

The filtration forces obtained were used as an input for the stress-strain analysis. The stress-strain analyses were performed using an elasto-plastic model with a critical state concept [3]. The fields of displacement, stress, elastic and plastic strain of soil were obtained using stress-strain processes modelling. The fields of all relevant values refer to the investigated space as a whole: the dam, injection curtain and the surrounding rock mass. According to the results obtained, the critical zones related to the soil stresses and strains could be identified, as well as the fluid flow gradients.

The paper presents the developed methodology that gives a very good assessment of the structure global safety. This methodology also enables localization of the critical zones for static and filtration stability, as shown in the analysis of the Lopatnica dam in Serbia. By using the results obtained, it could be concluded that the Lopatnica dam design solutions possess the required safety. Considering the potential of this methodology, it is possible to generalize it and use it for different structures.

1

M. Kojic, R. Slavkovic, M. Zivkovic, N. Grujovic, "PAK-Finite element program for static and dynamic nonlinear analysis and heat transfer", Faculty of Mechanical Engineering in Kragujevac, Kragujevac, 1998.

2

C.S. Desai, "Free surface flow through porous media using a residual procedure", in R.H. Gallagher, J.T. Oden, O.C. Zienkiewicz, T. Kawai, M. Kawahara, (Editors), "Finite Elements in Fluids", John Wiley & Sons, 5, Chapter 18, 377-392, 1984.

3

M. Kojic, K.J. Bathe, "Inelastic Analysis of Solids and Structures", Springer, Berlin Heidelberg New York, 2005.

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