Écoulement, déformation et stabilité dans les digues en terre

This report deals primarily with the deformation problem in classical sense of this word, i. e., with changes of geometrical characteristics of the considered medium, but also at the certain level, with changes of hydraulic characteristics of this medium, being expressed primarily by conductivity K. The deformations are considered due to two characteristic conditions: a) without change of masses between phases which are transported in the interspace of the solid matrix; b) with change of masses (especially subsoil, mechanic and chemical erosion, and, briefly seepage). In the first case, the water action has essentially a dynamic nature being determined by filtration force which is generated by flow. This force represents a term in the generalized Navier's equation (Eq. 1) which is discussed in this paper. The generalized Navier's equation contains also the effective stresses whose relationship to the deformation is determined by rheological models. This relationship has, in general case, to involve elasto-visco-plastic properties of the considered medium. A model, proposed by Brzosky (1969), describing all these characteristics including the action of filtration water too, is treated briefly in this paper. The practical application of such a generalized model is faced with numerous difficulties both experimental and mathematical. Because of this, some simplifications of rheological model used have been introduced (Tabl. 1) considering soil either as an elasto-plastic body (small deformations) or as a rigid-perfectly plastic body (big deformations) or even as a perfectly elastic body (small deformations) using sometimes modified material constants. The problem of the medium stability is treated from the standpoint of view of continuum mechanics as a limiting case of big deformation where the system is transforming into a mechanism kinematically labile. The medium model has to be essentially different than this one at the flow without mass changes, since the compression as well as the reduction of effective stresses can appear here (shown by a series of examples, see Figs 4 and 5, obtained at the Hydraulic Laboratory, Fac. of Civil Eng., Belgrade). In the scope of the analysis of chemical erosion, the influences of clay and suspension characteristics to the nature of the process, adding some original experiences, have been considered