A general mathematical model for clay core rockfill dams

The mathematical models for clay core rockfill dams have to evaluate the history of the movements of the fill body and the pore pressures in the clay core during the construction stages and the dam operation. The first finite element models of the embankment dams were assigned to homogeneous fill in the elastic range with or without simulation of the construction sequences (Clough and Woodward 1969). The non-homogeneousness introduced by the impervious core and the transition filters were taken into account by a proper specification of the elastic Characteristics. Later on, the inelastic behaviour of the fill body were considered through the tangent Young modulus and the tangent Poisson ratio, based on hyperbolic type equations which assimilated the real stressstrain relationships ( Duncan and Chang 1970 , Kulhaway and Duncan 1972). In order to reproduce tħe critical stage developed within the dam body and to evaluate the sliding stability of the dam slopes a special type of mathematical models were set up, using the nonlinear stress-strain relationships and different failure criteria (Zienkiewicz and Cormeau 1974, Naylor 1975 ). The time parameter of the deformation phenomenon has been considered in some rheological models based on finite element schemes of viscoelastic types ( Watanabe 1975 ) or visco-elasto-plastic types (Priscu, Ionescu and Stematiu 1978). All this mathematical models were refered only to homogeneous rockfill dams, disregarding the consolidation phenomenon of the clay core. In some cases the effects of the seepage in the elastic core were considered through a field of body forces given by pore pressure gradiends, independently evaluated ( Naylor 1974 ). For the consolidation phenomenon Sandhu proposed a general variational principle concerning the seepage in linear elastic soils and used a two-field specialization to generate finite element solutions (1969, 1976 and 1977), but that procedure was not included in the embankment dam mathematical models.