The article deals with design validation of a new structural design of an embankment dam, i.e. rockfill dam with seepage-control element of composite design. It consists of a reinforced concrete face (in the dam upper part) and a wide grout curtain (in the dam lower part). Analyses of the dam stress-strain state (SSS) were conducted on the example of a 235 m high dam. Numerical modeling of the dam was performed with consideration of its construction and loading sequence, as well as non-linear deformation of rockfill. Impact of rockfill deformation and grout curtain material on the dam SSS was studied. It was revealed that conditions of the reinforced concrete face operation in the considered dam structural design differ from conditions of its operation in the dam of t classical design; it is subject to not tensile but compressive longitudinal force. This effect decreases the risk of cracking in the face. However, it should be taken into account that under certain conditions the compressive longitudinal stresses in the face may exceed the concrete compressive strength, therefore, the face thickness (in the lower part) is recommended to be taken equal more than 2 m. The least safe assembly of the considered dam structural design is interface of two seepage-control elements. It is arranged with the aid of a concrete gallery located under the grout curtain. SSS of the reinforced concrete face lower part greatly depends on the grout curtain deformations. To provide the face safety the deformation modulus of the grout curtain material should be not less than that of rockfill. The grout curtain strength and SSS are mainly determined by the material deformation. At high rigidity of the curtain material there is a danger of appearance in it of tensile stresses and separation of the curtain from the rock foundation. It is recommended to arrange the grout curtain of clay-cement grouts so that deformation modulus of the curtain material does not exceed 500 МPа.