Methodology and the results of numerical modeling of stress-strain state (SSS) of an earth-rockfill dam are considered, where after a failure of the clay core there was created a new seepagecontrol element presented by a clay-cement concrete wall. Calculations were conducted on the example of the dam section of Kureyka HPP, where emergency situation occurred in 1992. For repairs of the 25 high dam in the core and in the foundation there was arranged a 35 m deep wall made of bored piles. SSS analyses of the dam were conducted with use of the computer program elaborated by the author. This permitted consideration in the analyses of a number of important factors such as the sequence of the dam and the wall construction, non-linearity of soils deformation, their subsidence as well as timedependent variation of seepage forces. Seepage calculations showed that load on the piles from seepage flow is formed over a long time due to the durable process of the wall construction. If piles are arranged sequentially, one pile after another, during this time clay-cement concrete acquires about 50 % of design strength. If the wall is constructed in 2 stages, clay-cement concrete acquires about 80 % of its strength. SSS analyses showed that the wall in the failed dam performs in complicated conditions: due to a non-uniform structure of soil mass, it is subject to complicated bending deformations. To avoid the appearance of tensile stresses in the wall it is recommended to make the wall of plastic clay-cement concrete whose deformation is close to deformation of soils.