Introduction. One of the main principles in designing modern ultra-high rockfill dams with reinforced concrete face is the principle of zoning rockfill of various quality in the dam body. It envisages that rockfill in the shell upper part should be compacted very carefully in order to minimize to the maximum the deflections of the reinforced concrete face. In the shell lower part it is allowed placing heterogeneous rockfill with less degree of compaction. Analysis of the results of field observations over settlements of the already constructed dams shows that this pattern of zoning may lead to considerable irregularity in distribution of rockfill deformation moduli between the upstream and the downstream parts of the dam. Numerical modeling of the existing Aguamilpa dam carried out by use arlier showed that this effect may be caused by unfavorable stress-strain state of the reinforced concrete face threatening with crack formation. Were come ended using dams of homogenous structure. However, this conclusion caused doubts of some experts. More detailed studies who see results are described in this article were conducted in order to confirm or disprove this conclusion. Materials and methods. The studies were conducted by finite element method on the example of 100 m high rockfill dam. Different alternatives of rockfill deformation properties in the shell upstream and downstream parts were considered. Results. Analysis of the results of studies confirmed the conclusions made earlier about the features of the rockfill dam reinforced concrete face stress-strain state. It was revealed that increase of rockfill deformation in the dam shell downstream part leads to appearance of additional tensile longitudinal force in the face. It increases the risk of appearance of through transversal cracks in the face. However, the heterogeneous structure of the dam shell may not have a decisive impact on stress values because the value of bending moment plays a great role. Conclusions. The results of the fulfilled study as well as modern dam construction practice show the necessity of modifying the traditional pattern of rockfill zoning in the dam body. It is necessary to provide decrease of differences in rockfill deformation of the upstream and downstream parts of the dam.

Introduction. In 1971, “Schedule of multi-purpose use and protection of water resources of the basin of the Belaya River” envisaged construction of a cascade of 10 waterworks facilities, subdivided in 4 sections. Nizhne-Suyanskiy Waterworks Facility was planned for construction in the third section, the most lucrative in terms of energetic utilization. However, of the three HPPs planned in this section: Varyazhskaya, Nizhne-Suyanskaya and Pavlovskaya HPP, for the time being, only Pavlovskaya HPP has been built. Nizhne-Suyanskiy Waterworks Facility had the mission to solve water household, energy and socio-economic problems. Materials and methods. Initial material for the study were the results of the “Substantiation of the investment in the construction of Nizhne-Suyanskiy Waterworks Facility in the Ufa River in the Republic of Bashkortostan” prepared by ОJSC Energy Engineering Centre of Volga Region. Based on the retrieved data, the following analyses were made: a theoretical analysis, an estimate substantiation; subsequently, conclusions were put down based on the obtained results. Results. The optimum solution is a comprehensive waterworks facility, since Nizhne-Suyanskaya HPP will allow for improvement of the electrical power supply of the consumers of the NE part of the Bashkir power supply network. The construction of Nizhne-Suyanskiy Waterworks Facility will enable the control of the water influx to the water storage basin of Pavlovskaya HPP allowing for its increased generation power. The construction of the waterworks facility is supposed to carry out in 2 stages. The first stage will be the erection of a concrete overflow weir as a single unit with the HPP building. The second stage will be the construction of a soil dam of local construction materials, that is: dam body of sand and gravel soil, PFU core of loamy soil. Simultaneously with the soil dam, on the right bank a solid blind concrete weir will be erected. Conclusions. Nizhne-Suyanskiy Waterworks Facility unfortunately was not built. Feasibility studies have demonstrated a rate of return of the waterworks facility of 12.8 %, the value being a little higher than the standard one. This justifies investment in Nizhne-Suyanskiy Waterworks Facility. The basic feasibility factors of the construction of the waterworks facility are: Federal support, project engagement of the executive authority of the Republic of Bashkortostan and PJSC RusHydro, as well as availability of free investment funds.