Introduction. Several types of embankment dams are used in the hydraulic engineering practice. However, the choice of a dam is individual for each hydraulic engineering project, as it takes account of specific features and natural conditions. This paper compares two types of rockfill dams (the one having a concrete face and the other having an asphalt-concrete diaphragm) in relation to the Mullalakh HPP on the Pskem River in the Republic of Uzbekistan. The dam height is 85 m. The comparison was performed from the standpoint of the dam performance in case of exposure to static forces and high seismicity. Materials and methods. The analysis of (1) the stress-strain state (SSS), (2) the stability of slopes exposed to regular and irregular load combinations was conducted for two types of dams. All calculations were performed in the two-dimensional domain. The analysis of the stress-strain state took account of the non-linear behavior of the soil ground and the contact interaction between structural elements. Seismic loads, included into the scope of irregular loads, were identified using the response spectrum method applied to particular periods and self-oscillation modes. Slope stability was analyzed with regard for the stress state of soils identified in the course of SSS calculations. Results. Each type of embankment dams has its specific features. The asphalt diaphragm dam is worse at perceiving high seismic loads. Its SSS during an earthquake features strength loss and emergence of soil discontinuity zones. The disadvantage of a concrete face dam is the insufficient safety of its anti-seepage element. Supplementary measures are needed to ensure the appropriate stress state of the face. Another finding is that the slopes of both types of dam do not demonstrate a sufficient stability factor, if the slope ratio equals to 1.5 during a 9-point earthquake. Conclusions. In high seismicity regions, a concrete faced dam demonstrates better performance than the asphalt diaphragm dam if both are exposed to static and seismic forces.

Влияние поэтапности возведения каменно-набросной плотины на напряжѐннодеформированное состояние еѐ железобетонного экрана Национальный исследовательский Московский государственный строительный университет (Россия, Москва

Introduction. Rockfill deformations are developed during long time. It is known that most intensive they are during construction period, but their increment continues also during operation period due to creep. Therefore, creep may affect the reinforced concrete face stress-strain state. Nevertheless, search for the scientific and technical information showed that the problem of creep impact on the face strength is poorly studied. Materials and methods. Studies of stress-strain state were conducted with the aid of numerical modeling by finite element method. They were carried out on the example of in-situ Toulnustouc dam, which deformations during the operation period are known by the results of field measurements. For simulation of the time-dependent dam, deformation increment process there was chosen a rheological model of soil and a technique was worked out for calculating the dam stress-strain state. At plotting the rheological model, the use was made of the simplest exponential relationship of time-dependent deformations. Results. The parameters of the rockfill model were determined by selection from condition of matching between the dam design displacements and the field data. For the considered dam, the rockfill creep has not resulted in cardinal changes in the reinforced concrete face stress-strain state. Conclusion. It was revealed that increase of the dam settlements due to creep has a favorable effect: they create additional compressive longitudinal force in the face.