The results of an experimental study of dam-break waves for both a dry and a flooded bottom in the lower pool are compared with the first approximation of shallow-water theory. It is shown that this approximation adequately describes the height and velocity of the hydraulic jump in the lower pool for a flooded bottom, does not describe the undulations, and is inconsistent with the experimental data on the perturbation propagation velocity in the upper and, for a dry bottom, in the lower pool.Keywords: dam break, dry and flooded bottom, level-fall wave, hydraulic jump, reflection from a vertical wall.

Abstract. Methods for calculation of thermal regime and heat loss parameter for underground tunnel into surrounding sub-soil were developed in first half of XX century, when the study of complex heatmass exchange processes between underground tunnel, sub-soil and outdoor air is started. In tunnel it need to be provided a specific microclimate parameters, that requires a certain load on environmental control system. At present time there are some methods for calculation of heat loss parameter for underground tunnel. In this paper the analysis of real methods of calculation of heat losses of underground tunnel is accomplished.

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The solvability of the problem of the flows resulting from the incidence of a discontinuous wave on a bottom step is studied using a single-layer shallow water model. Solutions in which the total energy of the flow is conserved at the step and those in which it is lost at the step are considered. Regions of double and triple hystereses in the obtained self-similar solutions are found. An analogy is drawn with the problem of single-layer flow over a bottom obstacle.