The influence of the piston effect in subway tunnels depends on a train speed, the geometry of a tunnel and a train, the types of air flow caused by mechanical ventilation and other variable characteristics. Tables and graphs of changes in air flows generated by the effect of the piston are presented depending on the speed of a train and the degree of fill rate of a tunnel. It is noted that the piston effect is characterized by two phases. At the first stage, the piston effect and the processes of changing physical fields are non-stationary whereas at the second stage, the processes become stable. The speed of the circulation flow created by the piston effect, in accordance with the fill factor of a tunnel, is characterised by a linear relationship; the degree of its growth is directly proportional to the speed of a train. Based on the results from the present paper it is possible to calculate the velocity and consumption of an air flow in an underground space. The maximum value of air flow carried out by the piston effect does not exceed 90-100 m 3 /s. It corresponds to the stationary phase of motion, when the tunnel filling factor α = 0.35 and train speed is in the range of 40-45 km/h. Based on the obtained numerical simulation results, technological parameters for metro ventilation systems can be calculated more accurately.

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It is established that the geothermal field of a massif around underground structures located above the neutral layer is non-stationary because of the influence of solar radiation. Below the above marked layer, the formation of the geothermal field of the subsoil is due to the process of depths and is stationary. The definition of these fields is necessary for the performance of the thermal physical calculation of the ventilation and the specification of the air consumption of the underground facilities of the metro by the thermal factor. The paper gives formulas, tables and graphs with the help of which it is possible to reliably determine the sought-for geothermal fields

Controlling the events and processes caused by fires is one of the key issues of all projects dedicated to the fire safety of tunnels. These processes are characterized by the dynamics of the propagation of high temperature, smoke and toxic combustion products around the seat of fire and in tunnels. With longitudinal ventilation, two main parameters are to be considered: the critical velocity and the backlayering length. An important impact on both parameters is exerted by the proposed system of flexible crosspieces, which, by increasing the aerodynamic resistance of a tunnel, makes it possible to reduce the speed of propagation of harmful factors of fire through the tunnel. Moreover, with certain limitations, the given crosspieces can be used to divide the tunnel into small sections what, among other things, will hinder the propagation of fire for a certain time. Thorough theoretical and experimental study of the mentioned transformable crosspieces, as well as the development of their various structures and operating principles is necessary to ensure the safety of traffic tunnels. The present article proposes a novel technology of light transformable crosspieces, which can be used in both, the existing road tunnels and the ones planned to design.

In this article presented an analysis of the hazards caused by the influence of strong fires in the road tunnels. Have been considered the main factors that affect the reliability of the results of definition of the period of time during which there is the possibility of evacuation of people. The dependence of the period of time marked by the characteristic parameters of fire: from the power of spatial localization and duration of the ascending phase of its development. The paper noted that the duration of the evacuation period, will be less than the duration of the ascending phase of development of a fire and also noted that this period tends to narrowing due to the influence of turbulent diffusion fluxes. In this paper it is assumed that the turbulent diffusion fluxes occur between the zones in which the ruling are toxic carbon gases of fire and fresh ventilation air flow.