Abstract. The article describes the research methodology of parametric vibrations and dynamic stability of ground thin-walled large-diameter pipeline. The equation of motion of the middle surface of the cylindrical shell element based on elastic resistance of ground. To determine the frequency of free oscillations using the assumptions of the semimomental theory of cylindrical shells and get a complete system of equations for the case of an articulated fixing of the cylindrical shell. Solving the resulting system in analytical form the expression for determining the square of the frequency of free oscillations of a thin-walled ground gas pipeline of large diameter. The methodology of the study of the dynamic stability of a gas pipeline under unsteady effects of internal operating pressure, and the parameter of the longitudinal compressive force, using Mathieu equations. With the help of the Bogolyubov-Mitropolsky techniques built area of dynamic instability in the form of Ince-Strutt diagram for different values of the internal pressure of the pipeline section, the parameter of the longitudinal compressive force, and parameter of thin-walled h / R.

Abstract. In this paper, we solve the problem of free bending vibrations of the main thin-walled large-diameter pipeline, corresponding semiunderground laying type. As a result, vibration process involves a pipeline to move the surrounding ground, which significantly affects the frequency free vibrations. The values of the natural frequencies of the pipeline will depend on the characteristics of the ground, and it's mass. The decision takes into account the impact of the attached ground mass on the free vibration frequency based on the geometrically nonlinear version of semimomental theory of average bending cylindrical shells.

This paper is based on the equation obtained earlier by V.G. Sokolov to find the frequencies of natural vibrations of straight sections of large-diameter pipelines. In this work, to take into account the effect of hydrostatic pressure on the pipeline wall from oil flowing at different speeds, the solution obtained by M.A. Ilgamov and A.S. Volmyr is used. At the same time, the effect of a stationary fluid flow on the pipeline wall is taken into account in the equation written in forces for the last term of the normal component of inertia forces. The resulting modified equation allows determining the frequency characteristics of the pipeline both according to the rod theory (without taking into account the deformation of the cross section) and according to the theory of shells (taking into account the deformation of the cross section).

Abstract. The paper presents an engineering method for calculating the weak clay base, strengthened with sandy piles reinforced along the contour. The method is based on the principle of layer-by-layer summation, which is used when designing the bases and foundations. The novelty of the suggested method lies in the taking account of the soil reaction along the pile lateral surface and the impact of external vertical loads on the vertical displacement of the base.

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