PROVIDE STRENGTH OF THE UNDERGROUND PIPELINE SECTION WITH POSITIONAL DEVIATIONS AT COMPENSATING THE DEVICES INSTALLATION

Abstract

Background. The presence of karst is one of the reasons for the deviation of the underground section of the pipeline, composed of straight pipes and insert curves, from the design position. In this case, it compresses in the longitudinal direction along the entire length of the calculated section, and the magnitude of the stresses exceeds their maximum permissible value from the standard influences and loads. Therefore, there is a need to make changes in the design of the pipeline, which could reduce its level of mechanical stress-strain state. Aims and Objectives. This paper is devoted to the study of meсhanical stress-strain state and ensure the strength of the underground part of the pipeline project in violation of the provisions of the instalation at the ends of the calculated area compensators designed for the removal of the longitudinal compressive forces in the pipe wall. Metods. Mechanical stress-strain state calculations of the selected section of the pipeline was carried out for two settlement options in violation of the provisions of the project: 1) the pipeline is made up of straight pipes and convex inserts; 2) in the middle part, where the pipeline has the greatest deviation from the project straight pipe replaced concave insert. In the third design option, the settlement is considered the pipeline composed of straight pipes and convex inserts after his return to the design position. Presented in the paper, diagrams and extremes mechanical stress-strain state pipeline characteristics are found by solving the problems: a) the ends of the calculated portion pinched the ground, so they cannot move in the longitudinally direction; b) on the ends of the counted site the compensators intended to relieve the longitudinal compressive forces in the pipe wall; c) due to failure in the functioning of the compensator the pipe can move in the longitudinal direction. Results. The calculation results are presented in the form of diagrams of the main characteristics of pipeline mechanical stress-strain state and tables, which are given extreme importance of these characteristics. Each version of the calculation concludes with an analysis of pipeline mechanical stress-strain state and evaluation of its strength in accordance with the requirements governing the operation of the main pipelines of the normative documents. As a result of the analysis of the mechanical stress-strain state and evaluation of the strength of the pipeline section, it is determined that if the design position in the pipeline is violated in which the rotation angles in the vertical plane are composed of the curves of the convex inserts, and the middle part is made of straight pipes, the installation of the compensators does not reduce the mechanical stress-strain state level, but rather leads to its growth and the emergence of potentially dangerous areas. The installation of the expansion joints reduced the mechanical stress-strain state level in the pipeline section, in which straight pipes in the middle part were replaced by concave inserts.