PSI - Issue 36

352 L. Poberezhna et al. / Procedia Structural Integrity 36 (2022) 350–355 L. Poberezhna, V. Markhalevych, L. Poberezhny et al. / Structural Integrity Procedia 00 (2021) 000 – 000

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gas pipelines in Ukraine (Kryzhanivskyi and Nykyforchyn (2011), Poberezhny et al. (2019a, 2019b), Zvirko et al. (2019), Nykyforchyn et al. (2021)). Therefore, recently this problem in Ukraine is given considerable attention. One of the main factors that must be taken into account when diagnosing the technical condition of pipelines is the possible degradation of pipes. Here we must distinguish between the degradation of their surfaces and the material « in volume » . The first case involves damage to the surface due to mechanical, corrosive, and other factors, and the second case - the deterioration of the properties of all metal or its volume, commensurate with the characteristic size of the pipe (for example, wall thickness or bottom of the pipe). The reason for this may be both structural and phase changes and the development of damage (Zvirko et al., (2016), Maruschak et al. (2014, 2016), Okipnyi et al. (2018)). This calls into question the continued safe operation of the pipeline even in the absence of macro defects. Long-time exploited tubular steels also have an increased sensitivity to corrosion and mechanical degradation in operating environments (ground electrolyte, produced water, etc.) (Poberezhny et al. (2019a, 2019b), Kryzhanivskyi et al. (2019), Khoma et al. (2021)). Access to energy affects civilians’ ability to heat and light their homes, store and prepare food, and carry out regular family and economic activities. The availability of energy sources has also been impacted by measures introduced by the sides and by the conduct of hostilities in populated areas, with regular damage to infrastructure remaining the most serious problem. Similar to the water infrastructure, the electrical power supply and gas lines provide service to communities on both sides of the contact line, often crossing the contact line. Gas company representatives in Kyiv confirmed claims made by interlocutors regarding the shutting down of gas supplies from government- controlled areas to “LPR” -controlled Pervomaisk. Such breaking of ties affects people on both sides of the contact line. More than 16,000 people in the government-controlled towns of Marinka and Krasnohorivka in the Donetsk region have been without gas since summer 2014 when a gas pipeline was damaged. Similarly, since September 2015, residents of government-controlled Trokhizbenka in the Luhansk region have been living without gas after shelling in the vicinity of “LPR” - controlled Sokilnyky. The pipeline crosses through “LPR” -controlled areas where the security conditions have precluded a damage assessment (OSCE Reports (2014-2021)).

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Fig. 2. Damages for gas pipelines a result of artillery shelling in Donetsk and Lugansk regions in 2015-2016:a - Kramatorsk-Donetsk main pipeline, 2015, b- Krasnyi Shakhtar, 2016.

It is known that in some sections of the gas pipelines of the Private Joint-Stock Company « Ukrtransgaz » a discrepancy in the depth of the project was found. That is, pipelines may be partially exposed during operation due to soil erosion, and they also tend to lose stability due to various factors (pressure, temperature, soil water saturation, etc.) and rise (bulge or float) (Rajeev and Kodikara (2011), Kouretzis et al. (2014), Poberezhny et al. (2017)). Also, there are known facts of laying pipelines in the process of their construction not on the design marks, due to the « low culture » of construction, ie, when the pipeline in some areas was laid in a trench, the depth of which did not correspond to the project. Further operation of such pipelines may be endangered by the pipeline coming to the surface and mechanical damage to the insulation and the body of the pipe. When firing from artillery systems of various calibers there is an increased risk of critical damage to such pipelines (Fig. 3). Therefore, to ensure reliable operation of the pipeline, which has raised sections, it is necessary to lower these sections to the design marks. In