EXPERIMENTAL RESEARCH OF THE EFFECT OF LONGITUDINAL STRESSES ON PIPELINE STRESS-STRAIN STATE DURING OVERHAUL WITH LIFTING IN THE TRENCH

The relevance of this study is determined by the fact that improving the efficiency and safety of pipeline system assets is inextricably linked to the improvement of the applied technologies and calculation methods, which require revision due to the presence of certain assumptions. The objective of the study is to evaluate the influence of longitudinal stresses arising from temperature differences on the stress-strain state of the pipeline, to obtain experimental dependences of the process parameters of the overhaul of the linear section of trunk pipelines on longitudinal stresses, to perform a numerical comparison of the experimental results, and to determine the most dangerous combination of loads in the calculation scheme. Using a specially designed rig, experimental studies of the stress-strain state of the pipeline during overhaul with the lifting of the pipeline by pipelayers under the action of longitudinal forces in the pipe wall were conducted. Experimental dependences of the change in the total arising stresses on the presence of longitudinal forces and the process parameters of the overhaul of trunk pipelines on longitudinal forces in the pipe wall were obtained. It has been established that the presence of longitudenal forces in a pipeline due to temperature differences leads to changes in the process parameters of major repairs and an increase in the level of mechanical stresses in the pipe walls, which is confirmed by previously obtained analytical dependencies. The average difference in the maximum stress values with and without compressive longitudinal stresses is 11.78 %, and with and without tensile longitudinal stresses, it is 12.51 %. One of the most dangerous situations is the occurrence of tensile longitudinal forces caused by a negative temperature difference. Recommendations are given for determining the process parameters for major repairs involving trench lifting.