Monitoring of gas pipelines provides data necessary to justify the minimum value of the safety factor. Stresses in a gas pipeline made of reinforced polyethylene pipes with local soil heaving are evaluated with the use of a three-point diagram of loading by a concentrated force of a beam with a thin annular section. It is obvious from the calculations that the magnitude of axial stresses under the influence of soil heaving is far from critical. The safety factor is twice as high as the normative value.

This article describes the effect of carbon black P505 on the bending strength of epoxy resin ED-20. Studies of the effect of the filler concentration of carbon black P505 on the bending characteristics of the epoxy resin composite ED-20 were carried out at temperatures of +23 and -60 °C. Three times decrease in flexural strength and four times in deformability has been observed. When test temperature drops to -60°C, indicators of strength and deformation at failure remain unchanged.

Model experimental studies have been carried out and the cause of emergencies with pipes in protective cases used in the construction of pipelines has been identified. The design of a protective case has been developed, which excludes deformation or destruction of the pipeline when water freezes in the annulus. Model tests of the pipeline in the case, using polyethylene foam as an element that compensates for the expansion of water during freezing, showed complete exclusion of deformation of the pipeline during freezing. The developed design has shown its efficiency and possibility of widespread use to increase the reliability of pipelines in protective cases operating at temperature below freeezing point.

The article presents the test results of samples of welded joints of polyethylene pipes for crack resistance at various temperatures. It is shown that in the weld zone a decrease in the stress intensity factor to 27% is observed in comparison with the main material.