Experience of the construction and operation of the long linear objects shows that the change of the route thermal field occurs as a result of thermal and mechanical interaction of the underground pipelines with the environment. The consequence of these changes is the deviation of the pipeline spatial position from the design one, an increase in the longitudinal and transverse displacements and stresses, which ultimately can result in the loss of the pipeline carrying capacity and an emergency. One of the methods which allow assess the influence of thermal processes in the soil on the trunk pipelines strength reliability is monitoring of the change in the temperature field of the linear sections using thermometric wells located along the route.
The spectrum of soil temperature changes has the random nature and is individual for each section of the trunk pipelines linear part. The regularities of changes in the temperature field differ both in depth from the soil day surface and along the route of the trunk pipeline. As a result of this, the assessment of strength reliability of the trunk pipeline linear part should be based on the individual approach to each of the examined sections, depending on the depth of its laying and location on the route.
The approach described in the article allows to consider the random nature of the change in the soil temperature field at various depths from the day surface, specify the actual temperature difference for the examined section taking into account its location on the route, and to obtain more correct results when solving the tasks of the strength reliability assessment of the trunk pipelines linear part.
To increase the validity of the results of the reliability indicators calculation, it is required to perform: constant monitoring of the route temperature field of the trunk pipelines, which are at the operational stage, formation of the database of temperature values recorded on the linear part using thermometric wells, analysis and statistical processing of the results for subsequent integration into the calculation models of reliability indicators.