Probabilistic approach to the evaluation of the strength of temperature-deformable sections of underground pipelines

Abstract The paper presents the results of calculating the stresses in the wall of an underground pipeline loaded with single weight in the angles of rotation on convex sections of the pipeline. Taking into account the random nature of the excess internal pressure p, the sample of the actual values of which were obtained at the pipeline operation stage, the strength of the curved sections of the main pipeline was evaluated. The necessity of individual selection of the weight of a single weight for each section of the pipeline is justified taking into account the specific law of distribution and the limits of dispersion of internal pressure in this section. Materials and methods Calculation of stresses in the pipeline and verifi ation of the fulfi lment of the strength condition of the loaded curvilinear section of main pipeline was carried out on the basis of construction norms and rules (SNiP 2.05.06-85 * Trunk pipelines). Evaluation of the strength of curvilinear sections of main pipelines in the probabilistic aspect is performed on the basis of processing random variables using methods of probability theory and nonparametric statistics. Results The implementation of the probabilistic approach made it possible to estimate the strength of the pipeline based on the actual initial data, which are of a random nature and the distribution laws specific for each section of the pipeline. The presented approach allows to provide individual selection of single weight for each of curvilinear sites at repair or reconstruction taking into account specificity of the external loading acting on the pipeline at a stage of its operation Conclusions 1. Selection of the weight of a single weight placed directly at the top of the angle of rotation of the curvilinear main pipeline section ensures a reduction in the magnitude of the maximum longitudinal stresses arising in the pipeline wall to a standard level. 2. The considered approach to the evaluation of the strength of main pipeline allows to calculate the stresses of the loaded sections of underground pipelines and justify the choice of the weight of a single cargo, taking into account the random nature of the excess internal pressure p. 3. Due to the random nature of the excess internal pressure p, the choice of the weight of the loads that ensure the fulfi lment of the strength condition for the curvilinear sections of the main pipeline must be carried out taking into account the dispersion limits and the distribution laws for the random variable p, which are individual for each of the sections. 4. Accumulated in the process of monitoring of technological parameters during the operation phase of the main pipeline, information on the values of the excess internal pressure and the limits of its change for each linear section makes it possible, based on the approach considered, to clarify the weight or to change the arrangement of the supplies at the stage of reconstruction or repair of the linear part.