DEVELOPMENT OF A DIGITAL MODEL OF A PIPELINE IN PERMAFROST SOILS

Abstract

The work is devoted to the study of the stress-strain state of a pipeline laid in permafrost soils. The essence of the study is the development and verification of a tool for assessing the stress-strain state of a pipeline when changing the properties of the soil around the pipeline. The purpose of this study is to develop a computer model that takes into account the dependence of the mechanical properties of permafrost soils on temperature when calculating the stress-strain state of the pipeline during the destruction of thermal insulation. Research objectives: 1. development of a coupled thermal and mechanical model of a pipeline in permafrost soil in application software; 2. adding to the calculation model the dependence of soil properties on temperature; 3. adding to the calculation model a change in the volume of soil due to freezing of liquid in the soil. Adding properties of heaving soil. The introduction deals with digital and analytical coupled thermal, mechanical and hydraulic models. The choice of a software package for modeling processes is substantiated, and the relevance of such modeling is also shown. The simulation of the pipeline defrosting process is carried out using the ANSYS software, which is based on the finite element method. The article shows the developed model of the pipeline, as well as the details of setting up such a model for thermal mechanical calculation. Features such as specifying loads and boundary conditions by steps, as well as setting the relationship of these steps are given. Based on the results of the thermal calculation, it was revealed that the depth of thawing in case of violation of thermal insulation for given boundary conditions varies from three to five meters from the daytime surface of the soil. With such a spread of the boundaries of the thawing halo, the pipeline deflection varies from 0 to 300 mm, while the equivalent stresses increase from 10 to 140 MPa. To improve the model, a method is proposed for setting the properties of soil heaving using the soil linear expansion coefficient. An experimental bench is proposed for determining the values of this coefficient depending on soil moisture and temperature difference.