Strength of underground pipelines under seismic effects

A brief analysis of calculation methods to assess underground pipeline earthquake resistance, their advantages and disadvantages are given in the paper. The analysis of the models of underground pipeline-soil interaction under seismic (dynamic) effect is given. The coupled problems of underground pipeline-soil interaction at seismic wave propagation in a soil medium with embedded pipeline are set. One-dimensional non-stationary wave problems for the soil medium and the pipeline are solved numerically using the method of characteristics and the finite difference method. Numerical solutions are obtained in the form of a change in longitudinal stresses over time in various sections of the pipeline. An analysis of the obtained numerical solutions shows a significant dependence of longitudinal stresses on wave processes in the soil medium, dynamic stress state of soil and mechanical properties of soil and the pipeline material. A factor of a multiple increase in longitudinal stresses in the underground pipeline under its dynamic interaction with soil is revealed. It is shown that the main reason for this increase in stresses is the dynamic stress state of soil around the pipeline under its interaction with soil. The results obtained are the grounds for the development of a new regulatory calculation of underground trunk pipeline strength under seismic effect.