MODERN THEORETICAL MODELS FOR ASSESSING THE COMBINED EFFECT OF INTERNAL PRESSURE AND SOIL LOAD ON UNDERGROUND RIGID PLASTIC PIPES

Résumé

This article analyzes the stress–strain behavior of underground plastic pipes under the simultaneous action of internal hydraulic pressure and external soil pressure. While the elastic approach based on the Lamé equations reflects the effect of internal pressure well, it cannot fully describe the interaction with the soil, ovalization, and time-dependent hyperelastic (viscoelastic) processes. Therefore, the paper studies integrated approaches that take into account combined loads — the Lamé–Marston–Spangler model, the Winkler–Pasternak spring soil model, and 3D finite element (FEM) modeling. The 3D FEM results revealed processes such as an increase in the hoop stress by 10–12% in the upper part of the pipe, an increase in the capacity energy in the lower part, and the convergence of longitudinal deformations with the lateral resistance of the soil. The article also develops practical recommendations for modeling to ensure reliable operation of pipelines under combined loading conditions.