ABSTRACT
The subject of the paper concerns an analysis of interaction between flexible pipelines with soil. The thermoplastic flexible pipes (PVC, PE) are widely used in water, waste and gas systems. Their proper functioning in complex loading conditions and durability depends on the suitable identification of loads, the strain estimate, good assortment of pipe and the appropriate installing in the soil. The character of the loads acting on the buried pipes is very complicated. They include: the soil load, surfaces loads including live loads, internal pressure and the impact of underground mining exploitation (continuous and discontinuous deformations). The conditions of pipeline laying: in the common trenches, in the areas of low-bearing soils, flood areas or in regions of landslides are important too. The calculation methods of flexible pipelines (ATV method, Scandinavian method), which are available, make it possible to analyse the characteristic cross section of pipe (the strain plane state). In this methods, the interactions between pipelines and soil during pipe deformation under loads, are represented by specific distributions of vertical and horizontal soil pressures. Far better possibilities of the flexible pipelines behaviour in soil analysis are provided by numerical methods (MES). With this methods the pipeline—soil system is analysed. The pipeline—soil system, depending on the rigidity relation of the both components (substructures), reveals different interaction. Some examples of numerical analysis of straight pipe segments (2D and 3D) as well as curve segments (3D) are presented in the paper. Spatial numerical analyses of the pipeline—soil system, which reflect particular situations, related to the functioning of pipelines under acting live loads and strongly variable soil conditions are undertaken with ZSOIL acad. ver. 11.15 software. An elasto-plastic model with isotropic strengthening (Hardening Soil Small) is used for describing soil behaviour. Results of the numerical analysis are presented as maps of displacements in the soil as well as maps of displacements of pipes.
