Modeling the deformation process of an underwater gas pipeline under the explosive loading

The process of deformation of an underwater two-layer gas pipeline during the explosion of a nearby octogen charge is simulated. For modeling, a specially developed proprietary software package is used to solve three-dimensional dynamic problems of interaction of elastoplastic structures with compressible media, based on a single Godunov scheme of increased accuracy for calculating the joint motion of gas, liquid, and elastoplastic media. The package uses an Eulerian-Lagrangian approach with explicit identification of moving contact surfaces between different media. For each environment, three types of computational grids are used. These are Lagrangian surface meshes in the form of a continuous set of triangles for specifying the initial geometry of bodies and accompanying them during the calculation process, as well as two types of three-dimensional volumetric meshes automatically generated during the calculation process. The charge, which has a spherical shape, is initiated at its center. To describe the process of propagation of steady-state detonation, the hydrodynamic theory of detonation is used. Shock waves generated during an explosion in the surrounding liquid interact with a fragment of a two-layer pipeline and a solid bottom. Wave processes are analyzed both in the steel pipe and in the concrete shell that weighs it down. Loads on the pipeline are estimated depending on the distance to the charge and the position of the pipeline relative to the bottom. The possible destruction of both steel and concrete weight shells in areas of tensile deformations that are formed in places of the maximum bending of the pipeline is shown. It is shown that the proximity of the bottom can significantly enhance the impact of explosive loading due to the action of shock waves reflected from the bottom.