Automatic simulation techniques for 3D wave propagation in geological media

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This project addresses the efficient numerical simulation of wave propagation in large geological regions. This is of crucial importance in a number of safety and sustainability related applications such as seismic failure of critical infrastructure, geological exploration or detection of underground objects. While the related complex wave reflection and refraction phenomena are inherently spatial, there is a lack of simulation techniques that can address the large-scale dynamic problem in its full complexity. In soil regions of very large extent radiation damping of outgoing deformation waves occurs, which must be represented accurately in finite computational models. Wave propagation simulation is associated with particular meshing requirements depending on the material properties and frequency content. The generation of high quality meshes for heterogeneous geological domains containing features of very different scale is highly labour intensive and requires considerable experience. The computational effort associated with nonlinear time-domain analysis of 3D wave propagation in realistic geological regions can be prohibitive.These challenges are addressed as follows. The main objective is to develop a fully automatic meshing and analysis approach for wave propagation in three-dimensional heterogeneous soil regions. Here, efficiency is of crucial importance due to the large scale of the problem. A highly flexible meshing approach will be devised, which both reduces the burden of manual mesh generation and leads to optimized numerical models both in terms of accuracy and efficiency. Structured meshes will be used, which allow for the rapid and thus highly efficient refinement of computational grids near geometrical discontinuities or in plastic zones. At the same time, the superior convergence behaviour of spectral elements for wave propagation problems will be exploited. To achieve this, a strategy for the automatic assignment of element orders in various regions based on the material properties and frequency content will be developed. Moreover, we seek to rigorously and efficiently represent radiation damping in order to keep the near field size to the required minimum dimensions. To address the above objectives, the scaled boundary finite element method (SBFEM) will be used. The latter excels in modelling waves in unbounded domains. It can be used on structured meshes straightforwardly and thus provides a potential framework for highly efficient analysis. An automatic octree / polyhedral meshing technique will be developed and specifically tailored to the requirements of wave propagation. The resulting model will be coupled to a unit-impulse-response-based formulation of the SBFEM to represent the far field. The final automatic meshing and analysis tool will facilitate the realistic simulation of three-dimensional wave radiation and scattering processes in highly heterogeneous geological domains including dynamic nonlinear phenomena.