Coupled underground blast simulation using a 2D axisymmetric Lagrangian Finite Difference Time Domain solver with a Perfectly Matched Layer

Blast induced soil vibrations can cause structural damage even at large distances from the source, causing the need for accurate prediction methods. The occurrence of shock waves and the high strain rates and deformations call for the use of hydrocodes in the proximity of an explosion. At larger distance, the use of a more cost effective linear elastic calculation tool is preferred. A coupled numerical model is proposed, which combines a 2D axisymmetric Finite Difference Time Domain model in Autodyn with a frequency domain linear elastic method. The Autodyn model uses a coupled Eulerian-ALE-Lagrangian solver and is truncated in the linear elastic hydrocode domain. Spurious reflections are avoided by adding an unsplit field PerfectlyMatched Layer to the truncated hydrocode domain. The results at an interface in the linear elastic hydrocode domain are used to compute results in the far field, based on the dynamic reciprocity theorem and the Green's functions of a layered elastic halfspace. The methodology is validated against a linear elastic reference solution and applied to a small subsurface explosion in a non elastic soil. The blast induced vibrations are determined at distances up to 200 m from the source and are compared to empirical reference results.