Hydrodynamic Modeling of the Near-Source Environment at a Jointed Site

Abstract:

We perform near source hydrodynamic modeling of an explosive event in granite: the first Source Physics Experiment (SPE-1). The effort includes constitutive material behavior of the rock, the optimal means for representing the granite joint response, and the best modeling approach for including both the high-deformation source region and the complex material response in the near field. Each of these factors contributes to better estimates of explosion to seismic phenomena to help the verification community. We illustrate the transition of results from increasing modeling fidelity from one-dimensional (1-D) modeling which simplifies both the source geometry and the geologic character to full, detailed three-dimensional (3-D) modeling. Both levels of modeling include an accepted explosive source model and a laboratory test-based constitutive mode for the intact granite. But the full 3-D model also explicitly models the cylindrically-shaped explosive in a grout filled borehole as well as explicit representation of rock joints as contact surfaces. These modeling attributes provide for an excellent match to recorded velocity measurements in both amplitude and character. But as explicit modeling of joints is currently impractical for a large rock volume, we modify the laboratory intact properties to implicitly include the effects of joints such as in the method of Hoek and Brown to develop a credible predictive methodology for a large region.