Nonlinear Finite Difference Simulations of Cavity Decoupled Explosions in Salt and Tuff
Abstract
Nonlinear finite difference simulations are performed to model the seismic source functions for decoupled, partially coupled, and overdecoupled explosions in air-filled cavities in salt and unsaturated tuff emplacement media. The tuff simulations are performed in an 11 meter cavity under conditions similar to the Mill Yard experiment. The salt simulations are performed in a 17 meter cavity under conditions similar to the Sterling test. The maximum low frequency decoupling factor in the tuff simulations is approximately 40. The low value of the decoupling factor is the result of the low shear modulus and poor tamped coupling of this material. The maximum decoupling factor is nearly twice as large as would be expected for a linear material model because the shock wave induces pore crushing that leads to a substantial loss of energy in the nonlinear case. An important result of this research is that the low frequency source amplitude increases very slowly as the yield is increased above the yield required for full decoupling. At high frequencies, there is little difference between simulations with linear and nonlinear material models for decoupled or partially coupled explosions, except for attenuation due to pore crushing. (aw)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 30, 1989
- Accession Number
- ADA216848
Entities
People
- J. L. Stevens
- J. R. Murphy
- N. Rimer