| A technique for predicting ground motions from accidental detonation of high explosives in underground ammunition storage facilities sited in rock geology was developed. This methodology does not rely on a decoupling factor applied to fully-coupled ground motions, which is a significant departure from current empirical methods. This technique allows one to account for the parameters significant to underground ammunition storage facilities including charge weight, charge distribution, and cavity size and shape. The procedure employed to develop this prediction model included the design and execution of a set of precision small-scale experiments to validate a numerical simulation model. These experiments resulted in a unique set of measurements from decoupled detonations for stress levels up to 2100 MPa. The experiments were conducted in a simulated intact and jointed rock using a well-characterized concrete. A comprehensive set of laboratory material property data are provided for the concrete. The validated numerical model was used to conduct a parameter study designed to identify the effects within the model of cavity length, cavity diameter, equivalent explosive length and diameter, and degree of venting.; The prediction technique developed in this effort defines cavity wall loading as a function of scaled distance. The cavity wall pressure, which is strongly influenced by the stagnation of the detonation products, was used to determine peak radial stress in the free-field. A material strength parameter was identified to define the appropriate range to the elastic limit boundary as developed in the model. Beyond the elastic limit the procedure provides for calculation of peak radial particle velocities from elastic plane-wave theory with appropriate attenuation. |
